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.
Updating the ECM
2005 Honda Civic Si L4-2.0LSECTION Updating the ECM
ECM Updating and Substitution for Testing
Special Tools Required
Honda interface module (HIM) P/N EQS05A35570
Use this procedure when you have to substitute a known-good ECM in a troubleshooting procedure. Update the ECM only if the ECM does not already have the latest software loaded.
NOTE: Do not turn the ignition switch OFF while updating; the ECM can be damaged.
How to Update the ECM
NOTE:
- To ensure the latest program is installed, do an ECM update whenever the ECM is substituted or replaced.
- Before you update the ECM, make sure the vehicle's battery is fully charged.
- To prevent ECM damage, do not operate anything electrical (audio system, brakes, A/C, power windows, moonroof, door locks, etc.) during the update.
- If you need to diagnose the Honda interface module (HIM) because the HIM's red (#3) light came on or was flashing during the update, leave the ignition switch in the ON (II) position when you disconnect the HIM from the data link connector (DLC). This will prevent ECM damage.
1. Turn the ignition switch ON (II). Do not start the engine.
2. Connect the HIM to the DLC (A) located under the driver's side of dashboard.
3. Do the ECM update procedure as described on the HIM label and in the ECM update system. If the software in the ECM is the latest version, replace the ECM.
How to Substitute the ECM
1. Remove the passenger's dashboard lower cover, the passenger's kick panel, and the glove box.
2. Disconnect the connectors (A) and remove the ECM mounting bolts (B).
3. Remove the ECM (C).
4. Install a known-good ECM in the reverse order of removal.
5. Turn the ignition switch ON (II).
NOTE: If DTC: P0630 "VIN Not Programmed or Mismatch" is stored at this time, ignore it and continue this procedure.
6. Input the VIN to the ECM with the HDS.
7. Rewrite the immobilizer code with the ECM replacement procedure in the HDS; it allows you to start the engine.
8. After completing your tests, reinstall or replace the original ECM, and rewrite the immobilizer code using the ECM replacement procedure in the HDS.
9. Do the ECM idle learn procedure.
Special Tools Required
Honda interface module (HIM) P/N EQS05A35570
Use this procedure when you have to substitute a known-good ECM in a troubleshooting procedure. Update the ECM only if the ECM does not already have the latest software loaded.
NOTE: Do not turn the ignition switch OFF while updating; the ECM can be damaged.
How to Update the ECM
NOTE:
- To ensure the latest program is installed, do an ECM update whenever the ECM is substituted or replaced.
- Before you update the ECM, make sure the vehicle's battery is fully charged.
- To prevent ECM damage, do not operate anything electrical (audio system, brakes, A/C, power windows, moonroof, door locks, etc.) during the update.
- If you need to diagnose the Honda interface module (HIM) because the HIM's red (#3) light came on or was flashing during the update, leave the ignition switch in the ON (II) position when you disconnect the HIM from the data link connector (DLC). This will prevent ECM damage.
1. Turn the ignition switch ON (II). Do not start the engine.
2. Connect the HIM to the DLC (A) located under the driver's side of dashboard.
3. Do the ECM update procedure as described on the HIM label and in the ECM update system. If the software in the ECM is the latest version, replace the ECM.
How to Substitute the ECM
1. Remove the passenger's dashboard lower cover, the passenger's kick panel, and the glove box.
2. Disconnect the connectors (A) and remove the ECM mounting bolts (B).
3. Remove the ECM (C).
4. Install a known-good ECM in the reverse order of removal.
5. Turn the ignition switch ON (II).
NOTE: If DTC: P0630 "VIN Not Programmed or Mismatch" is stored at this time, ignore it and continue this procedure.
6. Input the VIN to the ECM with the HDS.
7. Rewrite the immobilizer code with the ECM replacement procedure in the HDS; it allows you to start the engine.
8. After completing your tests, reinstall or replace the original ECM, and rewrite the immobilizer code using the ECM replacement procedure in the HDS.
9. Do the ECM 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.