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.
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HOMESERVICE MANUALSHONDA2005CIVIC L4-1.7L CNGREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSRELAYS AND MODULES - COMPUTERS AND CONTROL SYSTEMSENGINE CONTROL MODULETESTING AND INSPECTIONPROGRAMMING AND RELEARNINGUPDATING THE PCM
2005 Honda Civic L4-1.7L CNG
Updating the PCM
2005 Honda Civic L4-1.7L CNGSECTION Updating the PCM
PCM Updating, Substitution and Replacement
Special Tools Required
Honda interface module (HIM) P/N EQS05A35570
Use this procedure when you have to substitute a known-good PCM in a troubleshooting procedure. Update the PCM only if the PCM does not already have the latest software loaded.
NOTE: Do not turn the ignition switch OFF while updating; the PCM can be damaged.
How to Update the PCM
NOTE:
- To ensure the latest program is installed, do PCM update whenever the PCM is substituted or replaced.
- Before you update the PCM. make sure the vehicle's battery is fully charged.
- To prevent PCM 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 PCM 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 PCM update procedure as described on the HIM label and in the PCM update system. If the software in the PCM is the latest version, replace the PCM.
How to Substitute or Replace the PCM
1. Turn the ignition switch OFF.
2. Remove the passenger's dashboard lower cover, the right kick panel and the glove box.
3. Remove the bolt. Cut the plastic cross brace in the glove box opening with diagonal cutters in the area shown, and discard it.
4. Remove the relays (A), then remove the bolts and the glove box frame (B).
5. Remove the gray 20P PCM wire harness connector from the PCM mounting bracket. Remove the PCM mounting bolt (A) and the bracket.
6. Remove the nuts, then remove the PCM (B).
7. Install the PCM in the reverse order of removal.
8. Connect the HDS to the DLC (A) located under the driver's side of dashboard.
9. Turn the ignition switch ON (II).
NOTE: For 2004-2005 models: DTC P0630 "VIN Not Programmed or Mismatch" will be stored because a VIN has not been programmed into the PCM, but ignore it and continue this procedure.
10. Input the VIN to the PCM with the HDS.
11. Rewrite the immobilizer code with the PCM replacement procedure in the HDS; it allows you to start the engine.
12. Reset the PCM with the HDS.
13. Do the PCM idle learn procedure.
Special Tools Required
Honda interface module (HIM) P/N EQS05A35570
Use this procedure when you have to substitute a known-good PCM in a troubleshooting procedure. Update the PCM only if the PCM does not already have the latest software loaded.
NOTE: Do not turn the ignition switch OFF while updating; the PCM can be damaged.
How to Update the PCM
NOTE:
- To ensure the latest program is installed, do PCM update whenever the PCM is substituted or replaced.
- Before you update the PCM. make sure the vehicle's battery is fully charged.
- To prevent PCM 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 PCM 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 PCM update procedure as described on the HIM label and in the PCM update system. If the software in the PCM is the latest version, replace the PCM.
How to Substitute or Replace the PCM
1. Turn the ignition switch OFF.
2. Remove the passenger's dashboard lower cover, the right kick panel and the glove box.
3. Remove the bolt. Cut the plastic cross brace in the glove box opening with diagonal cutters in the area shown, and discard it.
4. Remove the relays (A), then remove the bolts and the glove box frame (B).
5. Remove the gray 20P PCM wire harness connector from the PCM mounting bracket. Remove the PCM mounting bolt (A) and the bracket.
6. Remove the nuts, then remove the PCM (B).
7. Install the PCM in the reverse order of removal.
8. Connect the HDS to the DLC (A) located under the driver's side of dashboard.
9. Turn the ignition switch ON (II).
NOTE: For 2004-2005 models: DTC P0630 "VIN Not Programmed or Mismatch" will be stored because a VIN has not been programmed into the PCM, but ignore it and continue this procedure.
10. Input the VIN to the PCM with the HDS.
11. Rewrite the immobilizer code with the PCM replacement procedure in the HDS; it allows you to start the engine.
12. Reset the PCM with the HDS.
13. Do the PCM 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.