Chart C-1A, Electrical Load Idle-Up Signal Check

ECM receives an idle-up signal from diode module. This signal is present whenever one or more of the following systems is turned or operated.

• Headlights.
• Rear window defogger.
• Brakelights.
• Heater blower motor.
• Radiator cooling fan.

Engine RPM will slightly increase for the additional electrical load.

1. Checks for electrical load signal to ECM.
2. Checks for open circuit to ECM, or faulty ECM or diode module.

Fig 1: Chart C-1A Schematic - Electrical Load Idle-Up Signal Check

Courtesy of GENERAL MOTORS CORP.

Fig 2: Chart C-1A Flow Chart - Electrical Load Idle-Up Signal Check

Courtesy of GENERAL MOTORS CORP.