P0640

DTC P0640

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0640
- Intake Air Heater Control Circuit

Diagnostic Fault Information






Circuit/System Description

The intake air heater (IAH) is located at the intake manifold outlet and is used to heat the air before it enters the inner cooler during cold engine operation. The engine control module (ECM) determines when to request the glow plug control module to turn ON and OFF the intake air heater. The glow plug control module controls the intake air heater current by monitoring the feedback circuits of the intake air heater. The intake air heater will only be commanded ON while the engine is running if required by the ECM.

Conditions for Running the DTC

* The Intake Air Heater is commanded OFF.

* DTC P0640 runs continuously when the above condition is met.

Conditions for Setting the DTC

The glow plug control module detects voltage on the Intake Air Heater Switch On/Off Signal circuit for greater than 2 s when the intake air heater is commanded OFF.

Action Taken When the DTC Sets

DTC P0640 is a Type B DTC.

Conditions for Clearing the DTC

DTC P0640 is a Type B DTC.

Reference Information

Schematic Reference

Engine Controls Schematics [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)

Description and Operation

Intake Air Heater System Description Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Verify the scan tool IAH Command 1 Ckt. Status parameter displays OK.

• If scan tool does not display OK
Refer to Circuit/System Testing.

• If scan tool displays OK

2. Verify the Intake Air Heater can be commanded ON with the scan tool.

• If IAH cannot be commanded ON
Refer to Circuit/System Testing.

• If IAH can be commanded ON

3. 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.

• If DTC resets
Refer to Circuit/System Testing.

• If DTC does not reset

4. All OK.

Circuit/System Testing

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

1. Ignition OFF.

2. Disconnect the harness connector at the E24 Intake Air Heater.

3. Ignition ON.

4. Test for less than 2 V between the Intake Air Heater Switch On/Off Signal circuit terminal 2 and ground.

• If greater than 2 V
Test the Intake Air Heater Switch On/Off Signal circuit for a short to voltage. If the circuit tests normal, replace the K34 glow plug control module.

• If less than 2 v

5. Replace the E24 Intake Air Heater.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Intake Air Heater Replacement Service and Repair

* Control Module References Control Module References for glow plug control module replacement, programming, and setup.