GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC T-Series Medium Duty Truck F6/F7/F8 🢒 DTC 🢒 DTC P2901

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 signal according to the position of the EGR motor and is sent to the ECM. 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 5 volts to the EGR position sensor on the 5-volt reference circuit. The ECM also provides a ground on the low circuit. The EGR position sensor provides a signal to the ECM on the signal circuits. The ECM decides the EGR valve position according to 3 signals (U, V, W) conditions. If the ECM detects incorrect EGR position sensor signals, this DTC will set.

Conditions for Running the DTC
    • The ignition is On.
    • The battery voltage is between 10-16 volts.

Conditions for Setting the DTC

The EGR motor U, V, and P position signals are all high or low.

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

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. Turn OFF the ignition for 30 seconds.
  2. Monitor the DTC information with a scan tool.

Is DTC P0641 also set?

Go to DTC P0641

Go to Step 3

3
  1. Test the 5-volt reference circuit between the engine control module (ECM) and the exhaust gas recirculation (EGR) valve for an open circuit and a short to ground circuit.
  2. Repair the circuits, as necessary.

Did you find and correct the condition?

Go to Step 10

Go to Step 4

4
  1. Test the signal circuits between the ECM and the EGR valve for the following conditions:
    2. • An open circuit
    • A short to voltage circuit
    • A short to ground circuit
    • A short circuit between the U-side and the V-side, the V-side and the W-side, or the U-side and the W-side
  2. Repair the circuits, as necessary.

Did you find and correct the condition?

Go to Step 10

Go to Step 5

5
  1. Turn OFF the ignition.
  2. Disconnect the EGR valve connector.
  3. Inspect for poor connections at the harness connector of the EGR valve.

Did you find and correct the condition?

Go to Step 10

Go to Step 6

6
  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 7

Go to Diagnostic Aids

7

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

Did you complete the replacement?

Go to Step 8

--

8
  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 9

Go to Step 11

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