Rick's Free Auto Repair Advice » Oldsmobile

ABS light on GM vehicles

Rick — Fri, 16 Apr 2010 17:17:57 +0000

GM has issued a TSB #04-05-025-002A covering the following vehicles:
2004 Buick Rainier
2002-04 Cadillac Escalade, Escalade EXT
2003-04 Chevrolet Silverado
2000-04 Chevrolet Suburban, Tahoe
2003-04 Chevrolet Avalanche, Trailblazer
2003-04 Chevrolet SSR
1999-04 GMC Sierra
2000-04 GMC Yukon, Yukon Denali, Yukon XL
2002-04 GMC Envoy
2004 GMC Envoy XUV
2002-2004 Oldsmobile Bravada

The problem shows up as a glowing ABS light and trouble coded C0265, C0201, U1041 and a loss of communication with the brake module (EBCM). The TSB warns dealers NOT to replace the EBCM. The problem is a bad ground. Refer to a wiring diagram to find the grounding location for your vehicle. Then clean the ground area and spray it with rubberized undercoating.

For midsized utility vehicles, find the location of ground #304
For Chevrolet SSR, find the location for ground #400
For full-size trucks and utilities, find the location for ground #110

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No instrument panel, HVAC controls dead, blower motor dead, flashers dead, GM vehicles

Rick — Sun, 21 Mar 2010 07:36:08 +0000

Bad ground TSB for GM vehicles

GM has issued a TSB #04-08-45-010 covering 2004-05 Buick Rainier, 2002-05 Chevrolet Trailblazer, 2002-05 GMC Envoy, and 2002-03 Oldsmobile Bravada.

The bad ground connection can cause the instrument panel lights to be inoperative, HVAC controls inoperative, blower motor inoperative, radio inoperative, flashers inoperative, and transfer case controls inoperative. The cause has been found to be a poor ground at a splice area G201 located on the right side of the front console area.

To fix the problem, you must remove the center floor console. Then remove the 4 screws that hold the instrument panel lower closeout carpet panel to the instrument panel. Next, remove the panel.

Remove the splice pack bolt. If the bolt is corroded, clean it with a wire brush. Remove any carpet that was trapped during assembly. Clean the ground surface with emery cloth. Reassemble the panel and console.

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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

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.

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.

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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.

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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

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

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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.

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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
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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

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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

Bravada Blazer no heat or little heat

Rick — Thu, 03 Dec 2009 19:51:38 +0000

Readers write to me asking where the heater temperature control valve is on their Chevrolet Blazer and Oldsmobile Bravada. BUT, GM's term for that "valve" is really misleading. It's not a valve at all.

The hot coolant comes into the heater box and into the heater core. The blower motor blows air through the heater core. GM uses a temperature door to regulate how much heat gets into the passenger compartment. Most manufacturers call this a "BLEND" door because it blends hot air from the heater core with outside air to get you the right temperature air.

In this vehicle, that door is opened and closed by an electric actuator motor that sits on top of the heater assembly. That's where all the confusion comes in. GM calls that motor a heater temperature control valve, making you think that it's a plumbing style valve. It's not. It's just an electric motor that opens and closes the blend door.

The other "motors" on the heater assembly are vacuum operated motors that open and close "MODE" doors. They open and close the recirculated air damper, and move the air from the heat/vent/defrost positions.

To test the electric BLEND motor, use a digital multimeter and attach the red probe to the light blue wire at the connector. Connect the black probe to ground. Turn the ignition to RUN and measure voltage at the blue wire as you change the heat setting from hot to cold. The voltage should change from 1 to 12 volts. Then place the red probe on the brown wire. Leave the black probe at ground. You should see battery voltage on this wire. Next, leave the red probe on the brown wire and move the black probe to the black/white wire. You should see battery voltage.

Blazer Bravada heater control wiring diagram

What you've just checked is the varying voltage coming from the control to command the motor to open and close (the blue wire), battery power coming to the motor (the brown wire), and ground (the black/white wire).

If you get those readings, then the control unit is working fine. If you don't, then you either have a broken wire to the brown wire, a bad ground or a problem at the control head.

If all those readings check out, remove the electric motor and move the linkage by hand. If the door opens and closes smoothly, you've got a bad electric motor. If the door binds, you'll have to repair that.

99% of the time, it's a bad electric motor. I'd bet money that the blend door is closed and that's why you're not getting heat.

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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

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Here are some quick links to speed up your research

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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

Key stuck in ignition, GM vehicles

Rick — Mon, 12 Oct 2009 18:59:15 +0000

GM has issued a TSB #05-07-30-021B regarding stuck ignition keys. The TSB applies to 2004-07 Buick Ranier, 2002-08 Chevrolet Trailblazer,, 2002-08 GMC Envoy, and 2003-04 Oldsmobile Bravada.

The most common cause of the problem is the shifter boot caught in the shifter mechanism. Start by inspecting the shifter boot to see if it is caught in the shifter assembly. If it is, reposition the shifter boot. If the boot is damaged, replace it with a new shifter boot. GM warns NOT to replace the entire shifter mechanism. The problem is only with the boot.

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

Remove stuck transfer case fill plugs, GM vehicles

Rick — Mon, 12 Oct 2009 17:56:40 +0000

GM has issued a TSB #99-04-21-001 to discuss methods to remove stuck drain/fill plugs. The TSB applies to 1998-99 Chevrolet and GMC K1-1 Suburban, Utility Models, 1998-99 Oldsmobile Bravada with NOV136 or 246 transfer case.

The drain plugs in these transfer cases are made from aluminum and have a ¼” square drive recess. The user inserts the male end of a standard ¼” square drive extension into the plug to remove it. If too much torque is applied during installation, the threads on the plug may gall and permanently seize, making removal difficult.

If you cannot remove the plug, you must heat the area with a heat gun. As a safety precaution, you MUST clean all oil and grease from the area to prevent a fire. Do NOT use a torch for this procedure. Use only an electric heat gun and follow the procedure below.

1) Apply heat to the case around the plug for 1-2 minutes. Do NOT apply heat directly on the plug itself. Use only enough heat to loosen the plug.

2) If you plan to replace the plug due to thread damage or rounding of the square recess, DO NOT use a steel or brass replacement plug. These metals are dissimilar and will react with the magnesium case, making future removal even MORE difficult.

3) Replacement plugs are available from the dealer. The part number is 15032997.

4) Torque the new plug to 15ft/lbs. That’s NOT a lot of torque, so don’t get carried away here.

Alldatadiy.com

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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

Transfer Case Shudder–TSB fix

Rick — Tue, 25 Aug 2009 04:38:03 +0000

GM has issued a TSB (#99-04-1-005A) for 1999-01 Chevrolet and GMC L-Van models and Oldsmobile Bravada equipped with the NV136 transfer case. The symptom is a vibration or "shudder" that occurs during tight turning on dry pavement and at speeds less than 5mph. The problem has been linked to what GM calls "Slip-stick." That's where the clutch plates in the transfer case bind and then release. The TSB calls for flushing the transfer case fluid with new Auto-TrakII fluid (blue in color). First drain the transfer case fluid (even if the old fluid is blue in color). Refill with new fluid (part #12378508). Then drive the vehicle a minimum of 5 miles until the transfer case fluid is up to operating temperature. Then drain and refill a SECOND time. GM warns that even after performing this flush and fill procedure, it may take up to 100 miles for the problem to disappear. This isn't a recall, so you should expect to pay for this repair.

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.

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