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 P20E2: Exhaust Gas Temperature (EGT) Sensor 1-2 Correlation
DTC P20E2 5A: Exhaust Gas Temperature (EGT) Sensor 1-2 Plausibility Failure

### Circuit/System Description

The diesel exhaust after-treatment system consists of an under hood pre-catalytic converter and an underbody catalytic converter. The underbody catalytic converter also consists of the main Diesel Oxidation Catalyst (DOC) and the coated Diesel Particulate Filter (DPF). One of the main purposes of the DPF is to collect particulates from the engine exhaust in order to minimize discharge of soot to the atmosphere. The soot particles accumulate in the channels of the DPF and are burned off at regular intervals through a process called regeneration. This prevents the DPF from clogging. The ECM commands the DPF regeneration after calculating various vehicle conditions such as DPF pressure difference, exhaust gas temperature, engine oil quality, engine speed, etc. Excessive accumulation of the soot in the DPF can cause a drop in the engine performance. During regeneration, additional fuel is injected via multiple post injections in order to increase the exhaust gas temperature. During this period, the DPF temperature is raised to approximately 600°C and the accumulated soot is oxidized or burned off into carbon dioxide (CO2).

### Conditions for Running the DTC

• | The ignition is ON, or the engine is running.

• | The DTCs run on a cold start when the above conditions are met.

### Conditions for Setting the DTC

The ECM detects the EGT 1 and EGT 2 sensors are not within a calibrated amount during a cold start-up.

### Action Taken When the DTC Sets

DTC P20E2 is type A DTC.

### Conditions for Clearing the DTC

DTC P20E2 is type A DTC.

### Diagnostic Aids

• | If the engine has sat overnight, both EGT sensors and the ECT sensor values should display within 3°C (5°F).

• | After starting a cold engine, the EGT sensors temperature should rise steadily, then stabilize.

• | High resistance in the circuits of either of the EGT sensors could set a DTC.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

1. Ignition On, observe the diagnostic trouble code (DTC) information with a scan tool. Verify no other DTCs are set.

⇒ | If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

Important: Allow the exhaust to cool completely in order to avoid misdiagnosis.

2. Ignition ON, observe the scan tool EGT sensors and IAT sensor data parameters. Both EGT sensor data parameters, and the IAT sensor data parameter should display within 3°C (5°F).
3. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

### Circuit/System Testing

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

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

3. Install the MAIN fuse. Ignition ON, verify that the scan tool EGT sensor parameter is at 5 volts.

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

Important: 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 1A fused jumper wire between the signal circuit terminal 1 and ground. Verify the scan tool EGT sensor parameter is at 0 volts.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit test normal, replace the ECM.

5. If all circuits/components test normal, replace the 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, programming and setup.

### Repair Verification

Ignition ON, observe the scan tool DPF soot mass parameter. The parameter should be less than 24 grams.

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