Chart C-1A Electric Load Idle-Up Signal Check

Diagnostic Chart:

Idle-Up Signal Electrical Schematic:

CIRCUIT DESCRIPTION
The ECM receives an idle-up signal at terminal "B3" from the diode module. This signal is present whenever one or more of the following systems is turned "ON."

^ Head lights.
^ Rear window defogger.
^ Stoplights.
^ Heater blower motor.
^ Radiator cooling fan.

The engine rpm will slightly increase for the additional electrical load.

TEST DESCRIPTION
Numbers below refer to the numbers on the diagnostic chart.

1. Checking for electrical load signal to ECM.
2. This is checking for an open circuit to the ECM or a faulty ECM or a faulty diode module.