Idle-Up Circuit

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PCM monitors a signal from electrical load diode module. An electrical load will be indicated by either heater blower motor request, rear defogger request or headlight/parking light request idle-up signal. PCM will adjust engine idle speed using Idle Speed Control (ISC) motor when an electrical load voltage signal is received. When electrical load voltage signal is removed, PCM will return engine to normal idle speed. To check electrical load idle-up circuit, see ELECTRICAL LOAD IDLE-UP CIRCUIT under CIRCUIT TESTS.

A/C amplifier sends an idle-up signal to PCM when A/C compressor clutch is in operation. PCM will activate Idle Speed Control (ISC) motor. ISC motor opens throttle plate to control engine speed to prevent rough idle or stalling condition. To check A/C idle-up circuit, see A/C IDLE-UP CIRCUIT under CIRCUIT TESTS.

Power Steering Pressure (PSP) switch is located in power steering pump housing. PSP switch signals PCM when vehicle needs power steering assist. When power steering fluid pressure increases, PSP switch will close and signal PCM. PCM will adjust engine idle speed using Idle Speed Control (ISC) motor when PSP switch signal is received. To check power steering pressure idle-up circuit, see POWER STEERING PRESSURE (PSP) SWITCH IDLE-UP CIRCUIT under CIRCUIT TESTS.