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Old 04-28-2010, 05:50 PM   #1
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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.
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Old 04-28-2010, 05:54 PM   #2
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Or just disconnect the negative battery cable, hold down the brakes for a few seconds, and then reconnect negative battery cable. It does the same thing, the ECU resets itself and for the next 50 warm up periods it will relearn everything.
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Old 04-28-2010, 06:13 PM   #3
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Or just disconnect the negative battery cable, hold down the brakes for a few seconds, and then reconnect negative battery cable. It does the same thing, the ECU resets itself and for the next 50 warm up periods it will relearn everything.
How does this work?
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Old 07-08-2012, 12:59 AM   #4
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I am already averaging about 18.5 mpg in my '91 Cherokee(227,000 miles). I put new plugs/wires in about 5000 miles ago and made an exhaust modification. Is it necessary for me to reset the ECU?
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Old 07-08-2012, 08:40 AM   #5
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Originally Posted by gardnern99
I am already averaging about 18.5 mpg in my '91 Cherokee(227,000 miles). I put new plugs/wires in about 5000 miles ago and made an exhaust modification. Is it necessary for me to reset the ECU?
No. You didn't increase the air-fuel-spark ratio, so no need for computer to do anything different. And even if your exhaust is more "free flowing", there is still no increase in intake volume, so nothing really changes except (potentially) back pressure. Which, if you remove too much back pressure without increasing intake volume, your performance will suffer..
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Old 07-08-2012, 10:48 AM   #6
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You'll need to see a mechanic or dealer for a "deep reset" however. If this were your average computer... This technique more or less "clears the cache".

I had to do this after installing my CPS. Tried this technique and it just made it run worse.
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Old 07-08-2012, 11:41 AM   #7
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Old 07-08-2012, 12:03 PM   #8
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You'll need to see a mechanic or dealer for a "deep reset" however. If this were your average computer... This technique more or less "clears the cache".

I had to do this after installing my CPS. Tried this technique and it just made it run worse.
You mean it made run worse than before changing the CPS? Could you elaborate?
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Old 07-08-2012, 12:03 PM   #9
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I've seen posted you might just leave it disconnected overnight to "let the capacitors bleed down". No idea myself except it sounds easy and harmless.

Yea^, never heard if trying to clear anything because of the cps....
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