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

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

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

Engine RPM will slightly increase for the additional electrical load.

NOTE: Test numbers refer to numbers on diagnostic chart.

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