Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Idle-Up Circuit (Metro)
PCM monitors a signal from electrical load diode module. An electrical load will be indicated when heater blower motor, rear defogger or headlight/parking lights are turned on. 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 (METRO) under CIRCUIT TESTS.
A/C compressor control module 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 (METRO) under CIRCUIT TESTS.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.