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Reseting ECU

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Old 10-24-2010, 09:06 PM
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Originally Posted by chilixj99
I searched but couldn't find the steps on how to reset the ECU. Thanks.
RENIX - 1987-1990. No procedure necessary, the ECU resets with key cycling and does not store data or DTCs.

OBD - 1991-2001. Remove both battery cables from the battery, and touch them together for thirty seconds. This drains the caps for the Keep-Alive Memory (KAM) and effectively resets the thing.

NB: OBD ECUs may also be reset using the appropriate scanner tool. However, the DTC reset caused by the scantool tends to not reset the "learned operating data" (fuel trims and the like,) thus eliminating the relearn process. This is ultimately simpler than the full KAM reset - I'd suggest only doing the full KAM reset if you're having trouble that can't otherwise be identified (which may mean that data has been "mislearned" and needs to be "relearned.) Expect things to be a bit funny for the first fortnight or so after a full KAM reset...
Old 10-24-2010, 09:14 PM
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Exactly how long is a fortnight??
Old 10-24-2010, 10:16 PM
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Originally Posted by chilixj99
Exactly how long is a fortnight??
14 days
Old 10-24-2010, 11:01 PM
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Originally Posted by 5-90
RENIX - 1987-1990. No procedure necessary, the ECU resets with key cycling and does not store data or DTCs.

OBD - 1991-2001. Remove both battery cables from the battery, and touch them together for thirty seconds. This drains the caps for the Keep-Alive Memory (KAM) and effectively resets the thing.

NB: OBD ECUs may also be reset using the appropriate scanner tool. However, the DTC reset caused by the scantool tends to not reset the "learned operating data" (fuel trims and the like,) thus eliminating the relearn process. This is ultimately simpler than the full KAM reset - I'd suggest only doing the full KAM reset if you're having trouble that can't otherwise be identified (which may mean that data has been "mislearned" and needs to be "relearned.) Expect things to be a bit funny for the first fortnight or so after a full KAM reset...
thanks! now i know for sure that this is what you have to do. i've always thought so but never knew for sure
Old 10-25-2010, 02:24 AM
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Originally Posted by chilixj99
Exactly how long is a fortnight??
Why, it's twice a sen'night!
Old 10-25-2010, 04:44 AM
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nothing good can come from touching a pos and neg wire together from something that stores current
Old 10-25-2010, 07:26 AM
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Originally Posted by freegdr
nothing good can come from touching a pos and neg wire together from something that stores current
I would be afraid of the tracers burning off the board.
Old 10-25-2010, 07:56 AM
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Originally Posted by Dwinthrup
I would be afraid of the tracers burning off the board.
That is the method recommended - http://www.quadratec.com/jeep_knowle...article-89.htm


Jeep Electronic Control Unit Reset
When installing new power or performance accessories how does the computer for the Jeep know that it has a new accessory? Most of the time the computer does not. The computer would need to be reset to take full potential of the performance accessories you have added.

The Electronic Control Module, or ECU as its commonly called, stores the information for your vehicle and your driving habits in its memory. The memory is maintaned by a series of capacitors that hold a charge and maintain power for the ECU when the vehicle is turned off. The following procedure will allow you to reset the memory and allow the computer to 're-learn' how to drive by adjusting to the drivers habits and the vehicles modifications.


1. Disconnect the battery by removing the positive battery cable. Remember, the positive battery cable.

2. Ground the positive cable to the negative cable for 30 seconds to erase the electric charge in the capacitors.

3. Reconnect the positive cable to the battery.

4. Turn the key to on but do not start.

5. Turn the headlights on.

6. Turn the headlights off.

7. Turn the key off.


The ECU has now been reset to its factory settings. For the next 50 warm-up periods the ECU will re-learn the engine and driving habits for your driving conditions and the newly installed parts.
Old 05-12-2013, 06:55 AM
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I realize this thread is a few years old but just to add my two cents, I have used this method on my '90 Cherokee with no problem and it cleared the ECU perfectly.
Old 06-28-2020, 02:55 PM
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Originally Posted by chilixj99
Pretty sure you don't do that. I think you just take off the negative cable for a little bit, but not sure if that's all. I've heard you take the negative off and touch it to the positive while the positive is still attached. Anyone??
No , it's disconnect the Positive and touch the Negative and hold it there for 30 seconds , reconnect the Positive , Now turn the ignition to on BUT DON'T Start it , turn you head light's on then off turn ignition off - Now it's reset - Start engine on , fot the next 40 or so warm ups and Driving , your vehicle will learn how you drive - Peace -
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