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.
A/C Idle-Up Circuit (1.8L)
A/C compressor control module sends an idle-up signal to PCM when A/C compressor clutch is in operation. PCM compensates for extra engine load by adjusting engine idle speed through IAC valve. See IDLE AIR CONTROL VALVE (1.8L) . PCM then sends A/C compressor control module an A/C cut-out signal to cut operation of A/C compressor clutch. A/C compressor control module will then resume normal cycling of A/C compressor clutch when engine returns to a lighter load. A malfunction in A/C idle-up circuit can set DTC P0505. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article.
Use the Manual With the Right Hardware
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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.