Idle Control System: Diagnosis Honda S2000 AP1

DTC Troubleshooting

DTC INDEX

Note. If DTC P1519 is stored at the same time as DTC P0505, troubleshooting DTC P1519 first, then recheck for DTC P0505. Before you troubleshoot, record all freeze data and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).

Scheme 147

1. Start the engine. Hold the engine speed at 3,000 RPM without load (in neutral) until the radiator fan comes on, then let it idle.
2. Check the engine speed at idle without load conditions: headlights, blower fan, radiator fan, and air conditioner off. Is the idle speed 800 +/- 50 RPM? YES - Intermittent failure, system is OK at this time. NO - If the idle speed is less than 750 RPM, go to step 3; if it is 850 RPM or higher, go to step 4.
3. Disconnect the idle air control (IAC) valve 3P connector. Dose the engine speed increase or fluctuate? YES - Check the idle speed with a different load condition (electrical, A/C, etc.). If it is out of specification, replace the IAC valve (see «SPECIAL TOOLS»(ref-221324-S23506078702006022400000) ). NO - Replace the IAC valve (see «SPECIAL TOOLS»(ref-221324-S23506078702006022400000) ).
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 fingers on the upper and lower ports (A) in the throttle body. Does the engine speed drop below 750 RPM? YES - Check the idle speed with a different load condition (electrical, A/C, etc.). If it is out of specification, replace the IAC valve (see «SPECIAL TOOLS»(ref-221324-S23506078702006022400000) ). NO - Check for vacuum leaks at these parts: PCV valve PCV hose EVAP canister purge valve Intake manifold Throttle body Brake booster hose

Note. If DTC P0511 is stored at the same time as DTC P0506, troubleshooting DTC P0511 first, then recheck for DTC P0506. Before you troubleshoot, record all freeze data and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).

1. Start the engine. Hold the engine speed at 3,000 RPM without load (in neutral) until the radiator fan comes on, then let it idle.
2. Check the engine speed at idle without load conditions: headlights, blower fan, radiator fan, and air conditioner off. Is the idle speed 800 +/- 50 RPM? YES - Intermittent failure, system is OK at this time. NO - Go to step 3.
3. Turn the ignition switch OFF.
4. Disconnect the IAC valve 3P connector.
5. Start the engine, and let it idle.
6. Check the engine speed at idle without load conditions; headlights, blower fan, radiator fan, and air conditioner off. Does the idle speed increase or fluctuate? YES - Check the idle speed with a different load condition (electrical, A/C, etc.). If it is out of specification, replace the IAC valve (see «SPECIAL TOOLS»(ref-221324-S23506078702006022400000) ). NO - Replace the IAC valve (see «SPECIAL TOOLS»(ref-221324-S23506078702006022400000) ).

Note. If DTC P0511 is stored at the same time as DTC P0507, troubleshooting DTC P0511 first, then recheck for DTC P0507. Before you troubleshoot, record all freeze data and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).

Scheme 148

1. Start the engine. Hold the engine speed at 3,000 RPM without load (in neutral) until the radiator fan comes on, then let it idle.
2. Check the engine speed at idle without load conditions: headlights, blower fan, radiator fan, and air conditioner off. Is the idle speed 800 +/- 50 RPM? YES - Intermittent failure, system is OK at this time. NO - Go to step 3.
3. Turn the ignition switch OFF.
4. Remove the intake air duct from the throttle body.
5. Start the engine, and let it idle.
6. Put your fingers on the upper and lower ports (A) in the throttle body. Does the idle speed drop below 850 RPM? YES - Check the idle speed with a different load condition (electrical, A/C, etc.). If it is out of specification, replace the IAC valve (see «SPECIAL TOOLS»(ref-221324-S23506078702006022400000) ). NO - Check for vacuum leaks at these parts: PCV valve PCV hose EVAP canister purge valve Intake manifold Throttle body Brake booster hose

Starter Switch Signal Circuit Troubleshooting

Note. The clutch pedal must be pressed.

Scheme 149

1. Measure voltage between ECM connector terminals A24 and B20 with the ignition switch in the ON (II) position and the engine start button pressed. Is there battery voltage? YES - The starter switch signal is OK. NO - Go to step 2.
2. Inspect the No. 21 STARTER SIGNAL (7.5 A) fuse in the under-dash fuse/relay box. Is the fuse OK ? YES - Repair open in the wire between the ECM (A24) and the No. 21 STARTER SIGNAL (7.5 A) fuse. NO - Repair short in the wire between the ECM (A24) and the No. 21 STARTER SIGNAL (7.5 A) fuse or the PGM-FI main relay. Replace the No. 21 STARTER SIGNAL (7.5 A) fuse.

Scheme 150

Scheme 151

Scheme 152

Scheme 153

1. Turn the ignition switch ON (II).
2. Measure voltage between ECM connector terminals A26 and B20. Is there battery voltage? YES - Go to step 6 . NO - Go to step 3.
3. Start the engine.
4. Turn the steering wheel to the full lock position.
5. Measure voltage between ECM connector terminals A26 and B20. Is there battery voltage briefly? YES - The EPS signal is OK. NO - Go to step 10 .
6. Turn the ignition switch OFF.
7. Disconnect the EPS control unit 14P connector.
8. Turn the ignition switch ON (II).
9. Measure voltage between EPS control unit 14P connector terminal No. 13 and body ground. Is there battery voltage? YES - Substitute a known-good EPS control unit and recheck. NO - Repair open in the wire between the ECM (A26) and the EPS control unit.
10. Turn the ignition switch OFF.
11. Disconnect the EPS valve 14P connector.
12. Turn the ignition switch ON (II).
13. Measure voltage between EPS control unit 14P connector terminal No. 13 and body ground. Is there battery voltage? YES - Substitute a known-good EPS control unit and recheck. NO - Go to step 14.
14. Turn the ignition switch OFF.
15. Disconnect ECM connector A (32P).
16. Check for continuity between body ground and ECM connector terminal A26. Is there continuity? YES - Repair short in the wire between the ECM (A26) and the EPS control unit. NO - Substitute a known-good ECM (see «HOW TO SUBSTITUTE THE ECM FOR TESTING PURPOSES»(ref-221328-S04997151962006022400000) ) and recheck. If the voltage is now normal, replace the original ECM (see «ECM REPLACEMENT»(ref-221329-S30667517252006022400000) ).

Scheme 154

1. Check the brake lights. Are the brake lights on without pressing the brake pedal? YES - Inspect the brake pedal position switch adjustment (see «ABS MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION»(ref-221358-S08388719102006022400000) ). 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 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 (A32) and the brake pedal position switch.
4. Inspect the STOP (2000-2001 models: 10 A, 2002-2005 models: 15 A) 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 (2000-2001 models: 10 A, 2002-2005 models: 15 A) fuse. Inspect the brake pedal position switch (see «BRAKE PEDAL POSITION SWITCH TEST»(ref-221390-S26429740012006022400000) ). NO - Repair short in the wire between the ECM (A32) and the STOP (2000-2001 models: 10 A, 2002-2005 models: 15 A) fuse. Replace the STOP (2000-2001 models: 10 A, 2002-2005 models: 15 A) fuse.

Idle Speed Inspection

Note. Leave the IAC valve connected. Before checking the idle speed, check these items: The MIL has not been reported on. Ignition timing Spark plugs Air cleaner PCV system On Canadian models, pull the parking brake lever up. Start the engine, then check that the headlights are off.

Scheme 155

1. Disconnect the EVAP canister purge valve 2P connector.
2. Connect a tachometer.
3. Start the engine. Hold the engine speed at 3,000 RPM without load (in neutral) until the radiator fan comes on, then let it idle.
4. Check the idle speed at idle without load conditions: headlights, blower fan, radiator fan, and air conditioner off. Idle speed should be: 800+/-50 RPM
5. Let the engine idle for 1 minute with high electric load (A/C switch ON, temperature set to Max cool, blower fan on High, and head light on high beam). Idle speed should be: 900+/-50 RPM NOTE: If the idle speed is not within specification, do the symptom troubleshooting.
6. Reconnect the EVAP canister purge valve 2P connector.