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.
2001 Honda Prelude Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Air Conditioning Signal Circuit: Prelude
- Turn ignition off. Disconnect A/C pressure switch and A/C diode connectors. See A/C SIGNAL COMPONENT LOCATIONS table. Turn ignition on. Backprobing, measure voltage between PCM connector "A" (32-pin connector) terminal No. 9 (Brown/Black wire) and PCM connector "C" (31-pin connector) terminal No. 5 (Blue/Orange wire). See Figure and Figure . If battery voltage does not exist, go to next step. If battery voltage does exist, go to step 3.
- Turn ignition switch off. Disconnect PCM connector "C" (31-pin connector). Check continuity of Blue/Orange wire between body ground and PCM connector "C" (31-pin connector) terminal No. 5. If continuity exists, repair short in Blue/Orange wire between A/C pressure switch and PCM connectors. See WIRING DIAGRAMS article. If continuity does not exist, substitute a known-good PCM and retest. See SUBSTITUTING POWERTRAIN CONTROL MODULE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - PRELUDE article. If symptom or indication goes away, replace original PCM. If symptom or indication does not go away, inspect A/C system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
- Turn ignition off. Reconnect A/C pressure switch and A/C diode connectors. Turn ignition on. Backprobing, momentarily connect a fused jumper wire between PCM connector "A" (32-pin connector) terminals No. 9 (Brown/Black wire) and No. 17 (Pink/Blue wire), several times. If A/C compressor clutch does not make a clicking sound, go to next step. If A/C compressor clutch makes a clicking sound, go to step 5.
- Backprobing, momentarily connect a jumper wire between body ground and A/C compressor clutch relay connector terminal No. 4 (Pink/Blue wire), several times. See Fig 1. See A/C SIGNAL COMPONENT LOCATIONS table. If A/C compressor clutch makes a clicking sound, repair open in Pink/Blue wire between A/C compressor clutch relay and PCM connectors. See WIRING DIAGRAMS article. If A/C compressor clutch does not make a clicking sound, inspect A/C system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
- Start engine. Turn A/C and blower motor switches on. If A/C does not operate, go to next step. If A/C operates, A/C signal is okay.
- Backprobing, measure voltage between PCM connector "A" (32-pin connector) terminal No. 9 (Brown/Black wire) and PCM connector "C" (31-pin connector) terminal No. 5 (Blue/Orange wire). See Figure and Figure . If voltage reading is not less than one volt, repair open in Blue/Orange wire between A/C pressure switch and PCM connectors. See WIRING DIAGRAMS article. If voltage reading is less than one volt, substitute a known-good PCM and retest. See SUBSTITUTING POWERTRAIN CONTROL MODULE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - PRELUDE article. If symptom or indication goes away, replace original PCM. If symptom or indication does not go away, inspect A/C system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
Factory Service Tools
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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.