20 Most Recent 2002 GMC Sierra Questions & Answers


From your description it would seem the towing electrics have been incorrectly wired or perhaps the problem is with your trailer.

My advice is to go back to basics, get yourself a diagram and investigate as deep as necessary. Your car is probably filled with digital electronics including a multiplex lighting system. If the towing electrics are an official GM kit there should be no problems but if it has been wired the old fashioned way a multiway relay should be used to prevent the trailer drawing/interfering with the multiplexed vehicle lights.
That is the safest way but it does mean the circuit becomes more complex.

2002 GMC Sierra | Answered on Sep 16, 2019


How to find a parasitic draw .
Chevrolet Truck Battery Dies Overnight Part
Chevrolet Truck Battery Dies Overnight Part II

On this vehicle it just happened to be the instrument cluster .

2002 GMC Sierra | Answered on Feb 14, 2018


There Is a black or white switch right near the top of the brake pedal lever arm and it is clipped around the pedal arm and attaches to the pivot arm that holds the brake pedal in place.

2002 GMC Sierra | Answered on Jan 24, 2018


You should not see any voltage after the 2-second prime until you actually start cranking the engine. If you don't see power on the grey wire when cranking, try jumpering across the fuel pump relay terminals

2002 GMC Sierra | Answered on Jan 14, 2018


Has nothing to do with the ABS ,wheel speed sensor . You vehicle use's a VSS vehicle speed sensor on the transmission . This VSS is a input to the PCM- engine computer . The PCM sends this info. in a message over the class 2 serial data bus, a communication network for the control modules ,to the instrument cluster . The cluster has a microprocessor with logic programmed in . Having the instrument cluster ,BCM ,an PCM checked for DTC'S - diagnostic trouble code's would be a good step ,plus viewing data to the instrument cluster . Is the PCM sending speed data to the instrument cluster .

Speedometer
The IPC displays the vehicle speed based on the vehicle speed signal from the PCM. The PCM converts the data from the vehicle speed sensor to a 4000 pulses/mile signal. The IPC uses the vehicle speed signal circuit from the PCM in order to calculate the vehicle speed. The speedometer defaults to 0 km/h (0 mph) if a malfunction in the vehicle speed signal circuit exists.

DTC B0540
The DIC receives the vehicle speed information from the PCM. The PCM converts the data from the vehicle speed sensor to a 4000 pulses/mile signal. The PCM also sends a class 2 message to the DIC indicating the vehicle speed. If the DIC determines there is a loss of the vehicle speed signal from the PCM due to a vehicle speed signal circuit malfunction, a DTC sets.
DTC P0608
The PCM creates the vehicle speed output signal by pulsing the circuit to ground. The PCM pulses the circuit at the same rate as the vehicle speed signal input. The PCM monitors the voltage on the vehicle speed output circuit. If the PCM determines the voltage is out of the normal operating range, a DTC sets
DTC P0654
The PCM creates the engine speed output signal by pulsing the circuit to ground at a predetermined hertz rate. The PCM pulses the circuit at the same rate as the engine speed signal input. The PCM monitors the voltage on the engine speed output circuit. If the PCM determines the voltage is out of the normal operating range, a DTC sets.
Speedometer and/or Odometer Inaccurate or Inoperative (Gas)
Install a scan tool.
Raise the vehicle drive wheels. Refer to Lifting and Jacking the Vehicle in General Information.
Start the engine.
Place the transmission into drive for an automatic transmission or third gear for a manual transmission.
With the scan tool, observe the Vehicle Speed parameter in the PCM Engine Data 1 data list.
Does the Vehicle Speed parameter match the speedometer display?

Your best bet , take your vehicle to a qualified repair shop .

2002 GMC Sierra | Answered on Nov 28, 2017


This DTC detects a short to voltage in the Motor Control A or Motor Control B circuits, or a shorted motor.
The transfer case motor is a bi-directional, permanent magnet, D.C. motor. When energized, (through Motor Control A or Motor Control B, the ground is provided by the opposing Motor Control circuit and then grounded through the transfer case shift control module ground circuit), the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between 4H, AUTO 4WD, 2H, N, and 4L ranges. While the transfer case motor is energized the transfer case shift control module also energizes the solenoid for the transfer case lock. The motor lock is disabled (locking action released) and free turning of the transfer case motor and sector shaft is then allowed.

Conditions for Setting the DTC
• The system will test the motor circuits by reading the voltage on each circuit.
• If the system detects a problem with the circuits, the DTC is logged.
• The transfer case shift control module senses a high voltage in the Motor Control A or Motor Control B circuits when a low voltage is expected.
Action Taken When the DTC Sets
• All shifting will be disabled.
• The SERVICE 4WD indicator will be latched on for the remainder of the current ignition cycle.
Conditions for Clearing the DTC
• The transfer case shift control module will clear the DTC if the condition for setting the DTC no longer exists.
• A history DTC will clear after 100 consecutive ignition cycles without a fault present.
• History DTCs can be cleared using a scan tool.

Schematic Reference: Transfer Case Control Schematics
1
Was the Transfer Case Diagnostic System Check performed?
--
Go to Step 2
Go to Diagnostic System Check - Transfer Case
2
Check the transfer Case shift control module for faulty power or grounds. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Was the condition found and corrected?
--
Go to Step 9
Go to Step 3
3
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With the scan tool, command the Motor A/B control ON and OFF.
Does the encoder motor turn ON and OFF?
--
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 4
4
Turn the ignition OFF.
Disconnect the four wire connector at the transfer case.
Turn the ignition ON, with the engine OFF.
Connect a DMM between the Motor Control A circuit harness connector and ground at the transfer case.
Is the voltage reading within the specified value?
0-0.2 V
Go to Step 5
Go to Step 6
5
Connect a DMM between the Motor Control B circuit harness connector and ground at the transfer case.
Is the voltage reading within the specified value?
0-0.2 V
Go to Step 8
Go to Step 7
6
Disconnect the transfer case shift control module.
Test the Motor Control A circuit harness connector for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Was the condition found and corrected?
--
Go to Step 9
Go to Step 8
7
Disconnect the transfer case shift control module.
Test the Motor Control B circuit harness connector for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Was the condition found and corrected?
--
Go to Step 9
Go to Step 8
8
Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .
Is the repair complete?
--
Go to Step 9
--
9
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
--
Go to Step 2
System OK

2002 GMC Sierra | Answered on Jun 16, 2017


If 4x4 is electronic shift, possible decoder motor problem ( common ). The motor is bolted to the t-case and operates the engagement. Have someone operate the shift button while listening to the motor at the t-case. If the motor is ok, you should hear the engagement and the problem will be most likely a vacuum issue to the front diff not allowing the hubs to lock in. If there is no noise heard from the t-case, try tapping on the motor to see if it activates. If it does, suspect an internal motor issue and replacement will be required. Also, check wiring connections to motor for any burned/melted wiring that could indicate a problem

2002 GMC Sierra | Answered on Mar 01, 2016


You need to run a compression check on the cylinders and make sure you don't have a head gasket leak. Sometimes the leak will show up in the oil pan and the oil dipstick will show the truck over filled on oil and other times it will go out the exhaust pipe so that is the reason for the compression check on the cylinders/ Up can buy a gage fairly cheap and then remove each plug and insert the gage the cylinders (while rolling the engine over do not start the engine as you do this, pull the coil wire out.) should all read pretty close to the same if they are ok if not you will find one that is way off from the rest and that is the leaking area. Hope this helps.

2002 GMC Sierra | Answered on Oct 02, 2015


Under the dash is the center is a actuator motor attached to the heat and ac ducts that control where the air is directed be sure it is working, sounds as if it is not, You can replace the motor yourself if it is needed. If memory serves me correctly the motor just screws into the duct work and has an arm on it to move the door. Hope this helps.

2002 GMC Sierra | Answered on Oct 02, 2015


Open up the tailgate by removing the screws on the inside of the door T15 or T20 torx bit is required. Disconnect the latch mechanism by unsnapping the plastic connectors. You should then be able to manually unlatch it. Hope that helps.

2002 GMC Sierra | Answered on Aug 30, 2015


try replacing the oil pressure switch on the back of the block. If IT DOES NOT DETECT OIL PRESSURE IT WILL NOT RUN Kills the fuel pump.

2002 GMC Sierra | Answered on Apr 28, 2015


First off this is really a 2 person job. You need to make sure there are no air bubbles trapped inside the brake lines. Connect a tube to the bleeder valve and submerse the end of that tube under a container of brake fluid.... As you push down on your pedal you should see bubbles coming out of the tube. Keeping pumping on the brake pedal until no more bubbles come out.

https://www.youtube.com/watch?v=lPwM2vn3bT0

2002 GMC Sierra | Answered on Mar 11, 2015


Hi Valeria , If it cranks over your missing spark at the spark plug or your not getting fuel in the engine or the engine has no compression . So you need to test to see what is missing. There are a lot of great videos on youtube. on how to test ! You could try spraying some carburetor cleaner in the engine an see if it try's to start . If it starts you probably have a bad fuel pump. If not check for spark ,an if you have no spark you could have a bad ignition module or bad crankshaft position sensor. What size engine does you vehicle have ? There are three or four different one for your vehicle ! No Start Diagnostic Basics EricTheCarGuy

2002 GMC Sierra | Answered on Mar 06, 2015


need to check your fuel pressure....sounds like a bad fuel pump

2002 GMC Sierra | Answered on Feb 28, 2015


Bad switch in the steering wheel, bad horn relay, bad horn, or a bad connection/wiring issue.

2002 GMC Sierra | Answered on Feb 14, 2015

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