The following procedures will allow you to clear the ECU memory as well as erase any DTC codes which may illuminate your SERVICE ENGINE SOON lamp. This will clear the following data:

- DTC's (Diagnostic trouble codes)- 1st trip diagnostic trouble codes- Freeze frame data- 1st trip freeze frame data- SRT (system readiness test) codes- Test Values

The following procedures are effective for both the R50 and R51 models. It is recommended that after completion of the reset procedure you complete the "Accelerator Pedal Released Position Learning" (If applicable), "Throttle Valve Closed Position Learning" (If Applicable) and "Idle Air Volume Learning" procedures as this data will also be erased and may need to be relearned.

Below are three separate procedures, any one of which will successfully clear your ECU's memory. Only one of the procedures needs to be performed. If an error occurs during reset procedure, you can start the procedure over without harming ECU. The following procedures will only clear emission-related DTC's.

The first procedure is the most difficult and time sensitive of the three. This procedure (if chosen) must be timed accurately or you may get a DTC and the SERVICE ENGINE SOON lamp will illuminate. It is recommended that you use a timer or stopwatch, if neither is accessible then implement accurate counting methods (one one-hundred, two one-hundred, etc..). The second procedure is medium difficulty and is still somewhat time sensitive. The second method is a variation of the first method using simpler timing which allows for easier counting (no need for timer or stop watch). It is still suggested that you use accurate counting method for the second procedure (one one-hundred, two one-hundred, etc..). The third procedure is the easiest of all and requires almost no effort. This method is recommended if the vehicle is not needed for use. It is required that you wait a full 24 hours to reconnect the battery as this will ensure that all memory has been erased.

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METHOD ONE (Most difficult procedure):"]______________________________________________

1. Confirm that accelerator pedal is fully released, turn ignition switch “ON” (without starting vehicle) and wait 3 seconds.

2. Repeat the following steps (2a and 2b) procedures quickly five times within 5 seconds.

2-a. Fully depress the accelerator pedal (HARD).2-b. Fully release the accelerator pedal.

3. Wait 7 seconds, fully depress the accelerator pedal and keep it for approximately 10 seconds until SERVICE ENGINE SOON starts blinking.

4. Fully release the accelerator pedal (while SERVICE ENGINE SOON is still blinking).

5. Wait about 10 seconds.

6. Fully depress the accelerator pedal and keep it for more than 10 seconds.

7. Fully release the accelerator pedal (The SERVICE ENGINE SOON light will continue to blink).

8. Turn ignition switch to “OFF” position and now you can start the vehicle. The SERVICE ENGINE SOON light should be gone.

If the SERVICE ENGINE SOON light continues to remain ON, repeat the above steps. Timing is EXTREMELY critical to resetting the ECU.

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METHOD TWO (Medium difficulty):"]______________________________________________

1. Turn ignition "ON" (without starting vehicle), count to 3 seconds.

2. Depress/Release accelerator pedal 5 times...hard and fast.

3. Count to 10 seconds (not 7!) and fully depress accelerator pedal.

4. Count to 12 seconds (SERVICE ENGINE SOON should be blinking), release accelerator pedal.

5. Count to 10 seconds, depress accelerator pedal.

6. Count to 10 seconds, release accelerator pedal.

7. Turn off ignition, then start engine. Done!

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METHOD THREE (Extremely Simple):"]______________________________________________

1. Remove negative battery cable from vehicle battery.

2. Allow vehicle to sit for at least 24 hours with negative cable disconnected.

3. After 24 hours, reconnect negative cable to battery.

Good Luck!

Another awesome "How To:", thanks!

Billy

thanks for the info!!!

Good stuff!!!!!!!!!!!!Thanks

24 hours for the ECU to reset with the battery disconnected? It REALLY takes that long??

Yes and no, the FSM suggests 24 hours for complete erasure. I have had a couple of instances where I did have to leave it overnight to clear my DTC's completely. Others say you can just unplug the negative cable and pump the brakes a few times to clear them, I've never tried that. I don't even really recommend the battery procedure of clearing DTC's but people like doing that instead of the other two procedures because it's easier.

i have honestly left my battery cable off for more than 48 hours and it did not erase anything.

slickroger wrote:i have honestly left my battery cable off for more than 48 hours and it did not erase anything.

Yeah, that is part of the reason why I don't really recommend the battery procedure to erase DTC's. Whenever I used to disconnect my battery overnight it wouldn't ever clear the ECU memory. When I installed my remote starter/alarm system the battery stayed disconnected for 3-4 days and when I reconnected it the ECU memory had been completely erased. Now when I leave the battery disconnected overnight it clears the ECU memory within 24 hours. I have never been able to clear the ECU memory by just unplugging the battery for a short period of time. Regardless, methods 1 and 2 above are much faster and ensure that the ECU has been 100% erased. Once you do the accelerator pedal methods a couple of times you get the hang of it and you can do it in your sleep.

4th option. use a OBD2 reader/scanner and erase codes that way.

plug in. find codes. erase. unplug.

Thanks for all the info. I have an AutoZone that is close and I will need to probably buy an O2 Sensor anyway.

Method 1 was an awesome surprise. Reminds me of using cheat codes on video games. It worked perfectly. Thank you.

Method I worked on a 2002 Infiniti QX4 4x4.

Thanks.

I have a 05 pathfinder and used that method 1 , 2 , or method 3 to clear my service engine soon light and it worked great. Timing the procedure correct is a must though. Mine worked on the method 2 procedure.Thanks for the info guys!

Understand this thread is old but would this procedure or or should be taken when replacing an ECU on a 97 q45?

Huge Thanks! You Rock!
#1 Worked like a champ on my 2003 Chilkoot Edition.