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.
2004 Honda S2000 L4-2.2LFACTORY OEM SERVICE PROCEDURE
Idle Learn Procedure
ECM Idle Learn Procedure
The idle learn procedure must be done so that the ECM can learn the engine idle characteristics. Do the idle learn procedure whenever you do any of these actions:
- Disconnect the battery.
- Replace the ECM or disconnect its connector.
- Reset the ECM.
NOTE: Erasing DTCs with HDS does requires the idle learn procedure to be done again.
- Remove the No. 6 ECU (ECM) (15 A) fuse from the under-dash fuse/relay box.
- Remove the No. 41 BATTERY (100 A) fuse from the under-hood fuse/relay box.
- Remove the PGM-FI main relay.
- Remove the battery wire from the under-hood fuse/relay box.
- Disconnect any of the connectors from the under-hood fuse/relay box.
- Disconnect the connector (C404) between the dashboard wire harness A and dashboard wire harness B.
- Disconnect the G1 terminal.
- Adjust the idle speed.
To complete the idle learn procedure do this:
1. Make sure all electrical items (A/C, audio, rear window defogger, lights, etc.) are turned off.
2. Start the engine. Hold the engine speed at 3,000 rpm with no load (in neutral) until the radiator fan comes on, or the engine coolant temperature reaches 176 °F (80 °C) -212 °F (100 °C).
3. Let the engine idle for about 5 minutes with the throttle fully closed and with all electrical items off.
NOTE: If the radiator fan comes on during this step, the time when it is operating must not be included in the 5 minutes.
The idle learn procedure must be done so that the ECM can learn the engine idle characteristics. Do the idle learn procedure whenever you do any of these actions:
- Disconnect the battery.
- Replace the ECM or disconnect its connector.
- Reset the ECM.
NOTE: Erasing DTCs with HDS does requires the idle learn procedure to be done again.
- Remove the No. 6 ECU (ECM) (15 A) fuse from the under-dash fuse/relay box.
- Remove the No. 41 BATTERY (100 A) fuse from the under-hood fuse/relay box.
- Remove the PGM-FI main relay.
- Remove the battery wire from the under-hood fuse/relay box.
- Disconnect any of the connectors from the under-hood fuse/relay box.
- Disconnect the connector (C404) between the dashboard wire harness A and dashboard wire harness B.
- Disconnect the G1 terminal.
- Adjust the idle speed.
To complete the idle learn procedure do this:
1. Make sure all electrical items (A/C, audio, rear window defogger, lights, etc.) are turned off.
2. Start the engine. Hold the engine speed at 3,000 rpm with no load (in neutral) until the radiator fan comes on, or the engine coolant temperature reaches 176 °F (80 °C) -212 °F (100 °C).
3. Let the engine idle for about 5 minutes with the throttle fully closed and with all electrical items off.
NOTE: If the radiator fan comes on during this step, the time when it is operating must not be included in the 5 minutes.
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.
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