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 whenever one or more of the following systems is turned ON (operating):
^ Headlights
^ Rear Window Defogger
^ Heater Blower Motor

The Idle Speed Control (ISC) motor increases the throttle valve opening in order to compensate for the additional electrical load.

DIAGNOSTIC AIDS
A short to ground of the BRN/YEL wire 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 components for any of the following conditions:
^ Backed out terminals
^ Improper mating of terminals
^ Broken electrical connector locks
^ Improperly formed or damaged terminals
^ Faulty terminal to wire connections
^ Physical damage to the wiring harness
^ A broken wire inside the insulation
^ Corrosion of electrical connections, splices, or 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 store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool 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.