Electrical Load Idle-Up Signal Diagnosis

Diagnostic Chart:

Schematic:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) receives an electrical load idle-up signal from the diode module. The electrical load idle-up signal is present when one or more of the following systems is turned ON:
^ Headlights
^ The Rear-Window Defogger
^ The Heater Blower Motor

The Idle Air Control (IAC) valve increases the idle air passage opening for the additional electrical load compensation.

DIAGNOSTIC AIDS
A short to ground in the signal circuit between the diode module and the PCM may cause an open in the TAIL fuse.

Check for a faulty electrical connection to the PCM.

An intermittent malfunction may be caused by a fault in the electrical load idle-up circuit. Inspect the wiring harness and the components for any of the following conditions:
^ Backed out terminals
^ Incorrect mating of terminals
^ Broken electrical connector locks
^ Incorrectly formed terminals or damaged terminals
^ Faulty terminal-to-wire connections
^ Physical damage to the wiring harness
^ A broken wire inside the insulation
^ Corrosion of electrical connections, of splices, or of terminals

TEST DESCRIPTION
The numbers below refer to the step numbers in the diagnostic table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks, and to store the applicable freeze frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool stores the information for later reference.
2. This step checks for the electrical load idle-up signal to the PCM.
7. This step checks for each electrical input to the diode module.