TSB : Honda Prelude

Details

NOTE: Shift interlock system is controlled by passenger's multiplex control unit, located behind right kick panel. Ensure Malfunction Indicator Light (MIL) is not illuminated. If MIL is illuminated, diagnose PGM-FI system first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. Turn ignition on. Depress brake pedal. Check if brakelights are on. If brakelights are on, go to next step. If brakelights are not on, repair brakelight circuit. Turn ignition off. Disconnect Transmission Control Module (TCM) harness connectors "A" (26-pin) and "B" (22-pin). TCM is located under carpet on right front footwell, next to ECM. Depress brake pedal. Check voltage between TCM harness connector "B" terminal No. 12 (White/Black wire) and harness connector "A" terminal No. 13 (Brown/Black wire) or No. 26 (Brown/Black wire). If battery voltage is present, go to step 4 . If battery voltage is not present, go to next step. Repair open in circuit between TCM harness connector "B" terminal No. 12 (White/Black wire) and brake switch. See WIRING DIAGRAMS . Reconnect TCM harness connectors "A" and "B". Disconnect passenger's multiplex control unit 20-pin harness connector. Turn ignition on. Depress brake pedal. Check voltage between passenger's multiplex control unit harness connector terminals No. 13 (White/Green wire) and No. 14 (Black wire). See WIRING DIAGRAMS . If battery voltage is present, go to step 6 . If battery voltage is not present, go to next step. Check for open or short in circuit between passenger's multiplex control unit harness connector terminals No. 13 or 14 and TCM harness connector "A" terminal No. 22 (White/Green wire). Repair as necessary. If circuit is okay, check for poor ground or loose TCM connectors. Repair as necessary. If ground or connectors are okay, substitute with a known-good TCM and recheck system. If symptom or problem goes away, replace original TCM. Check voltage between passenger's multiplex control unit harness connector terminals No. 14 (Black wire) and No. 16 (Black/Blue wire). If voltage is present, go to next step. If voltage is not present, go to step 8 . Repair open in circuit between passenger's multiplex control unit harness connector terminal No. 16 (Black/Blue wire) and A/T gear position switch. See WIRING DIAGRAMS Disconnect shift lock solenoid harness connector. Turn ignition on. Check voltage between body ground and shift lock solenoid harness connector terminal No. 1 (Green/Yellow wire). If battery voltage is not present, go to next step. If battery voltage is present, go to step 10 . Check fuse No. 18 (7.5-amp), located in underdash fuse/relay box. Replace fuse as necessary. If fuse is okay, repair open in Yellow/Red wire between shift lock solenoid connector and underdash fuse/relay box. See WIRING DIAGRAMS . Turn ignition off. Check for continuity between passenger's multiplex control unit harness connector terminal No. 15 (Green/Yellow wire) and shift lock solenoid harness connector terminal No. 2 (Green/Yellow wire). If continuity exists, go to next step. If continuity does not exist, repair open in circuit between passenger's multiplex control unit and shift lock solenoid. CAUTION: DO NOT connect battery voltage to shift lock solenoid connector terminal No. 2 (Green/Yellow wire) or diode inside shift lock solenoid will be damaged. Connect battery voltage to shift lock solenoid harness connector terminal No. 1 (Yellow/Red wire). Connect battery ground to shift lock solenoid harness connector terminal No. 2 (Green/Yellow wire). Check shift lock solenoid operation. If shift lock solenoid operates properly, go to next step. If shift lock solenoid does not operate properly, replace shift lock solenoid. Check for loose passenger's multiplex control unit connectors. Repair as necessary. If connectors are okay, substitute with a known-good passenger's multiplex control unit and recheck system. If symptom or problem goes away, replace original passenger's multiplex control unit.