PCM monitors a signal from electric load diode. An electric load will be indicated by either heater blower motor request, rear defogger request or headlight request idle-up signal. PCM will adjust engine idle speed using Idle Speed Control (ISC) motor when an electric load voltage signal is received. When electric load voltage signal is removed, PCM will return engine to normal idle speed. To check electric load idle-up circuit, see TEST C1-1: ELECTRIC LOAD IDLE-UP CIRCUIT CHECK 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 opens throttle plate to control engine speed to prevent rough idle or stalling condition. To check A/C idle-up circuit, see TEST C1-2: A/C IDLE-UP CIRCUIT CHECK 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 TEST C1-3: POWER STEERING PRESSURE (PSP) SWITCH IDLE-UP CIRCUIT CHECK under CIRCUIT TESTS.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Idle-Up Circuit Check

Use the Manual With the Right Hardware

When to See a Mechanic