GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC T-Series Medium Duty Truck F6/F7/F8 🢒 DTC 🢒 DTC P2902

Circuit Description

The exhaust gas recirculation (EGR) valve is driven by the EGR motor and the EGR motor is controlled by the engine control module (ECM). The EGR position sensor generates a signal according to the position of the EGR motor. The EGR valve has the following circuits:

    • The EGR motor U position drive circuit
    • The EGR motor V position drive circuit
    • The EGR motor W position drive circuit
    • A 5-volt reference circuit
    • A low reference circuit
    • The EGR motor U position signal circuit
    • The EGR motor V position signal circuit
    • The EGR motor W position signal circuit

The ECM supplies voltage to the EGR motor on the EGR motor drive circuits. The EGR valve is controlled by the time of voltage supply from the ECM to the EGR motor. When the time of voltage supply increases, the EGR valve position decreases. If the ECM detects the difference between the target EGR position and the actual EGR position is large, this DTC will set.

Conditions for Running the DTC
    • The ignition switch is On.
    • The battery voltage is between 10-16 volts.
    • The engine is running.
    • The deviation of target EGR position is 0.

Conditions for Setting the DTC

The difference between the target EGR position and the actual EGR position is more than the threshold.

Action Taken When the DTC Sets
    • The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.
    • The ECM closes the EGR valve and stops the EGR motor.

Condition for Clearing the DTC
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
    • If an intermittent condition is suspected, the following may cause an intermittent:
       - Poor connections
       - A mis-routed harness
       - Rubbed through wire insulation
       - Broken wire inside the insulation
    • Inspect for the following conditions:
       - Poor connection at ECM--Inspect the harness connectors for the following conditions:
   • Backed-out terminals
   • Improper mating
   • Broken locks
   • Improperly formed or damaged terminals
   • Poor terminal to wire connection
       - Damaged harness--Inspect the wiring harness for damage. If the harness appears to be OK, observe the EGR position or the EGR position sensor display on the scan tool while moving the connectors and the wiring harness related to the sensor. A change in the display will indicate the location of the fault.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Start the engine.
  2. Monitor the DTC information with a scan tool.

Is DTC P2901 also set?

--

Go to DTC P2901

Go to Step 3

3
  1. Test the EGR motor drive circuit between the engine control module (ECM) and the EGR valve for the following conditions:
    2. • An open circuit
    • A short to voltage circuit
    • A short to ground circuit
    • High resistance
  2. Repair the circuits, as necessary.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 4

4

Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement .

Did you complete the replacement?

--

Go to Step 10

--

5
  1. Turn OFF the ignition.
  2. Disconnect the mass air flow (MAF) sensor connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a DMM between the signal voltage circuit of MAF sensor harness and a known good ground.

Is the DMM voltage more than the specified value?

5 V

Go to Step 7

Go to Step 6

6
  1. Test the signal circuit between the ECM and the MAF sensor for a short to voltage circuit.
  2. Repair the circuit, as necessary.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 9

7
  1. Connect the MAF sensor connector.
  2. Observe the Failure Records for this DTC.
  3. Turn OFF the ignition for 30 seconds.
  4. Start the engine.
  5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 8

Go to Diagnostic Aids

8

Replace the MAF sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 10

--

9

Important: The new ECM must be programmed.

Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data .

Did you complete the replacement?

--

Go to Step 10

--

10
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

 

Go to Step 2

Go to Step 11

11

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

 

Go to Diagnostic Trouble Code (DTC) List

System OK