Home ReviewsRefund
Home/Honda/Accord/Honda Accord VI (1997-2002)/Repair manual/Testing & Diagnostics/Idle Control System: Diagnosis
Contents Wiring diagrams Section: Testing & Diagnostics All sections

Idle Control System: Diagnosis Honda Accord VI

Testing & Diagnostics 21 illustrations ~1736 words

DTC Troubleshooting

DTCDescription
DTC P0505Idle Control System Malfunction
DTC P1519IAC Valve Circuit Malfunction

DTC Troubleshooting Index

Note. If DTC P1519 is stored at the same time as DTC P0505, troubleshoot DTC P1519 first, then recheck for DTC P0505.

Scheme 62

Scheme 62: DTC P0505: Idle Control System Malfunction
Scheme 62: DTC P0505: Idle Control System Malfunction
  1. Start the engine. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on, then let it idle.
  2. Check the engine speed at idle under no-load conditions: headlights, blower fan, rear defogger, radiator fan, and air conditioner off. Is it 700 +/- 50 rpm? YES - Intermittent failure, system is OK at this time. NO - If the idle speed is less than 650 rpm, go to step 3; if it's 750 rpm or higher, go to step 4 .
  3. Disconnect the 3P connector from the IAC valve. Does the engine speed increase or fluctuate? YES - Adjust the (base) idle speed (see «Idle Speed Adjustment»(ref-178023-S30714917212005060900000) ). If it's impossible, clean the ports in the throttle body. NO - Replace the IAC valve.
  4. Turn the ignition switch OFF.
  5. Remove the intake air duct from the throttle body.
  6. Start the engine and let it idle.
  7. Put your finger on the lower port (A) in the throttle body. Does the engine speed drop? YES - Adjust the idle speed (see «Idle Speed Adjustment»(ref-178023-S30714917212005060900000) ). If it's impossible, replace the IAC valve. NO - Check for vacuum leaks, make sure the throttle valve is completely closed, and repair as necessary.

Scheme 63

Scheme 63: DTC P1519: IAC Valve Circuit Malfunction
Scheme 63: DTC P1519: IAC Valve Circuit Malfunction

Scheme 64

Scheme 64
Scheme 64

Scheme 65

Scheme 65
Scheme 65

Scheme 66

Scheme 66
Scheme 66

Scheme 67

Scheme 67
Scheme 67

Scheme 68

Scheme 68
Scheme 68
  1. Reset the ECM/PCM (see «HOW TO RESET THE ECM/PCM»(ref-177983-S09317242002005060900000) ).
  2. Turn the ignition switch ON (II). Is DTC P1519 indicated? YES - Go to step 3. NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the IAC valve and the ECM/PCM.
  3. Turn the ignition switch OFF.
  4. Disconnect the IAC valve 3P connector.
  5. Turn the ignition switch ON (II).
  6. At the wire harness, measure voltage between IAC valve 3P connector terminal No. 2 and body ground. Is there battery voltage? YES - Go to step 7. NO - Repair open in the wire between the IAC valve and the PGM-FI main relay.
  7. Turn the ignition switch OFF.
  8. Check for continuity between body ground and IAC valve 3P connector terminal No. 1. Is there continuity? YES - Go to step 9. NO - Repair open in the wire between the IAC valve and G101.
  9. Disconnect ECM/PCM connector B (25P).
  10. Check for continuity between body ground and ECM/PCM connector terminal B23. Is there continuity? YES - Repair short in the wire between the IAC valve and the ECM/PCM (B23). NO - Go to step 11.
  11. Connect IAC valve 3P connector terminal No. 3 to body ground with a jumper wire.
  12. Check for continuity between ECM/PCM connector terminal B23 and body ground. Is there continuity? YES - Go to step 13. NO - Repair open in the wire between the IAC valve and the ECM/PCM (B23).
  13. Reconnect the IAC valve 3P connector.
  14. Turn the ignition switch ON (II).
  15. Measure voltage between body ground and ECM/PCM connector terminal B23. Is there battery voltage? YES - Substitute a known-good ECM/PCM and recheck (see «HOW TO SUBSTITUTE THE ECM/PCM FOR TESTING PURPOSES»(ref-177983-S06033682252005060900000) ). If the symptom/indication goes away, replace the original ECM/PCM. NO - Replace the IAC valve.

Scheme 69

Scheme 69: A/C Signal Circuit Troubleshooting
Scheme 69: A/C Signal Circuit Troubleshooting

Scheme 70

Scheme 70
Scheme 70

Scheme 71

Scheme 71
Scheme 71

Scheme 72

Scheme 72
Scheme 72
  1. Turn the ignition switch OFF.
  2. Disconnect the A/C pressure switch connector.
  3. Turn the ignition switch ON (II).
  4. Measure voltage between ECM/PCM connector terminals A27 and B20. Is there approx. 5V? YES - Go to step 5. NO - Go to step 12 .
  5. Turn the ignition switch OFF.
  6. Reconnect the A/C pressure switch connector.
  7. Turn the ignition switch ON (II).
  8. Momentarily connect ECM/PCM connector terminals A17 and B20 with a jumper wire several times. Is there a clicking noise from the A/C compressor clutch? YES - Go to step 9. NO - Go to step 15 .
  9. Start the engine.
  10. Turn the blower switch ON.
  11. Turn the A/C switch ON. Does the A/C operate? YES - The air conditioning signal is OK. NO - Go to step 16 .
  12. Turn the ignition switch OFF.
  13. Disconnect ECM/PCM connector A (32P)
  14. Check for continuity between body ground and ECM/PCM connector terminal A27. Is there continuity? YES - Repair short in the wire between the ECM/PCM (A27) and the A/C pressure switch. NO - Substitute a known-good ECM/PCM and recheck (see «HOW TO SUBSTITUTE THE ECM/PCM FOR TESTING PURPOSES»(ref-177983-S06033682252005060900000) ). If the prescribed voltage is now available, replace the original ECM/PCM. If not, check the A/C system for other symptoms.
  15. Momentarily connect under-hood fuse/relay box 16P connector terminal No. 11 to body ground with a jumper wire several times. Is there a clicking noise from the A/C compressor clutch? YES - Repair open in the wire between the ECM/PCM (A17) and the A/C clutch relay. NO - Check the A/C system for other symptoms.
  16. Measure voltage between ECM/PCM connector terminals A27 and B20. Is there less than 1.0 V? YES - Substitute a known-good ECM/PCM and recheck (see «HOW TO SUBSTITUTE THE ECM/PCM FOR TESTING PURPOSES»(ref-177983-S06033682252005060900000) ). If the symptom/indication goes away, replace the original ECM/PCM. If not, inspect the air conditioning system. NO - Repair open in the wire between the ECM/PCM (A27) and the A/C pressure switch.

Scheme 73

Scheme 73: Alternator FR Signal Circuit Troubleshooting
Scheme 73: Alternator FR Signal Circuit Troubleshooting

Scheme 74

Scheme 74
Scheme 74

Scheme 75

Scheme 75
Scheme 75

Scheme 76

Scheme 76
Scheme 76
  1. Disconnect the 4P connector from the alternator.
  2. Turn the ignition switch ON (II).
  3. Measure voltage between ECM/PCM connector terminals B20 and C5. Is there approx. 5V? YES - Go to step 4. NO - Go to step 14 .
  4. Turn the ignition switch OFF.
  5. Reconnect the alternator 4P connector.
  6. Start the engine. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on, then let it idle.
  7. Measure voltage between ECM/PCM connector terminals B20 and C5. Does the voltage decrease when the headlights and rear window defogger are turned on? YES - The ALT FR signal is OK. NO - Go to step 8.
  8. Turn the ignition switch OFF.
  9. Disconnect the negative cable from the battery.
  10. Disconnect ECM/PCM connector C (31P).
  11. Disconnect the ALT 4P connector.
  12. Connect the alternator 4P connector terminal No. 4 to body ground with a jumper wire.
  13. Check for continuity between body ground and ECM/PCM connector terminal C5. Is there continuity? YES - Troubleshoot the charging circuit (see «GENERATORS & REGULATORS»(ref-138691) ). NO - Repair open in the wire between the ECM/PCM (C5) and the alternator.
  14. Turn the ignition switch OFF.
  15. Disconnect the negative cable from the battery.
  16. Disconnect ECM/PCM connector C (31P).
  17. Check for continuity between body ground and ECM/PCM connector terminal C5. Is there continuity? YES - Repair short in the wire between the ECM/PCM (C5) and the alternator. NO - Substitute a known-good ECM/PCM and recheck (see «HOW TO SUBSTITUTE THE ECM/PCM FOR TESTING PURPOSES»(ref-177983-S06033682252005060900000) ). If the prescribed voltage is now available, replace the original ECM/PCM.

Starter Switch Signal Circuit Troubleshooting

Note. M/T: Clutch pedal be pressed A/T: Transmission in Park or neutral

Scheme 77

Scheme 77: Starter Switch Signal Circuit Troubleshooting
Scheme 77: Starter Switch Signal Circuit Troubleshooting
  1. Measure voltage between ECM/PCM connector terminals A24 and B20 with the ignition switch in the start position (III). Is there battery voltage? YES - The starter switch signal is OK. NO - Go to step 2.
  2. Inspect the No. 13 STARTER SIGNAL (7.5 A) fuse in the driver's under-dash fuse/relay box. Is the fuse OK? YES - Repair open in the wire between the ECM/PCM (A24) and the No. 13 STARTER SIGNAL (7.5 A) fuse. NO - Repair short in the wire between the ECM/PCM (A24) and the No. 13 STARTER SIGNAL (7.5 A) fuse or the PGM-FI main relay. Replace the No. 13 STARTER SIGNAL (7.5 A) fuse.

Scheme 78

Scheme 78: PSP Switch Signal Circuit Troubleshooting
Scheme 78: PSP Switch Signal Circuit Troubleshooting

Scheme 79

Scheme 79
Scheme 79

Scheme 80

Scheme 80
Scheme 80

Scheme 81

Scheme 81
Scheme 81
  1. Turn the ignition switch ON (II).
  2. Measure voltage between ECM/PCM connector terminals A26 and B20. Is there less than 1.0 V? YES - Go to step 3. NO - Go to step 6 .
  3. Start the engine.
  4. Turn the steering wheel to full lock position.
  5. Measure voltage between ECM/PCM connector terminals A26 and B20. Is there battery voltage? YES - The PSP switch signal is OK. NO - Go to step 11 .
  6. Turn the ignition switch OFF.
  7. Disconnect the PSP switch 2P connector.
  8. Turn the ignition switch ON (II).
  9. At the harness side, connect PSP switch 2P connector terminals No. 1 and No. 2 with a jumper wire.
  10. Measure voltage between ECM/PCM connector terminals A26 and B20. Is there less than 1.0 V? YES - Replace the PSP switch. NO - Check for an open in the wire between the ECM/PCM (A26) and the PSP switch, or an open in wire between the PSP switch and G302.
  11. Turn the ignition switch OFF.
  12. Disconnect the PSP switch 2P connector.
  13. Turn the ignition switch ON (II).
  14. Measure voltage between ECM/PCM connector terminals A26 and B20. Is there battery voltage? YES - Replace the PSP switch. NO - Go to step 15.
  15. Turn the ignition switch OFF.
  16. Disconnect ECM/PCM connector A (32P).
  17. Check for continuity between body ground and ECM/PCM connector terminal A26. Is there continuity? YES - Repair short in the wire between the ECM/PCM (A26) and the PSP switch. NO - Substitute a known-good ECM/PCM and recheck (see «HOW TO SUBSTITUTE THE ECM/PCM FOR TESTING PURPOSES»(ref-177983-S06033682252005060900000) ). If the prescribed voltage is now available, replace the original ECM/PCM.

Scheme 82

Scheme 82: Brake Pedal Position Switch Signal Circuit Troubleshooting
Scheme 82: Brake Pedal Position Switch Signal Circuit Troubleshooting
  1. Check the brake lights. Are the brake lights on without pressing the brake pedal? YES - Inspect the brake pedal position switch (see Brake Pedal & Brake Pedal Position Switch Adjustment ). NO - Go to step 2.
  2. Press the brake pedal. Do the brake lights come on? YES - Go to step 3. NO - Go to step 4 .
  3. Measure voltage between ECM/PCM connector terminals A32 and B20 with the brake pedal pressed. Is there battery voltage? YES - The brake pedal position switch signal is OK. NO - Repair open in the wire between the ECM/PCM (A32) and the brake pedal position switch.
  4. Inspect the STOP (20A) fuse in the under-hood fuse/relay box. Is the fuse OK? YES - Repair open in the wire between the brake pedal position switch and the STOP (20 A) fuse. Inspect the brake pedal position switch (see Brake Pedal & Brake Pedal Position Switch Adjustment ). NO - Repair short in the wire between the ECM/PCM (A32) and the STOP (20A) fuse. Replace the STOP (20A) fuse.

More articles — Idle Control System