Rick's Free Auto Repair Advice » Bravada

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)

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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.

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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!.

Electronic Fan Clutch Failures on Rainier, Trailblazer, S10, Isuzu Ascender, Oldmobile Bravada, Saab 9-7X, and S15 GMC Envoy

Rick — Tue, 15 Mar 2011 05:16:03 +0000

Electronic Fan Clutch Failures on Rainier, Trailblazer, S10, Isuzu Ascender, Oldmobile Bravada, Saab 9-7X, and S15 GMC Envoy

The electronic fan clutch in the above vehicles experiences almost a 100% failure rate. The purpose of the fan is to reduce drag on the engine at highway speeds where “ram-air” is enough to cool the radiator. At highway speeds, a fully engaged clutch actually spins slower than the air coming through the radiator. So it reduces gas mileage. Thermostatically controlled viscous fan clutches have been around for decades to solve the problem. Those clutches are made from two halves with concentric circles that mesh. The gaps are filled with a silicone fluid. As the engine temperature rises, a thermostatically controlled valve closes off the flow of fluid and the concentric circles lock together under the pressure, transmitting the full torque to the fan blade. However, at higher speeds, the rush of aid past the thermostatic coil opens the valve, allowing the circles to disengage. At that point the fan blade “free-wheels” with the ram air.
Starting in 2002 GM replace the thermostatic coil with an electronically controlled “duty cycle” solenoid and an RPM indicator. The powertrain control module monitors engine and road speed and calculates how fast the fast should turn to properly cool the engine. To adjust fluid pressure in the clutch, the PCM pulses the solenoid on and off in short burst. This is called “duty-cycle.” For example, GM may divide each second into to pulses. If the PCM commands the solenoid on five times every other 1/10 of a second, the fan has a 50% duty cycle. The see how well things are working, the PCM compares the actual fan RPM to the RPM it expected when it calculated duty cycle. If the two speeds don’t match, the PCM makes further adjustments.
When the electronic fan clutches fail, they can lock on full time or free-wheel full time. Free-wheeling causes overheating and lock up reduces gas mileage and causes a howling noise at highway speeds.
To replace the fan clutch you’ll have to remove the fan shroud and fan blade. Mark the orientation of the fan blade before unbolting it completely. It must go back on in the same way. Then unbolt the old electronic fan clutch and swap it out.
The list price on a new fan clutch from the dealer is around $234. But Dorman Products makes an aftermarket replacement for $130. This is a new (not rebuilt part).

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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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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

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.

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

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.

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

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