The intake air (IA) heater is located in the air inlet tube and is used to warm the incoming air to aid in starting the engine and for proper cylinder combustion. The glow plug control module (GPCM) will command the IA heater ON when the engine coolant temperature is below 40°C (104°F). The power to the IA heater is supplied by the battery positive voltage circuit. The IA heater is connected to the GPCM by the following circuits:

If there is a fault on any of these circuits, a DTC will set.

The digital response signal is high and the command 2 signal is activated.

DTC P0640 is a Type B DTC.

DTC P0640 is a Type B DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ensure that the IA heater Cmd 1 CKT Status parameter displays OK.
2. Ensure that the IA heater can be commanded ON.
3. Engine running, observe the DTC information with a scan tool. DTC P0640 should not set.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

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

1. Disconnect the IA heater
2. Turn ON the ignition. Test the IA heater command 1 circuit terminal 2 for less than 12 volts.

⇒	If greater than 12 volts, test the command 1 circuit for a short to voltage. If the circuit tests normal, replace the glow plug control module.

3. If the command 1 circuit tests normal, replace the IA heater.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.