GMC Cars & Trucks - Recent Questions, Troubleshooting & Support


There is no reset button... Most likely you will need to take it to a dealer for repair or replace the radio

GMC Cars &... | Answered 10 hours ago


Check the plug on the alternator and your fuses. Take a look at these videos. There is also the possibility that the alternator is faulty. You need to test the output current with a voltmeter.

Edited to add, I have just watched this really well presented and informative video on testing alternators. Check the main fuse for the alternator inside your hood fuse box. I would suggest you take a look at the video, even if you don't understand very much of it.

https://www.youtube.com/watch?v=1bK0De9XOP0

https://www.google.com/search?q=1994+GMC+Sonoma+pickup+has+new+alternator+but+won%27t+charge

GMC Cars &... | Answered on Feb 14, 2020


Hi, Mike, the answer to this question is way above my pay grade for this situation, I would call or visit my local dealer or reputable shop's service/parts department and inquire about any possible quick fix, answers, or parts enquiry.
Good luck and have a wonderful day.

GMC Cars &... | Answered on Feb 13, 2020


Mike are you sure it is the blend door? I ask because 99 times out of 100 it is the Blend Door Actuators that go bad. Most all GMC and Chevy are set up the same. Check this out and see if it doesn't help you. Hope this helps you out.
www.youtube.com/watch?v=WiwZeJlAQdo&t=186s

1994 GMC Jimmy | Answered on Feb 12, 2020


That depends on which V-8 you have, a 5.0, 5.7, 6.6?

GMC Cars &... | Answered on Feb 12, 2020


There is a little cable that clips on the part of the steering column that turns when you move the shifting lever and the needle in your gauge so when you move the shifting lever it moves the needle. They rarely break so I would guess yours just came unhooked. It's not easy to see but if you look underneath the sheering column you should be able to see it. If you can't you might need to remove the dash trim around your gauge cluster. Sorry I can't do better than that but it has been years since I changed one. If it is broken you will need a new gauge cluster. I would recommend getting a used one from a junk yard and saving a lot of money. Hope this helps you out.

GMC Cars &... | Answered on Feb 12, 2020


I would recommend changing your temperature sending unit first. Diesel or gas?

GMC Cars &... | Answered on Feb 12, 2020


Start the engine. Aim the timing light at the timing marks on the front of the engine. Turn the distributor to change the timing as needed by grasping the distributor cap and rotating the distributor by hand. Set the timing to 10 degrees and tighten the hold-down bolt and reconnect the timing connector.
Search for: How do you set the timing on a 4.3 Vortec?

GMC Cars &... | Answered on Feb 09, 2020


Why ? You won't fix it , take it to a qualified repair shop before mess it up.This vehicle has a fuel pump driver module (computer) that controls the fuel pump .
Fuel Pump Flow Control Module (FPCM)
The fuel pump flow control module (FPCM) is a serviceable GMLAN module. The FPCM receives the desired fuel pressure message from the engine control module (ECM) and controls the fuel pump located within the fuel tank to achieve the desired fuel pressure. The FPCM sends a 25 KHZ PWM signal to the fuel pump, and pump speed is changed by varying the duty cycle of this signal. Maximum current supplied to the fuel pump is 15 amps. A liquid fuel pressure sensor provides fuel pressure feedback to the FPCM.
Electronic Returnless Fuel System (ERFS)
The electronic returnless fuel system is a microprocessor controlled fuel delivery system which transports fuel from the tank to the fuel rails. It functions as an electronic replacement for a traditional, mechanical fuel pressure regulator. A pressure vent valve within the fuel tank provides an added measure of fuel pump flow control module (FPCM). Desired fuel pressure is commanded by the engine control module (ECM), and transmitted to the FPCM via a GMLAN serial data message. A liquid fuel pressure sensor provides the feedback the FPCM requires for Closed Loop fuel pressure control.

GMC Cars &... | Answered on Feb 07, 2020


Battery hooked up backwards? You may need a new ECM, or you may just need to reset the anti-theft system,

Tip & How-To about Cars & Trucks
Resetting a Vehicle Anti-Theft System
This is how you reset an anti theft system if you have the anti-theft light on, or your car is cranking, but you have no spark.

Doing a full reset of the anti-theft system.

Disconnect both battery leads for at least two hours.
Hold the negative and positive leads together for 5 minutes to fully discharge any power.
Put the key in the ignition, but not turned on. VERY IMPORTANT!
Connect the positive lead.
Connect the negative lead in one swift movement.
Wait 15 minutes for the system to fully reset.
Posted by Andrew... on Jan 14, 2018

GMC Cars &... | Answered on Jan 31, 2020


First off you would need to know how the electronics work on your vehicle , everything works by control modules an the control modules talk an send commands over a serial data network . The power door locks are controlled by the drivers door module DDM .
Door Lock System Components
The power door lock system consists of the following components:
• Driver Door Module (DDM)
• Passenger Door Module (PDM)
• Liftgate Module (LGM)
• Door lock relay
• Door unlock relay
• Body Control Module (BCM)
• Reversible door lock actuators in each of the doors
• LR/RR LOCKS 10A fuse (relay supply voltage)
• Door lock switches in driver and passenger doors (switches are integral components to the DDM and PDM)

A bad or shorting control module could bring down this data network an info like start or anti-theft system messages mite not be getting to the PCM / ECM engine computer .

The power door lock switches are integral components of the DDM and PDM. The switches are two position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDM or PDM. The DDM or PDM monitors these inputs and sends a Class 2 message indicating a change in the switch's respective position. Modules which activate the power door lock motors receive the Class 2 message and activate the motor in the appropriate direction to lock or unlock the vehicle's doors and liftgate. The modules which activate the power lock motors are:
• DDM (driver door lock actuator).
• PDM (passenger front door lock actuator).
• BCM (both rear door lock actuators).
• LGM (liftgate door lock actuator).

Circuit Description (BCM Controlled)
Moving the ignition to the START position signals the body control module (BCM) that engine crank has been requested. The BCM verifies that theft is not active and sends a serial data message to the powertrain control module (PCM) requesting engine start. The BCM also energizes the RUN/CRANK RELAY. When the RUN/CRANK RELAY switch side closes, and the vehicle is in Park or Neutral or with the clutch is fully depressed, if equipped, supplies voltage to the starter relay coil. The PCM verifies the transmission is in Park or Neutral and the clutch is fully depressed, if equipped. The PCM will then ground the control circuit of the starter relay, closing the switch supplying voltage to the starter solenoid. On some vehicles the starter will continue to crank the engine with the key released until it starts of the crank command has timed out to prevent excessive heat build up in the starter circuitry or the PCM receives an engine run flag.

GMC Cars &... | Answered on Jan 29, 2020

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