Rick's Free Auto Repair Advice » Alero

Intermittent problems on GM vehicles

Rick — Thu, 08 Sep 2011 21:23:07 +0000

GM vehicles from the mid ’90′s to the present are known for faulty ignition switches. The problems are almost always intermittent. Intermittent starting, dying while driving, A/C to start blowing warm air or for the blower fan to stop (depending on which GM model we’re talking about), along with an ABS light. In fact, any time you see erratic or intermittent problems that could be electtrical in nature on a GM vehicle, you should immediately suspect the ignition switch. Always test the igntion switch during an intermittent problem to see if the switch is providing power (use a meter).Or, wiggle the wires going to the switch. GM techs replace so many of these that it’s almost automatic for them to head there first

In the case of the A/C the problem is usually the ignition switch heating up and not providing power to the A/C clutch and the ABS computer. If you want to diagnose the problem, buy a wiring diagram for your vehicle form eautorepair.net or alldata.com (there are way to many GM models to list their wiring diagrams here) and test for power at the switched terminals when the problem happens. Or, just replace the ignition switch.

For more information on this repair or any others for your vehicle, buy an online subscription to either Alldatadiy.com or eautorepair.net. Click on this link to compare the two services: Compare Alldata and Eautorepair.

If you just need information for a single repair and want to save money,eautorepair offers a lower price 1-week subscription for only $11.99. Or, if you’ll be working on this vehicle in the future, you can buy a 1-year subscription (Alldatadiy.com for $26.99, or eautorepair.net $29.99)

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

P0332, Circuit Low Input (Bank 2) on GM products

Rick — Tue, 06 Sep 2011 04:10:36 +0000

Also P0335 and P0340

If you think you should replace the knock sensor after getting this code, think again. This is a perfect example of where a sensor can be telling the truth and the root cause of the problem is somewhere else. Here’s the scoop. Most late model engine use variable valve timing to change the opening and closing timing of the valves. The device that actually changes the valve timing is called the cam phaser (yeah, like on Star Treck). Some cam phasers use oil pressure to rotate the camshaft slightly to change the timing. That’s great when it’s working well. But if you’ve changed your own oil and used a viscosity that’s different from the manufacturer’s recommendations, you can screw up the phaser. For example, some people don’t believe the manufacturer’s recommendation to use 5W-30. So they change their oil with 10W-30. The slightly thicker oil can cause the phaser to respond more slowly to computer commands. And when the cam is out of phase from the commanded position, you can get pre-ignition, or pinging. Yup, if you used this oil and now have this trouble code, point your finger right at yourself.

The same holds true if you think you can get away with not changing your oil on time. Think sludge buildup isn’t a problem? Well guess what, sludge in a cam phaser can also cause trouble codes.

If you’re getting these codes and think it might be caused by oil, change your oil and filter and drive the vehicle first. Perhaps the clean oil can clear out the passages.

Here are a few other things that can cause this trouble code:

Check the electrical connector on the cam phaser. If you see oily buildup, disconnect the connector and check inside. Oil can sometimes seep into the connector and that would give false readings.

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

A/C doesn’t work and ABS light on

Rick — Thu, 01 Sep 2011 17:53:39 +0000

GM vehicles are known for faulty ignition switches. The problems are almost always intermittent. One common symptom is for the A/C to start blowing warm air or for the blower fan to stop (depending on which GM model we’re talking about), along with an ABS light. The problem is usually the ignition switch heating up and not providing power to the A/C clutch and the ABS computer. If you want to diagnose the problem, buy a wiring diagram for your vehicle form eautorepair.net or alldata.com (there are way to many GM models to list their wiring diagrams here) and test for power at the switched terminals when the problem happens. Or, just replace the ignition switch.

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

Turn Signals Problems on Malibu, Impala, Alero, Cutlass, Grand Am, Monte Carlo, Saturn Vue, Chevy S Trucks, Chevy T Trucks, Corvette

Rick — Sun, 13 Mar 2011 18:14:29 +0000

Turn Signals Problems on Malibu, Impala, Alero, Cutlass, Grand Am, Monte Carlo, Saturn Vue, Chevy S Trucks, Chevy T Trucks, Corvette

The GM vehicles above all seem to have a common problem with turn signals. The problem may show up as the following symptoms:

No turn signal operation
Rapid flash even though no bulbs are burned out
Flasher clicks even though turn signal isn’t on
Intermittent turn signal or flasher operation

The source of the problem is usually a faulty Hazard Warning Switch. Yes, you read that correctly. All turn signal operations flow through that switch and it seems GM may have under-engineered the electrical contacts in that switch. Some shops report that even after swapping out the switch, the problem remains and they must replace the entire turn signal mechanism (called the Multifunction Switch). However, dealers report extremely high sales of these Hazard Warning Switches. The dealer list price on the Hazard Switch is about $30. However, Dorman Products makes aftermarket replacements that are half the price of the GM part and are a direct fit for the factory switch. But, if you shop on Amazon you may find AC Delco parts (made by GM) for the same price as Dorman.
To replace the switch you’ll have to remove the bezels and trim panels. I suggest a subscription to Alldata because they show much better interior trim removal diagrams than eautorepair.net.
I’m listing some applications, part numbers, and links. But please double check before you buy to make the part is for your vehicle

1997-2005 Chevrolet Malibu

2000-2005 Chevrolet Impala

1999-2004 Oldsmobile Alero and Cutlass

1999-2005 Pontiac Grand Am

2000-2005 Chevrolet Monte Carlo

1997-2004 Corvette

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

ABS and TRAC OFF lights on GM vehicles

Rick — Sun, 27 Dec 2009 02:39:30 +0000

Shops are reporting huge failure rates on ABS sensors in some late model GM vehicles where the ABS sensor is integrated with the wheel bearing/hub. These sensors are in two styles. One style bolts the sensor directly on the wheel bearing. The sensor counts the notches on the ABS tone ring inside the wheel bearing. The clearance between the sensor and the tone ring is critical. The problem occurs when rust builds up between the sensor and the wheel bearing. This phenomenon is called “rust jacking,” where the rust literally pushes the sensor upwards, increasing the gap between the sensor and the tone ring to the point where it reads intermittently. If you have this style sensor, remove it and lightly sand the rust (lightly being the key word). Then apply a light coat of marine grease on the bare metal and re-assemble. You may want to try applying a thin bead of RTV silicone around the outer edge to prevent water from getting under the sensor.

The second and more common style has the ABS sensor built into the bearing/hub. This unit CANNOT be serviced. You must replace the entire bearing/hub.

Buy a new wheel bearing with new ABS sensor already installed here

When either type of sensor goes on the fritz, it lights up the ABS light AND turns off the Traction Control System. That’s because the traction control system gets all its information from the ABS computer. No input means a shutdown of the entire system. Plus, this will set a code in the PCM.

Get a new Timken wheel bearing with hub and ABS sensor for these vehicles

CHEVROLET CLASSIC (2004 – 2005)
CHEVROLET MALIBU (1997 – 2003)
OLDSMOBILE ALERO (1999 – 2004)
OLDSMOBILE CUTLASS (1997 – 1999)
OLDSMOBILE CUTLASS GLS 1997
OLDSMOBILE CUTLASS SUPREME 1997
OLDSMOBILE CUTLASS SUPREME SL 1997
PONTIAC GRAND AM (1999 – 2004)
PONTIAC GRAND AM GT 2005
PONTIAC GRAND AM GT1 2005
PONTIAC GRAND AM SE 2005

GM is also having a huge failure rate on the wiring harness that goes from the ABS computer to the sensors. The harness can short to ground. Because the harness must flex with each movement of the lower control arm, the harness can also develop an open condition where the ABS signals never reach the ABS computer. This is such a large problem that aftermarket supplier Dorman now makes replacement wiring harnesses for about half the price of the GM version.

Get an aftermarket ABS Wiring Harness for the front left sensor on these vehicles.

2005-97 Chevrolet Malibu;
1998-97 Oldsmobile Achieva;
2003-99 Oldsmobile Alero;
2005-99 Pontiac Grand Am
Dorman Part #970-008

Get an aftermarket ABS Wiring Harness for the front right sensor on these vehicles.

2005-97 Chevrolet Malibu;
1998-97 Oldsmobile Achieva;
2003-99 Oldsmobile Alero;
2005-99 Pontiac Grand Am
Dorman Part #970-009

If you have an ABS and TRAC OFF light and want to troubleshoot the system, start by examining the connectors at each front wheel bearing. You may find that the entire connector has broken off the bearing is just hanging in mid-air. If the wiring at the sensor appears good, disconnect it. Then disconnect the main connector at the ABS computer (usually located on the driver’s side—just follow the harness back to the computer). With the wiring harness disconnected, use your meter to test each of the wires that go to the ABS sensor. Check for continuity of each wire and then check for a short between the wires. Also check for a short to ground. If you find any of those conditions, replace the harness. Do NOT attempt to fix the short/open. The system operates on such low voltage that the increased resistance of a splice may prevent communication. Also, a splice make actually break again due to the flexing required.

If the harness checks out, your problem is most likely in the ABS sensor wheel bearing/hub assembly. You can test the ABS sensor by connecting a digital multimeter to the ABS sensor connector and setting your meter to AC voltage. Then spin the wheel. You should see AC fluctuations. If you don’t then it’s safe to assume the wiring is broken. If you see fluctuation, you cannot assume that the sensor is good. The multimeter test is not considered the most reliable test. A more accurate test requires a scope.

To replace the wheel bearing/hub, you will need to remove the axle nut. That will require a large socket and a long ½” breaker bar. You can use an impact wrench to remove the axle nut, but you CANNOT use the impact wrench to install the new one. The impact can destroy the new bearing. Also, make sure you install a NEW axle nut. The old one CANNOT be reused. Find the torque value for the new nut and use a torque wrench to set it properly.

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

Hover your mouse over the REPAIR ARTICLES tab at the top of the page. The click on DIAGNOSTICS to search by SYMPTOM, TROUBLE CODE, or read TECH TIPS on how to diagnose a problem

Click on MAKE an MODEL to see all the articles I’ve written for your vehicle
Click on REPAIR TOPICS to read individual articles written for specific automotive systems

If you’ve had your car scanned and know the trouble code go to TROUBLE CODES

Here are some quick links to speed up your research

Click on the link below for speedy navigation:

ABS issues, how to bleed ABS brakes

Airbag issues or SRS light on

Alternator issues or how to test

Belt diagram or serpentine belt issues

Blower motor

Blower motor resistor

Brakes, brake issues, what kind of brake parts to buy, ABS issues

Car Alarms or Antitheft systems

Cooling system, Water pump, What type of coolant to use

Engine flush

Firing order, cylinder layout, finding #1 cylinder

MAF or MAP sensor

Oxygen sensors, How they work, How to change, How to test

PassLock or Passkey

Thermostat issues

Transmission flush

Serpentine belt diagrams

Window issues, power window motor, replace window regulator, glass adhesive

Performance Chip? GM Revokes Warranty on Chipped Vehicles

Rick — Fri, 18 Dec 2009 23:16:46 +0000

GM issued a technical service bulleting (TSB) #09-06-04—026 regarding revocation of warranty coverage on any GM vehicle in which the factory calibrations (software) has been removed or altered. The TSB applies to ALL GM gasoline passenger cars and trucks from 2006- present.

It’s important to note that GM is seeing enough damaged engines and transmissions to make this announcement. Here’s a direct quote from the TSB:

“When alteration to the GM-released engine or transmission control calibrations occurs, it subjects powertrain and driveline components (engine , transmission, transfer case, driveshaft and rear axle) to stresses that were not tested by General Motors. It is because of these unknown stresses, and the potential to alter reliability, durability and emissions performance, that GM has adopted a policy to cancel any remaining warranty coverage to the powertrain and driveline components whenever the presence of a non-GM (aftermarket) calibration is confirmed – even if the non-GM control module calibration is subsequently removed.”

The TSB goes on to instruct the dealers on how to determine if the factory calibrations have been altered or removed. So don’t think you change restore the factory programming and tear into the dealer when they refuse to cover your warranty claim. They CAN tell what you’ve done.

So, if you’re planning on “chipping” your vehicle (which I do NOT recommend), be aware that you’re on your own and that the likelihood of damage to the engine and transmission increases dramatically.

Also, remember this: engine design is always a compromise between power, responsiveness, emissions, and fuel economy. You cannot change one variable without changing all the others. So, while chipping may increase power in one range of operation, you will pay for it in other areas. There’s no free lunch, despite what the chipmakers want you to believe.

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

Hover your mouse over the REPAIR ARTICLES tab at the top of the page. The click on DIAGNOSTICS to search by SYMPTOM, TROUBLE CODE, or read TECH TIPS on how to diagnose a problem

Click on MAKE an MODEL to see all the articles I’ve written for your vehicle
Click on REPAIR TOPICS to read individual articles written for specific automotive systems

If you’ve had your car scanned and know the trouble code go to TROUBLE CODES

Here are some quick links to speed up your research

Click on the link below for speedy navigation:

ABS issues, how to bleed ABS brakes

Airbag issues or SRS light on

Alternator issues or how to test

Belt diagram or serpentine belt issues

Blower motor

Blower motor resistor

Brakes, brake issues, what kind of brake parts to buy, ABS issues

Car Alarms or Antitheft systems

Cooling system, Water pump, What type of coolant to use

Engine flush

Firing order, cylinder layout, finding #1 cylinder

MAF or MAP sensor

Oxygen sensors, How they work, How to change, How to test

PassLock or Passkey

Thermostat issues

Transmission flush

Serpentine belt diagrams

Window issues, power window motor, replace window regulator, glass adhesive

Headlights flicker on vehicle with daytime running lights

Rick — Sun, 06 Dec 2009 18:02:10 +0000

Every manufacturer has their share of problems with daytime running lights. Basically the system senses that the vehicle is running and the headlight switch is off. Programmed conclusion? Must be daylight, otherwise the driver would turn on the headlights. Other systems have light sensors. The Chrysler Daytime Running Light system gets screwed up by corrosion in the intelligent power module. Some GM vehicles fail due to a cracked Daytime Running Light resistor (computer provides power to the headlights, but runs it through a resistor to cut down on the headlamp brightness). Still another GM system runs the headlight commands through Daytime Running Lamp Module located behind the left side of the instrument panel. This module contains a diode that has a high failure rate. The module sends a command to the Daytime Running Lamps Relay located in the convenience center (firewall passenger side).

If you have the latter system, remove the relay and insert a jumper wire across the power terminals. See Relay Layout. If that fixes the problem, replace the relay. If it doesn’t, replace the Daytime Running Lamp Module.

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

Hover your mouse over the REPAIR ARTICLES tab at the top of the page. The click on DIAGNOSTICS to search by SYMPTOM, TROUBLE CODE, or read TECH TIPS on how to diagnose a problem

Click on MAKE an MODEL to see all the articles I’ve written for your vehicle
Click on REPAIR TOPICS to read individual articles written for specific automotive systems

If you’ve had your car scanned and know the trouble code go to TROUBLE CODES

Here are some quick links to speed up your research

Click on the link below for speedy navigation:

ABS issues, how to bleed ABS brakes

Airbag issues or SRS light on

Alternator issues or how to test

Belt diagram or serpentine belt issues

Blower motor

Blower motor resistor

Brakes, brake issues, what kind of brake parts to buy, ABS issues

Car Alarms or Antitheft systems

Cooling system, Water pump, What type of coolant to use

Engine flush

Firing order, cylinder layout, finding #1 cylinder

MAF or MAP sensor

Oxygen sensors, How they work, How to change, How to test

PassLock or Passkey

Thermostat issues

Transmission flush

Serpentine belt diagrams

Window issues, power window motor, replace window regulator, glass adhesive

Anti-Theft Systems for GM Vehicles

Rick — Fri, 29 May 2009 16:33:00 +0000

GM has used a variety of anti-theft systems on their vehicles. When you get a no start, intermittent start, or start then die, you should diagnose the anti-theft system before you start replacing starting components. A tell-tale sign that you’ve got an anti-theft problem is a flashing “Theft” light. Here’s a brief primer on each system and what to look for.

Each GM anti-theft system disables different components. Some disable the engine starter, while others enable the starter but disable fuel injectors. None of them disable spark. So, first understand the difference between vehicle theft deterrent systems.

VAT
The VAT, or vehicle anti-theft was used primarily on 1986-88 Corvettes. The key had a pellet that was married to the vehicle anti-theft module at the factory. If the lock cylinder was turned or bypassed with the proper key installed, the system would disable the starter and kill the injectors. You could NOT perform a system “relearn.”

PassKey I, and II
Similar to the VATS system, these vehicles also used a pellet key. You can identify this system by looking at the key. It has a black resistor pellet with a thin metal edge running along the key. The system enables the starter, but shuts down the injectors after initial startup. So the vehicle would start, then die. This system has a “relearn” feature. It was used on these vehicles

Buick
Century 97-01
Park Avenue 91-96
LeSabre 92-99
Riviera/Reatta 90-01
Regal 94-99
Roadmaster 94-96

Cadillac
Eldorado 89-01
Seville 89-97
Fleetwood 92-96
Deville 90-99
Allante 89-93

Chevrolet
Camero 89-01
Corvette 89-01
Caprice/Impala 94-96
Lumina/Monte Carlo 95-97

Oldsmobile
Cutlass Supreme 94-97
Aurora 95-00
Regency/88 91-99
Toronado 90-93
Pontiac
Firebird 89-01
Grand Prix 94-96
Bonneville 92-99

PassKey III
This system uses a special key (PK3 stamped on the shoulder of the key) with a transponder under the rubber cover. The receiver module is located next to the lock cylinder. When the key is positioned next to the lock cylinder receiver module, it energizes the transponder which sends a coded signal to the receiver. The receiver module checks its memory to see if the signal is correct. If it is, the module sends a signal to the PCM to enable the engine. If the value is valid, the indicator light will remain steady for 2 seconds. You cannot test this system with an ohmmeter. You need a scan tool. If the signal is not correct, the PCM disables the injector and the starter and flashes the light once per second. If an illegitimate key is used or a system problem exists, the light flashes twice per second.

The system is used on:

Buick
Lesabre 2000-on
Park Avenue 97-on

Cadillac
Seville 98-on
Deville 2000-on

Oldsmobile
Aurora 01-on

Pontiac
Bonneville 2000-on

GM Minivans
Venture, Montana, Silhouette

Passlock
This system allows starter operation, then kills the injectors 1-2 seconds after startup. This is a “Hall-Effect” system. The key cylinder housing has a small magnet that rotates past the Passlock sensor. The sensor is powered and detects the rotation. The voltage on the sensor then drops to a specified value (there are 10 different values). There’s no pellet in the key. So basically this system is checking to see that a thief has not popped the lock cylinder to steal the vehicle. you have to perform a Powertrain Control Module (PCM) relearn procedure (need a programming scan tool). The Passlock system was used on:

Buick
Skylark 96-98

Chevrolet
Cavalier 95-on
Impala 2000-on
Malibu 97-on
Monte Carlo 2000-on

Oldsmobile
Achieva 96-on
Cutlass 97-on
Intrigue 98-on

All GM trucks 98-0n

SYSTEM DIAGNOSTICS

PassKey I and II System Diagnostics

There are 15 different key codes. Measure the resistance of the key pellet by connecting an ohmmeter to each side of the key pellet. Once you find the resistance value, remove the lower dash panels and locate two small wires (both white) that run down the base of the steering column. Disconnect the electrical connector where those wires terminate. Then connect an ohmmeter to that electrical connector and insert the key. The reading you get at the end of the two white wires should match the resistance value you got from the key. Next, turn the key. The value on your meter should NOT change or drop out. If it does, you will have to replace the key cylinder. It is COMMON for the wires to break from the key cylinder.

If you have the PassKey system and the engine cranks, runs, and quits AND the THEFT light is on (for about 5 seconds), here are the tests you should perform:

1) Disconnect the electrical connector at the deterrent module. Then turn the ignition switch to RUN while you test the voltage between the dark blue wire in the theft deterrent electrical connector (the one you just disconnected) and a ground point. You should see 5 volts. If you don’t get that voltage, check for an open or short between the dark blue wire and the PCM that supplies the voltage to the module.

If you DO get the 5 volts, turn the ignition off and reconnect the electrical connector. Pierce the insulation on the same wire (with a pin) or back-probe the wire in the connector. Turn the ignition to RUN. The voltage should now read 2.5 volts. If not, replace the theft module. THAT assumes you have already conducted the key pellet test (explained above) and that it passes the test. If you see 2.5 volts and the vehicle still won’t stay running, check the fuel pump relay.

Here’s how it works, The lock cylinder reads the resistance of the pellet in the key and transmits that data to the theft module. Meanwhile, the PCM provides 5 volts on the dark blue wire. When the theft module determines that the proper key has been inserted, it partially grounds the voltage on the dark blue wire. The PCM initially provides fuel injector pulse, but if it doesn’t sees a voltage drop on that dark blue wire, it cuts off the fuel injectors. That’s why you get a crank, start, engine shut down.

So, if the vehicle starts and then dies, AND THE THEFT LIGHT FLASHES, the module is not getting the proper signal from the lock cylinder or the module is bad.

Passlock
Testing this system is similar to the Passkey I and II systems. You want to check the voltage at the bottom of the steering column as you insert the key and rotate it check the yellow signal wire (should be 5 volts before you start the testing). Turn the key.

The value should drop. If it does not, you will have to replace the key cylinder. The “control module” for this system is built into the instrument panel control (IPC) in early years. In later years, the system is controlled by the Body Control Module (BCM), the Electronically Controlled Orifice-steering Assist (EVO), IPC and other systems. If you have to replace the lock cylinder or any of the control modules,

Passkey III

You cannot check this system with an ohmmeter. You will need a scan tool to watch the operation of the system and find the trouble code. Once you get the trouble code, follow the diagnostic procedure based on the specific code.

Some companies make PASSLOCK OVERRIDE SYSTEMS. I don’t have any experience with them. But if you want more information, click HERE

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

Hover your mouse over the REPAIR ARTICLES tab at the top of the page. The click on DIAGNOSTICS to search by SYMPTOM, TROUBLE CODE, or read TECH TIPS on how to diagnose a problem

Click on MAKE an MODEL to see all the articles I’ve written for your vehicle
Click on REPAIR TOPICS to read individual articles written for specific automotive systems

If you’ve had your car scanned and know the trouble code go to TROUBLE CODES

Here are some quick links to speed up your research

Click on the link below for speedy navigation:

ABS issues, how to bleed ABS brakes

Airbag issues or SRS light on

Alternator issues or how to test

Belt diagram or serpentine belt issues

Blower motor

Blower motor resistor

Brakes, brake issues, what kind of brake parts to buy, ABS issues

Car Alarms or Antitheft systems

Cooling system, Water pump, What type of coolant to use

Engine flush

Firing order, cylinder layout, finding #1 cylinder

MAF or MAP sensor

Oxygen sensors, How they work, How to change, How to test

PassLock or Passkey

Thermostat issues

Transmission flush

Serpentine belt diagrams

Window issues, power window motor, replace window regulator, glass adhesive

GM Passlock–Diagnosing and Fixing GM Anti-theft related no-starts

Rick — Tue, 13 May 2008 03:11:00 +0000

The GM Passlock system is fairly simple, especially when compared to other makes. However, if yours is goofing up, you won’t think it’s so simple.

Here’s how it works: When you first turn the key, the PCM provides power to the fuel pump, injectors, and ignition system. You can crank and start the engine. However, there’s a magnet built into the lock cylinder. As you rotate the key, the magnet passes over a Hall Effect sensor—a sensor that detects the presence of a magnetic force. The magnet produces a unique voltage when it passes over the sensor. The sensor sends this voltage signal to the Body Control Module where it is compared to a stored value. If the sent voltage doesn’t match the stored value, the PCM shuts down the fuel injectors for a minimum of 10 minutes and, well, you’re pretty screwed at that point. If you try to start the car again, you will see a blinking Security light. That’s your sign that the Passlock system has shut you down.

What goes wrong: GM vehicles experience a very high failure rate in the lock cylinder and lock housing mechanisms. Fortunately, they’re fairly inexpensive and easy to replace.

Testing the Passlock sytem: Remove the plastic cover shrouds from the steering column near the lock cylinder. Inside you will see the Passkey module surrounding the lock cylinder. It will have 3 wires coming out of it. Turn the key to the ON position and use a DIGITAL multimeter (Do NOT use an analog meter) to backprobe the probe the black and white wires. If you see 12 volts on the white wire and 0 volts on the black wire, you can proceed to the test for the Passkey module. If you do not see those voltage values, you have a wiring problem between the connector and the BCM.

Next, connect your voltmeter to the yellow wire. It should read 5 volts. Keep the probe connected and turn the key to the off position and back to the start position. The Passlock Data Voltage has a potential of 10 different values, ranging from .86 to 4.28 volts. The voltage should drop to a voltage level between those values and stay within .02 volts of the initial reading for at least one minute. Repeat the test several times—you must receive the same voltage for each test. If you do not, replace the lock cylinder and the Passkey housing.

To remove the lock cylinder, first disconnect the negative battery cable and allow the airbag to power down for 5-10 minutes. Slide the Passkey module off the cylinder housing. Insert the key and turn the lock cylinder to the start position. Place a 1/16” allen wrench into the hole on top of the lock module to release the steering column lock cylinder set pin. Then turn the lock cylinder to the RUN position and pull the lock cylinder out. Reverse the procedure to install.

After you replace the cylinder and Passkey module, you will have to conduct a relearn procedure for the BCM to learn the new voltage value. Here’s the procedure: Lock doors and unlock. Clear codes. Turn key and bump starter, leave on for 10 minutes. After a few minutes the dash light will go out. At that point, turn the key to the off position for 90 seconds to 3 minutes. Repeat this procedure 3 times for a total of 30 minutes and on the 4th try the car will start.

Some companies make PASSLOCK OVERRIDE SYSTEMS. I don’t have any experience with them. But if you want more information, click HERE

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

Hover your mouse over the REPAIR ARTICLES tab at the top of the page. The click on DIAGNOSTICS to search by SYMPTOM, TROUBLE CODE, or read TECH TIPS on how to diagnose a problem

Click on MAKE an MODEL to see all the articles I’ve written for your vehicle
Click on REPAIR TOPICS to read individual articles written for specific automotive systems

If you’ve had your car scanned and know the trouble code go to TROUBLE CODES

Here are some quick links to speed up your research

Click on the link below for speedy navigation:

ABS issues, how to bleed ABS brakes

Airbag issues or SRS light on

Alternator issues or how to test

Belt diagram or serpentine belt issues

Blower motor

Blower motor resistor

Brakes, brake issues, what kind of brake parts to buy, ABS issues

Car Alarms or Antitheft systems

Cooling system, Water pump, What type of coolant to use

Engine flush

Firing order, cylinder layout, finding #1 cylinder

MAF or MAP sensor

Oxygen sensors, How they work, How to change, How to test

PassLock or Passkey

Thermostat issues

Transmission flush

Serpentine belt diagrams

Window issues, power window motor, replace window regulator, glass adhesive

No More Radiator Drain Valves in GM vehicles

Rick — Sun, 06 Apr 2008 19:05:00 +0000

Starting in 2003, GM discontinued the use of a drain hose attached to the radiator drain valve. Later, GM discontinued the use of a radiator drain valve altogether. Some models continued to include a drain valve, but the valve was permanently sealed during production. Do NOT try and operate these sealed valves—they will break. GM warns that if you try to remove and replace the valve, debris from the breakage may circulate throughout the system and damage water pump, heater core, and thermostat components.

The bottom line is that you must now either remove the lower radiator hose or use a siphon to remove coolant from the radiator. This bulletin applies to all 1998-04 GM cars and trucks.

Alldatadiy.com

eautorepair.net

Both Alldata and Eautorepair offer professional grade shop manuals at a price you can afford. Check them out!.

Hover your mouse over the REPAIR ARTICLES tab at the top of the page. The click on DIAGNOSTICS to search by SYMPTOM, TROUBLE CODE, or read TECH TIPS on how to diagnose a problem

Click on MAKE an MODEL to see all the articles I’ve written for your vehicle
Click on REPAIR TOPICS to read individual articles written for specific automotive systems

If you’ve had your car scanned and know the trouble code go to TROUBLE CODES

Here are some quick links to speed up your research

Click on the link below for speedy navigation:

ABS issues, how to bleed ABS brakes

Airbag issues or SRS light on

Alternator issues or how to test

Belt diagram or serpentine belt issues

Blower motor

Blower motor resistor

Brakes, brake issues, what kind of brake parts to buy, ABS issues

Car Alarms or Antitheft systems

Cooling system, Water pump, What type of coolant to use