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.
ECM Reset
2005 Honda Accord L4-2.4LSECTION ECM Reset
HDS Clear Command
The ECM/PCM stores various specific data to correct the system even if there is no electrical power such as when the battery negative terminal or No.8 FI ECU (ECM/PCM) (15 A) fuse are disconnected. Stored data based on failed parts should be cleared by using the "CLEAR COMMAND" of the HDS, if parts are replaced.
The HDS has three kinds of clear commands to meet this purpose. They are DTC clear, ECM/PCM clear, and CKP pattern clear. DTC clear command erases all stored DTC codes, freeze data, and readiness codes. This must be done with the HDS after reproducing the DTC during troubleshooting.
The ECM/PCM clear command erases all stored DTC codes, freeze data, readiness codes, and all specific data to correct the system except CKP pattern. If the CKP pattern data in the ECM/PCM was cleared, you must do the CKP pattern learn procedure. The CKP pattern clear command erases only CKP pattern data. This command is for repair of a misfire or the CKP sensor.
DTC CLEAR
1. Clear the DTC with the HDS while the engine is stopped.
2. Turn the ignition switch OFF.
3. Turn the ignition switch ON (II). Wait for 30 seconds.
4. Turn the ignition switch OFF, and disconnect the HDS from the DLC.
ECM/PCM RESET
This command clears stored specific data from each vehicle such as DTCs, freeze data, and readiness codes. It does not clear CKP PATTERN data.
1. Reset the ECM/PCM with the HDS while the engine is stopped.
2. Turn the ignition switch OFF.
3. Turn the ignition switch ON (II), and wait for 30 seconds.
4. Turn the ignition switch OFF, and disconnect the HDS from the DLC.
5. Do the ECM/PCM idle learn procedure.
CKP PATTERN CLEAR/CKP Pattern Learn
NOTE: The ECT needs to be at 176 °F (80 °C) or higher.
1. Clear the CKP pattern while the engine is stopped.
2. Turn the ignition switch OFF.
3. Turn the ignition switch ON (II), and wait for 30 seconds.
4. Test-drive the vehicle on a level road: decelerate (with the throttle fully closed) from an engine speed of 2,500 rpm to 1,000 rpm with the A/T in 2 position, or M/T in 1st gear.
5. Stop the vehicle, but keep the engine running.
6. Check PULSER F/B LEARN in the DATA LIST with the HDS. If it is NOT COMPLETED, go to step 4. If it is COMPLETED, go to step 7.
7. Turn the ignition switch OFF.
8. Turn the ignition switch ON (II), and wait for 30 seconds. The CKP learning procedure is completed.
How to End a Troubleshooting Session (required after any troubleshooting)
1. Reset the ECM/PCM with the HDS.
2. Do the ECM/PCM idle learn procedure.
3. Turn the ignition switch OFF.
4. Disconnect the HDS from the DLC.
NOTE: The ECM/PCM is part of the immobilizer system. If you replace the ECM/PCM, it will have a different immobilizer code. In order for the engine to start, you must rewrite the immobilizer code with the HDS.
The ECM/PCM stores various specific data to correct the system even if there is no electrical power such as when the battery negative terminal or No.8 FI ECU (ECM/PCM) (15 A) fuse are disconnected. Stored data based on failed parts should be cleared by using the "CLEAR COMMAND" of the HDS, if parts are replaced.
The HDS has three kinds of clear commands to meet this purpose. They are DTC clear, ECM/PCM clear, and CKP pattern clear. DTC clear command erases all stored DTC codes, freeze data, and readiness codes. This must be done with the HDS after reproducing the DTC during troubleshooting.
The ECM/PCM clear command erases all stored DTC codes, freeze data, readiness codes, and all specific data to correct the system except CKP pattern. If the CKP pattern data in the ECM/PCM was cleared, you must do the CKP pattern learn procedure. The CKP pattern clear command erases only CKP pattern data. This command is for repair of a misfire or the CKP sensor.
DTC CLEAR
1. Clear the DTC with the HDS while the engine is stopped.
2. Turn the ignition switch OFF.
3. Turn the ignition switch ON (II). Wait for 30 seconds.
4. Turn the ignition switch OFF, and disconnect the HDS from the DLC.
ECM/PCM RESET
This command clears stored specific data from each vehicle such as DTCs, freeze data, and readiness codes. It does not clear CKP PATTERN data.
1. Reset the ECM/PCM with the HDS while the engine is stopped.
2. Turn the ignition switch OFF.
3. Turn the ignition switch ON (II), and wait for 30 seconds.
4. Turn the ignition switch OFF, and disconnect the HDS from the DLC.
5. Do the ECM/PCM idle learn procedure.
CKP PATTERN CLEAR/CKP Pattern Learn
NOTE: The ECT needs to be at 176 °F (80 °C) or higher.
1. Clear the CKP pattern while the engine is stopped.
2. Turn the ignition switch OFF.
3. Turn the ignition switch ON (II), and wait for 30 seconds.
4. Test-drive the vehicle on a level road: decelerate (with the throttle fully closed) from an engine speed of 2,500 rpm to 1,000 rpm with the A/T in 2 position, or M/T in 1st gear.
5. Stop the vehicle, but keep the engine running.
6. Check PULSER F/B LEARN in the DATA LIST with the HDS. If it is NOT COMPLETED, go to step 4. If it is COMPLETED, go to step 7.
7. Turn the ignition switch OFF.
8. Turn the ignition switch ON (II), and wait for 30 seconds. The CKP learning procedure is completed.
How to End a Troubleshooting Session (required after any troubleshooting)
1. Reset the ECM/PCM with the HDS.
2. Do the ECM/PCM idle learn procedure.
3. Turn the ignition switch OFF.
4. Disconnect the HDS from the DLC.
NOTE: The ECM/PCM is part of the immobilizer system. If you replace the ECM/PCM, it will have a different immobilizer code. In order for the engine to start, you must rewrite the immobilizer code with the HDS.
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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.