Diagnostic Aids

Check for any of the following conditions:

• The HIGH ELECTRICAL LOAD parameter on the scan tool can indicate if the PCM has received the rear defogger or parking lights ON signal. The scan tool should indicate Yes when the rear defogger or parking lights are turned ON and engine speed should increase slightly. Check for a malfunction in the IAC system or a short to ground in the Diagnostic Request circuit if the engine speed does not increase.
• A malfunctioning rear defogger or parking light (taillight) circuit may cause erratic electrical load idle-up circuit performance. Check for a properly operating rear defogger or taillight system.
• A PSP switch that does not close, or loss of ground at the PSP switch may cause the engine to stall when the power steering loads are high.
• The scan tool will display A/C Request Signal YES when A/C is selected and the HVAC blower switch is ON at any speed. The scan tool will display A/C CLUTCH ON whenever the PCM is allowing A/C compressor engagement. Therefore the scan tool will also display A/C Clutch ON when any defrost mode is selected.

An intermittent malfunction may be caused by a fault in any one of the idle-up signal circuits. Check the wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.