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.
How to End a Troubleshooting Session
2004 Honda S2000 L4-2.2LSECTION How to End a Troubleshooting Session
How to Reset the ECM
You can reset the ECM in either of two ways:
NOTE: After resetting the ECM, do the ECM idle learn procedure.
Reset the ECM with the OBD II scan tool or HDS
1. Turn the ignition switch ON (II). Do not start the engine.
2. Use an OBD II scan tool or HDS to clear the DTC.
NOTE: For the specific operations, refer to the user's manual that came with a scan tool or HDS.
Reset the ECM by removing the fuse
1. Turn the ignition switch OFF.
2. Remove the No. 25 BACK UP (7.5 A) fuse (A) from the under-dash fuse/relay box (B) for 60 seconds.
How to End a Troubleshooting Session (required after any troubleshooting)
1. Reset the ECM as described above.
2. Turn the ignition switch OFF.
3. Disconnect an OBD II scan tool or HDS from the data link connector (DLC).
NOTE:
- The ECM is part of the immobilizer system. If you replace the ECM, it will have a different immobilizer code. In order for the engine to start, you must rewrite the immobilizer code with the HDS.
- Do the idle learn procedure.
You can reset the ECM in either of two ways:
NOTE: After resetting the ECM, do the ECM idle learn procedure.
Reset the ECM with the OBD II scan tool or HDS
1. Turn the ignition switch ON (II). Do not start the engine.
2. Use an OBD II scan tool or HDS to clear the DTC.
NOTE: For the specific operations, refer to the user's manual that came with a scan tool or HDS.
Reset the ECM by removing the fuse
1. Turn the ignition switch OFF.
2. Remove the No. 25 BACK UP (7.5 A) fuse (A) from the under-dash fuse/relay box (B) for 60 seconds.
How to End a Troubleshooting Session (required after any troubleshooting)
1. Reset the ECM as described above.
2. Turn the ignition switch OFF.
3. Disconnect an OBD II scan tool or HDS from the data link connector (DLC).
NOTE:
- The ECM is part of the immobilizer system. If you replace the ECM, it will have a different immobilizer code. In order for the engine to start, you must rewrite the immobilizer code with the HDS.
- Do the idle learn procedure.
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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.