For 1990-2009 cars

### 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 Descriptors

DTC P0544 03: Exhaust Gas Temperature Sensor 1 Circuit Voltage Below Threshold
DTC P0544 07: Exhaust Gas Temperature Sensor 1 Circuit Voltage Above Threshold
DTC P2031 03: Exhaust Gas Temperature Sensor 2 Circuit Voltage Below Threshold
DTC P2031 07: Exhaust Gas Temperature Sensor 2 Circuit Voltage Above Threshold

### Circuit Description

The exhaust gas temperature (EGT) sensors are variable resistors that measures the temperature of the exhaust gas. The EGT sensor 1 is located in the exhaust pipe after the catalytic convertor. The EGT 2 sensor is located in the exhaust gas particulate filter. The engine control module (ECM) supplies 5 volts to the EGT signal circuit and supplies a ground to the low reference circuit. The EGT sensor temperature information is used by the ECM during the exhaust gas particulate filter cleaning process.

The following table illustrates the difference between temperature, resistance, and voltage:

EGT | EGT Resistance | EGT Signal Voltage
--- | --- | ---
Cold | High | High
Warm | Low | Low

### Conditions for Running the DTC

• | The ignition is ON.

• | The DTCs run continuously when the above condition is met.

### Conditions for Setting the DTC

#### P0544 03 and P2031 03

The ECM detects that the EGT sensor is less than 0.1 volt for greater than 0.5 seconds.

#### P0544 07 and P2033 03

The ECM detects that the EGT sensor is greater than 4.9 volts for greater than 0.5 seconds.

### Action Taken When the DTC Sets

DTCs P0544 and P2031 are Type A DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0544 and P2031 are Type A DTCs.

### Diagnostic Aids

• | After starting the engine, the EGT sensor temperature should rise steadily, then stabilize after the engine reaches operating temperature.

• | If the vehicle has set overnight, the EGT sensor and the IAT sensor values should display within 3°C (5°F).

### 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

1. Engine running, observe the DTC information with a scan tool. DTCs P0544 03, P0544 07, P2031 03, or P2031 07 should not set.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, and the MAIN fuse removed, disconnect the harness connector at the appropriate B131 EGT sensor.
2. Test for less than 5 Ω between the low reference circuit terminal 1 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.

3. Install the MAIN fuse. Ignition ON, verify the scan tool exhaust gas temperature sensor parameter is at 5 V.

⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.

Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.

4. Install a 1 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool exhaust gas temperature sensor parameter is at 0 V.

⇒ | If greater 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 K20 ECM.

5. If all circuits test normal, test or replace the B131 EGT sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Exhaust Temperature Sensor Replacement - Position 1

• | Exhaust Temperature Sensor Replacement - Position 2

• | Control Module References for ECM replacement, setup, and programming

### Repair Verification

Ignition ON, observe the scan tool DPF soot mass parameter. The parameter should be less than 10 grams.

⇒ | If greater than the specified range, perform a DPF service regeneration. Refer to Exhaust Particulate Filter Cleaning.