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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls and Fuel - 7.8L (LF8) 🢒 DTC P042E

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P042E: Exhaust Gas Recirculation (EGR) Closed Position Performance

Circuit/System 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.

Conditions for Running the DTC
    • DTCs P0112, P0113, P0117, P0118, P0126, P0403, P0404, P0409, P0652, P0653, P2227, P2228, and P2229 are not set.
    • The battery voltage is between 10-16 volts.
    • The ignition switch is ON for longer than 2 seconds.
    • The engine coolant temperature is between 55-100°C (131-212°F).
    • The intake air temperature is between -7 and +150°C (+19 and +302°F).
    • The barometric pressure is between 80-120 kPa.
    • The absolute value of target EGR change position is less than 0 percent for more than 1 second.

Conditions for Setting the DTC
    • The ECM detects that the EGR learned minimum position is more than 23 percent, and the actual EGR valve position is more than 5 percent for 3 seconds.
        OR
    • The ECM detects that the EGR learned minimum position is less than 7 percent, and the actual EGR valve position is more than 5 percent for 3 seconds.

Action Taken When the DTC Sets

DTC P042E is a Type B DTC.

Conditions for Clearing the DTC

DTC P042E is a Type B DTC.

Diagnostic Aids

Inspect for any recent engine mechanical repairs. An incorrectly installed EGR sensor will cause this DTC to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Verify the integrity of the EGR sensor by inspecting for the following conditions:

    • Damaged components
    • Loose or improper installation

Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

  1. Ignition ON and the EGR valve harness disconnected, measure for 0 volts on the EGR valve position drive circuits.
    2. ⇒If the voltage is more than 0 volts, test the affected motor control circuit for a short to voltage. If the circuits test normal, replace the ECM.
  2. Ignition ON and the EGR valve harness disconnected, probe the EGR valve position drive circuits with a test lamp connected to battery voltage. Verify the test lamp does not illuminate on either circuit.
    3. ⇒If the test lamp illuminates, test the affected motor control circuit for a short to ground. If the circuits test normal, replace the ECM.
  3. Ignition ON and the EGR valve connected, clear all DTCs.
  4. Ignition OFF, allow sufficient time for the control module to power down before disconnecting the EGR valve connector.
  5. Using the peak Min Max function, measure the voltage on the valve position drive circuits as the ignition is turned ON. Voltage should be within 1 volt of the ignition voltage.
    6. ⇒If voltage is less than the specified range, test the valve position drive circuits circuit for high resistance. If the circuit tests normal, replace the ECM.
    ⇒If all circuits test normal, replace the EGR valve.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Exhaust Gas Recirculation Valve Replacement
    •  Control Module References for engine control module (ECM) replacement, setup, and programming