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DIY engine computer reset.

415K views 67 replies 47 participants last post by  purcellsj.57 
#1 · (Edited by Moderator)
There has been a lot of posts in the last fw months about codes and reseting the computers without paying VW $60 to do it. well for the DIY here is a home remedy, unfortunatley this does not allow you to read the codes but however it does allow you to reset teh computer to the same position as if the dealer would.

I learned this procedure from a very reliable source at VWOA. 8)

1) remove both the Positive and teh negative battery terminals from the battery.

2) Wait 15 seconds then touch the 2 removed battery leads together and hold for 10 seconds then seperate. (This immatated the same capicitor discharge that is involved with the Vagcom reset)

3) replace and reattach the terminals to the battery

4) stick key in ignition and turn to ignition on (DO NOT START THE CAR) and leave in this position for 30 seconds to allow the newely reset computer to re-learn the parts of your vehicle.

5) Enjoy not having a check engine light staring you in your face.

I have done this procedure countless times now during the rebuild, changing and modification process of my motor, trans and turbo and saved me a lot of time and headaches. 😉
 
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#9 ·
We tried this procedure several times on my friends AEB 98 1.8t to reset his airbag light and check engine light. It didn't work for us. The check engine light eventually went off by itself during a long drive and the airbag light is still on to this day.
 
#10 ·
A little-known extra step in this procedure is that the driver's door must be open during the "ignition on" step. Since the door usually remains open to make it easier to hop in and out of the car during this procedure, almost everyone manages to perform the procedure without having to consider that point.

But, if you've not been able to get this procedure to work, you might want to see if you been leaving the door open. VW wrote the code this way so resets wouldn't happen during normal operations with the door closed.
 
#11 ·
gojimbo said:
A little-known extra step in this procedure is that the driver's door must be open during the "ignition on" step. Since the door usually remains open to make it easier to hop in and out of the car during this procedure, almost everyone manages to perform the procedure without having to consider that point.

But, if you've not been able to get this procedure to work, you might want to see if you been leaving the door open. VW wrote the code this way so resets wouldn't happen during normal operations with the door closed.
Thanks !
 
#14 · (Edited by Moderator)
gojimbo said:
A little-known extra step in this procedure is that the driver's door must be open during the "ignition on" step. Since the door usually remains open to make it easier to hop in and out of the car during this procedure, almost everyone manages to perform the procedure without having to consider that point.

But, if you've not been able to get this procedure to work, you might want to see if you been leaving the door open. VW wrote the code this way so resets wouldn't happen during normal operations with the door closed.
if you have specific information from VW regarding that part of the procedure please share it. Otherwise, the whole door open thing is probably an urban legend. FWIW, I never once heard it mentioned on Audiworld.

In the "B5 garage" there is a recent discussion on throttle body alignment/adaption:

http://www.passatworld.com/forums/showthread.php?t=172629
 
#31 · (Edited by Moderator)
You might need an o2 spacer or some other method, because resetting it would reset the readiness codes, and the CEL would come back.

Not doing this until someone else has the balls to try it with their DPP'd APR program :nervous: but absolutely GREAT info....I need this to get rid of my SAIP CEL
Again, would this jack up the APR program?
Resetting the ECU should not remove the APR program.

With regards to cost of a reflash, this is up to the dealer; some are free, others charge.
 
#21 ·
I recently reset the check engine by accident when changing the battery as explained by the original poster. The reason for the CEL was a faulty secondary air pump. Now that the CEL is off (temporarily I presume), will the state inspector catch the issue during a regular vehicle inspection?

Therefore, does the computer get purged of all historical CEL warnings? Or does it maintain a log of historical warnings? Can the state inspector force a system check that will catch the faulty secondary air pump?

Thanks for your input!
 
#22 ·
Now that the CEL is off (temporarily I presume), will the state inspector catch the issue during a regular vehicle inspection?
No history is stored, but you may have an issue at the inspector if they check for readiness codes. When you reset a check engine light, it basically sets the OBD-II system into a state that says "I've got no codes, but I haven't had a chance to run all of my self tests yet." Readiness codes can only be set through a couple of days of driving.

In some states, you will be told to come back in a couple of days because tey honor the readiness codes. I can tell you for a fact that in CT, they don't care.
 
#23 · (Edited by Moderator)
The state inspector can't force a system check. Once the codes have been cleared there is no way to look in the pcm to find out what codes may have been stored previously. Your car may still fail emissions even though the cel is off. All cars(96 and newer MY) have a set of what we call readiness monitors, these are test results of various systems on the car such as o2 sensor, catalytic converter, evap system and so forth. Depending on a vehicles equipment some may have more readiness monitors than others.

When you take your car through emissions you can have no more than 2 readiness monitors that have not completed and passed, at least in AZ and CA. Readiness monitors run at a predetermined time when certain criteria have been met. It is possible for a readiness monitor to take a week or more to run and complete according to your driving habits. So in your case with the secondary air injection fault the pcm is going to run it's test for 90 seconds when the vehicle is first started and after it has completed a cool down cycle. I believe this is a 2 trip monitor which means that this test has to have ran and failed 2 consecutive times in order to turn on the cel.
 
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