GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC T-Series Medium Duty Truck F6/F7/F8 🢒 DTC 🢒 DTC P2903

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. The ECM detects the actual EGR valve operation with the mass air flow (MAF) ratio. If the ECM detects an excessively small deviation of the MAF ratio, this DTC will set.

Conditions for Running the DTC
    • DTC P0087, P0088, P0091, P0092, P0107, P0108, P0112, P0113, P0117, P0118, P0182, P0183, P0192, P0193, P0201, P0202, P0203, P0204, P0205, P0206, P0234, P0522, P0523, P0606, P0641, P1087, P1088, P1261, P1263, P1264, P1265, P1266, P2003, P2004, P2007, P2008, P2011, P2012, P2564, P2565, P2900, P2901, P2902, P2903, P2921, P2923 is not set.
    • The ignition switch is ON.
    • The battery voltage is between 10-16 volts.
    • The engine is running.
    • The EGR control is normal.

Conditions for Setting the DTC

The deviation of the MAF ratio when the EGR valve is 20 percent open, and the MAF ratio when the EGR valve is full close is less than 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 control.

Conditions 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.

Test Description

The number below refers to the step number on the diagnostic table.

  1. Operate the vehicle within the same conditions as when the DTC failed. If you cannot duplicate the DTC, using the information included in the Failure Records can help to locate an intermittent condition.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 1

Go to Diagnostic System Check - Engine Controls

2

  1. Observe the Failure Records for this DTC.
  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 3

Go to Intermittent Conditions

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 7

Go to Step 4

4

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

Did you complete the replacement?

--

Go to Step 5

--

5
  1. Observe the Failure Records for this DTC.
  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 6

Go to Step 8

6

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 7

--

7
  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 8

8

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