Component Testing GMC Sierra 3500 HD

Component Testing

1. Turn the ignition of and check the motor windings for an internal short to ground inside the motor by probing either the motor A control pin and taking the other lead to ground, or the same can be done using motor B control pin. Motor control A is pin A and motor B control is pin D. If the DMM indicates and short to ground replace the transfer case actuator. If nothing is found continue to the next step.
2. With a DMM check the resistance of the motor windings by probing pin A and pin D on the transfer case actuator. The DMM should indicate 0.3-40 ohms, if it does not replace the transfer case actuator and complete the motor learn procedure. If the actuator is within specifications then replace the transfer case control module, program, and complete the motor learn procedure.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. The ignition is ON.
2. System voltage is 10.5-18 volts.

1. The transfer case shift control module tries to unapply, turn OFF the lock solenoid by grounding the motor control circuit.
2. If the module does not sense the battery voltage at the motor lock control circuit prior to applying the motor lock, the DTC sets.
3. Transfer Case Lock control reads back as a high voltage when a low voltage is expected.

1. All shifting is disabled for failure types 01 and 04, normal shifting can occur for failure types 02 and 08.
2. The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

1. The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
2. A history DTC clears after 40 consecutive warm up cycles without a fault present.
3. History DTCs can be cleared using a scan tool.

When the circuits operating the lock solenoid are not complete the lock is engaged. When the circuit is completed the lock is disengaged.

The battery positive voltage circuit and the lock solenoid control circuit must be tested for opens, shorts to ground, shorts to voltage, and high resistance. This can also result from a electrically faulted solenoid.

1. With the ignition on check which DTC is set. If DTC C0321 is set with failure type byte 04 then do the following. The transfer case lock is unable to hold during a hold test and the transfer case actuator will need to be replaced, and the motor learn procedure performed. If this is not the case continue to the next step.
2. Disconnect the transfer case actuator, turn on the ignition and with a DMM check the battery positive voltage circuit for battery voltage at the transfer case actuator. If battery voltage is not seen then repair the battery positive voltage circuit for an open or high resistance. If the circuit checks out proceed to the next step.
3. Disconnect the transfer case control module connector X2 and check the circuit for an open, high resistance, short to ground, or short to voltage. If condition is found repair the circuit or inline connector 109 as necessary, if the condition is not found refer to «Component Testing»(ref-317202-S30112053052009060900000) .

With the ignition off check the resistance of the lock solenoid with a DMM by probing Pins C and B on the transfer case actuator.

1. If the resistance reads 16-42 ohms then replace the transfer case control module, program, and complete the motor learn procedure. If the resistance is not in range then replace the transfer case actuator, and complete the motor learn procedure.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. The ignition is ON.
2. System voltage is 10.5-18 volts.
3. DTC C0896 is not set.

This DTC sets if one of three components: motor driver inside the transfer case shift control module, transfer case clutch, or the shift motor, exceed the thermal model within the software for the module.

1. All range and mode changes will be disabled while the DTC is current.
2. The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

1. The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
2. A history DTC clears after 40 consecutive warm-up cycles without a fault present.
3. History and current DTCs can be cleared using a scan tool.

The DTC can be set by more than one type of fault. It could be set by faulty wheel speed sensors, a front axle actuator not mechanically engaging, a worn transfer case clutch, or a motor brake not holding properly causing excessive motor engagement.

1. This system compares front wheel speeds to rear wheel speeds to determine if slip is occurring and clutch engagement is necessary to correct this condition if the front axle actuator has not mechanically engaged this slip correction can not happen and the DTC will set. Place the vehicle on a hoist, turn the ignition on, engine off and shift the transfer case to 2WD. With a scan tool command the front axle actuator on using special functions in the scan tool. While one person is holding one of the front tires still, spin the other front tire if the front propshaft turns then the front axle is engaged. If it is engaged go to the next step. If not, tear down and inspect the front axle clutch fork for mechanical binding.
2. Using the scan tool, go into EBCM data display and find the front and rear. Take the vehicle on a short test drive on a level and smooth surface. Compare the front wheel speeds to the rear wheel speeds. If the wheel speeds are erratic or they drop out, this would cause this DTC to set. Consider checking the EBCM for DTCs for the wheel speeds. If the wheel speeds are erratic, use the DTC diagnostics in antilock brakes to diagnose the condition. If this appears normal, to too the next step.
3. The next check will be to see if the motor brake is holding. If it does not, this will cause the motor to stay engaged for extended periods of time causing it to exceed the thermal model. With a scan tool clear the DTC, shift the vehicle to 2WD, and monitor the transfer case motor amperage using the data display. Shift the vehicle to the 4 high mode if the amperage goes up while the motor is shifting and goes back to 0 amps in 5 seconds or less then the brake is holding. If the amperage stays high longer, this indicates the brake is not holding and the actuator will need to be replaced. If the brake holds, go to the next step.
4. Next will be checking the transfer case clutch integrity. Place the vehicle for 4 high and take it for a test drive. Clear the DTC if possible. Monitor front and rear wheel speeds using the EBCM data display. Under heavy acceleration, monitor the front and rear wheel speeds. If the front wheel speeds are much lower, this indicates a weak clutch and a transfer case tear down and inspection will be required. If all of the above check all check out good replace the transfer case shift control module if the DTC continues to set and perform the motor learn procedure/Transfer Case High/Low Clutch Reset.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. The ignition is ON.
2. System voltage is 10.5-18 volts.

1. This DTC sets if the front axle actuator switch shows battery voltage when the actuator is disengaged, or when the front axle actuator shows no voltage when the actuator is engaged.
2. The module also monitors the axle actuator control circuit and sets the DTC if a high voltage is expected (disengaged) and a low voltage is seen. It will also set when a low voltage is expected (engaged) and a high voltage is seen.

1. The front axle may be engaged at all times or disengaged at all time depending on the failure type.
2. The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

1. The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
2. A history DTC clears after 40 consecutive warm up cycles without a fault present.
3. History DTCs can be cleared using a scan tool.

The Ignition 1 voltage circuit and the axle actuator control circuit must be tested for opens, shorts to ground, shorts to voltage, and high resistance. This can also result from a electrically faulted actuator.

1. With the ignition on check which DTC is set. If DTC C0379 is set with failure type byte 08 then do the following. Shift the vehicle into 4 high and look at the scan tool data list to see if the front axle actuator is engaging. If the axle actuator can be heard engaging but the scan tool still indicates disengaged then check the axle switch signal circuit for an open or high resistance. Shift the vehicle to 2 high, if the scan tool indicates the axle actuator is engaged then check the axle switch signal for a short to voltage. If everything checks out go to the next step.
2. Remove the front axle actuator and try to shifting from 4WD to 2WD and see if the states change. If the states change then inspect the front axle for mechanical conditions. Refer to «Four-Wheel Drive Does Not Engage»(ref-317243-S08252148272009060900000) or «Four-Wheel Drive Does Not Disengage»(ref-317243-S05868118352009060900000) . If this checks out then go to the next step.
3. Disconnect the connector at the front axle actuator and check for battery voltage on the ignition 1 circuit. Also check the front axle actuator ground for proper connections. If these circuit test bad repair as necessary checking inline connectors X110 and X109. If these circuits test good go to the next step.
4. Check the axle actuator control circuit for an open, short to ground, or short to voltage. If the actuator control circuit checks good, then short the actuator control circuit to ground at the transfer case control module connector X1 pin 15. This should cause the actuator to engage, remove the ground and then reinstate the ground and the actuator should disengage. If the front axle actuator engages and disengages then replace the transfer case control module, program, and complete the motor learn procedure. If it does not fully engage or disengage then replace the front axle actuator.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. The ignition is ON.
2. System voltage is 10.5-18 volts.

A shift request was received but could not be completed within 15 seconds causing this DTC to set.

1. All shifting is disabled until condition is corrected.
2. The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

1. The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
2. A history DTC clears after 40 consecutive warm up cycles without a fault present.
3. History DTCs can be cleared using a scan tool.

Motor control A shorting to motor control B could cause this DTC.

1. Ignition off with a DMM check to see if motor A control and motor B control are shorted together after disconnecting the transfer case control module and the transfer case actuator. If motor A control is shorted to motor B control repair circuits as necessary. If the circuits checked good go to next step.
2. Remove the transfer actuator and check to see if the shift detent shaft is binding. If the shift lever detent shaft is binding refer to «Transfer Case Disassemble»(ref-317202-S34878150112009060900000) . If the shift lever detent shaft is not binding replace the transfer case actuator.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. The ignition is ON.
2. System voltage is 10.5-18 volts.

1. The transfer case control module sees a PWM (RPS) voltage that does not constantly change but remains high 5 volts or above indicating a short to voltage. Or it may remain low indicating a short to ground 0.5 volts or less.
2. The module does not receive a 5-volt reference of 4.8-5.2 volts.
3. The RPS low reference circuits has an open or high resistance causing a low voltage situation.

1. All shifting is disabled until the condition no longer exists.
2. The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

1. The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
2. A history DTC clears after 40 consecutive warm up cycles without a fault present.
3. History DTCs can be cleared using a scan tool.

A RPS signal voltage that remains low 0.5 or lower indicates a short to ground on the RPS signal voltage circuit. It can also indicate an open or high resistance on the RPS low reference signal circuit.

The RPS 5-volt reference circuit, RPS low reference circuit, and RPS sensor signal circuits should be checked for shorts to ground, shorts to voltage, and opens or high resistance.

1. With the ignition on check the RPS 5-volt reference signal on the RPS connector pin 8 with the connector disconnected using a DMM. The DMM should indicate 4.8-5.2 volts, if the voltage is low check for an open or high resistance or short to ground. If the voltage indicates the voltage is over the specification check for a short to voltage. If the circuit checks good replace the transfer case control module, program, and complete the motor learn procedure. If the circuit checks good with the RPS disconnected, connect the RPS and see if the DTC still show as current. If it does proceed to the next step.
2. With the transfer case shift control module connector X1 and X2 disconnected and the RPS disconnected check the RPS signal circuit and the RPS low reference circuits for shorts to ground, high resistance, or shorts to voltage. If a shorting condition has been found then repair the circuits as necessary. If nothing is found in circuit testing then replace the RPS, and perform the motor learn procedure.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. The ignition is ON.
2. System voltage is 10.5-18 volts.

1. The transfer case control module sees a incremental 8-volt reference signal that is not between 1.5-8.2 volts indicating a short to ground or open if low and a short to voltage if high.
2. The module does not receive a incremental impulse signal voltage between 0.5-4.6 volts.
3. The incremental low reference circuit has an open or high resistance.

1. All shifting is disabled until the condition no longer exists.
2. The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

1. The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
2. A history DTC clears after 40 consecutive warm up cycles without a fault present.
3. History DTCs can be cleared using a scan tool.

An open, high resistance, or short to voltage on the incremental sensor direction signal circuit will cause this DTC to set. If the sensor is determined to be bad the entire transfer case actuator will have to be replaced as the incremental sensor is part of the actuator and can not be replaced independently.

The incremental sensor impulse signal circuit, incremental direction signal circuit, incremental sensor low reference circuit, and the 8-volt reference circuit will need to be check for a short to ground, open, high resistance, and a short to voltage using the following steps.

1. Disconnect the connector at the transfer case actuator and check the 8-volt reference signal on pin G at the transfer case actuator with a DMM, ignition on, the voltage should read 7.8-8.2 volts. If the voltage does not read within the specifications then check the 8-volt reference circuit for a short to voltage, open, high resistance, or short to ground. If the circuit checks good and the voltage is out of range replace the transfer case control module, program, and perform the motor learn procedure. If the circuit checks good continue to next step.
2. At the transfer case actuator, with a jumper harness short the 8-volt reference circuit pin G to the incremental impulse signal pin E and note the voltage on the scan tool data display. If the voltage does not read 7.8-8.2 volts check the incremental impulse signal circuit for and open, high resistance, short to ground, or short to voltage. If the circuit checks good then go to the next step.
3. Check the incremental direction circuit for an open, short to ground, high resistance, or a short to voltage by probing pin F at the transfer case actuator and pin 14 and transfer case control module connector X2. If all circuit test good replace the transfer case actuator and perform the motor learn procedure.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. Ignition ON.
2. System voltage 10.5-18 V.

The transfer case is unable to correct for slip.

1. Shifting is still possible but in a reduced capacity which may cause undesirable slip correction events.
2. The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

1. The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
2. A history DTC clears after 40 consecutive warm up cycles without a fault present.
3. History DTCs can be cleared using a scan tool.

1. Verify that DTC C0306 in not set. If the specified DTC is set diagnose that first.
2. Verify that no EBCM wheel speed sensor DTCs are set. If the specified DTC is set diagnose that first.
3. If no other DTCs are found then refer to «Transfer Case Disassemble»(ref-317202-S34878150112009060900000) in order to inspect for possible clutch damage.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. The ignition is ON.
2. System voltage is 10.5-18 volts.

Both sensors must be showing a valid position at the time the DTC is set.

1. Shifting is still disabled until the DTC has cleared itself.
2. The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

1. The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
2. A history DTC clears after 40 consecutive warm up cycles without a fault present.
3. History DTCs can be cleared using a scan tool.

Each of the two sensors show the transfer case movement in degrees. Find the sensor either the incremental sensor or the RPS that seems to not be showing a reading in degrees and is doing so erratically this is probably the sensor causing the DTC.

Inspect the RPS sensor for damage at the mating surface with the rotational position shaft.

1. If the RPS sensor shows damage at the mating surface then replace the RPS sensor. If no damage is found attempt to turn the shaft while the transfer case in stationary in one mode.
2. If the shaft can be turned then internal damage has occurred to this shaft, refer to transfer case disassemble and inspection and repair as necessary. If no damage is found and the RPS sensor seems to show a steady degrees rotation reading on the scan tool data list then replace the transfer case two/four wheel drive actuator.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. The ignition is ON.
2. System voltage is 10.5-18 volts.

The EEPROM, RAM and ROM, and ECM Microprocessor do self checks against one another and the data does not match causing the DTC to set.

1. Shifting is still disabled until the DTC has cleared itself.
2. The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

1. The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
2. A history DTC clears after 40 consecutive warm up cycles without a fault present.
3. History DTCs can be cleared using a scan tool.

It is sometimes possible to set this DTC falsely due to low voltage. Attempt to clear this DTC and retest.

If this DTC sets attempt to clear the DTC and Retest.

1. If the DTC is cleared, but then resets then replace the transfer case control module, program, and complete the transfer case motor learn procedure.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. Ignition ON.
2. System voltage 10.5-18 V.

The motor learn procedure for a new TCCM has not been performed.

1. Shifting is still disabled until the motor learn procedure has been performed.
2. The SERVICE 4WD indicator does not light for this DTC.

The TCCM clears the DTC once the motor learn procedure has been successfully performed.

Perform the motor learn procedure.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. The ignition is ON.
2. System voltage is 10.5-18.5 volts.

The voltage is above 18.5 volts or below 10.5 volts for 15 seconds.

1. Shifting is disabled until the voltages change to be within the specifications.
2. The SERVICE 4WD will illuminate for the remainder for the ignition cycle.

1. The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
2. A history DTC clears after 40 consecutive warm up cycles without a fault present.
3. History DTCs can be cleared using a scan tool.

Perform the motor learn procedure before normal operation will occur.

1. If the voltage is low check the voltage on other vehicle systems to determine if this is a vehicle wide condition and take appropriate actions. If this is transfer case specific check the ignition 3 feed to the transfer case control module and the ground for the transfer case control module for proper connections.
2. If the voltage is high, this is likely a vehicle issue such as an alternator problem or the vehicle has been hooked up improperly during a jump start.
3. After the condition is corrected perform the motor learn procedure.

1. Perform the «Diagnostic System Check - Vehicle»(ref-317170-S03444519162009060900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-317170-S02898624092009060900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-317170-S23773585642009060900000) provides an overview of each diagnostic category.

1. Measure the resistance between the VSS high signal circuit and the VSS low signal circuit. The resistance should be between 1,420-2,140 ohms. If the value is greater than 2,140 ohms, test the VSS high signal circuit and the VSS low signal circuit for an open. If the value is less than 1,420 ohms, test the VSS high signal and the VSS low signal circuits for a shorted together condition.
2. Measure the resistance of the VSS high signal circuit to ground. The resistance should be greater than 10M ohms. If the value is less than 10M ohms, repair the short to ground.
3. Measure the resistance between the VSS low signal circuit and ground. The resistance should be greater than 10M ohms. If the value is less than 10M ohms, repair the short to ground.
4. Reconnect the ECM connector. Disconnect the VSS connector. Ignition ON, test the VSS high signal circuit for a short to voltage. If all circuits/connections test normal, test or replace the VSS.
5. If all previous steps for circuit checking and VSS replacement have been made and all component testing has been performed and the condition persists replace the ECM.

1. Verify the VSS resistance is within the specified range.
2. Using a terminal test kit, connect the DMM between the VSS high signal and the VSS low signal circuits at the VSS connector. Raise and support the drive wheels. While rotating the drive wheels by hand ensure the AC voltage reading on the DMM is above 0.4 volt. If the AC voltage is not above 0.4 volt, replace the VSS.