GM Service Manual Online
For 1990-2009 cars only

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 P040B: Exhaust Gas Recirculation (EGR) Temperature Sensor 1 Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open

Short to Voltage

EGR Temperature Sensor 1 or EGR Temperature Sensor 2

P040C or P041C

P040D or P041D

--

Circuit/System Description

The engine control module (ECM) supplies 5 volts to the EGR cooler exhaust gas temperature sensor on the 5-volt reference circuit. The ECM also provides a ground on the low reference circuit. The EGR cooler exhaust gas temperature sensor provides a signal to the ECM on the EGR cooler exhaust gas temperature signal circuit which is relative to the pressure changes in the manifold. The ECM should detect a low signal voltage at a EGR cooler exhaust gas temperature, such as low engine load. The ECM should detect high signal voltage at a high EGR cooler exhaust gas temperature, such as high engine load. The ECM monitors the EGR cooler exhaust gas temperature sensor signal for voltage outside the normal range of the EGR cooler exhaust gas temperature sensor.

Conditions for Running the DTC

    • DTCs P0182, P0183, P0237, P0238, P0409, P040C, P040D, P0506, P0507, P0642, P0643, P0652, P0653, P2228 and P2229 are not set.
    • The following conditions are met for 200 seconds:
       - The battery voltage is between 10-16 volts.
       - The ignition is ON for longer than 2 seconds.
       - The actual EGR position is more than 20 percent.
       - The engine speed is more than 1000 RPM.
       - The fuel temperature is less than 115°C (239°F).
    • The following conditions are met for 10 seconds:
       - The intake throttle position is less than 55 percent.
       - The exhaust brake control is commanded OFF.
       - The DPF status is Not during regeneration.
       - The differential pressure is between -10 and +20 kPa.

Conditions for Setting the DTC

The ECM detects EGR gas temperature error for longer than 10 seconds.

Action Taken When the DTC Sets

DTC P040B is a Type B DTC.

Conditions for Clearing the DTC

DTC P040B 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 OFF, disconnect the harness connector at the EGR gas temperature sensor.
  2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal A and ground.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the control module.
  4. Ignition ON, verify the scan tool EGR gas temperature parameter is more than 950°C (1742°F).
  5. If greater than the specified range, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the control module.
  6. Install a 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool EGR gas temperature parameter is less than 0°C (32°F) .
  7. 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 less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the control module.
    If all circuits test normal, replace the EGR gas temperature sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Exhaust Gas Recirculation Cooler Temperature Sensor Replacement - Position 1
    •  Exhaust Gas Recirculation Cooler Temperature Sensor Replacement - Position 2
    •  Control Module References for engine control module (ECM) replacement, setup, and programming