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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls and Fuel - 7.8L (LG4) 🢒 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 the 3 signals (U, V, W) conditions. If the ECM detects incorrect EGR position sensor signals, this DTC will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2901 Exhaust Gas Recirculation (EGR) Position Sensor Performance

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.

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.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

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. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Perform the actuator test for EGR Solenoid Control with a scan tool.
  4. Inspect the EGR position.

Was a condition found?

Go to Intermittent Conditions

Go to Step 7

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 Programming and Setup, Engine Control Module Replacement/Restore Fuel Rate Data , and Fuel Injector Flow Rate Programming .

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 - Vehicle

System OK