Best and correct method to reset ECM? - JeepForum.com
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post #1 of 18 Old 04-20-2008, 07:50 AM Thread Starter
scratch068
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Best and correct method to reset ECM?

I've read disconnect battery cables and touch for 10 minutes, disconnect neg cable and turn key on/off 3 times and disconnect battery cables and leave lights on for 10 minutes.

Which one or better method? Or do they all work equally well?

mm


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post #2 of 18 Old 04-20-2008, 08:25 AM
AZ Jeff
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Just leaving the battery disconnected for about 30 minutes clears all codes just fine (assuming the faults that were present beforehand are fixed).

AZ-Jeff
I don't own an XJ any longer, but I still think they are the best of all the Jeep products ever made. My XJ was my favorite vehicle in my 50+ years of driving.
So...I stick around and give advice.
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post #3 of 18 Old 04-20-2008, 08:41 AM
CJ7-Tim
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This procedure will erase the 1996+ OBD-II "Adaptive Memory" stored inside the PCM and allow a new "Adaptive Memory" to be developed. After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics. Perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn adaptive mode.

Disconnect the POSITIVE battery Terminal clamp and firmly touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory).

Reconnect the Battery Cable
Turn Ignition Switch to the "ON" position but DO NOT start the engine
Turn Headlight "ON"
Turn Headlights "OFF"
Turn Ignition Key "OFF"
 
The PCM Adaptive memory has now been flashed, or erased from the PCM. When you start the engine it will be running off pre-programmed data tables that come with the PCM from the factory. When the engine gets up to operating temperature the PCM will start to collect and store new data for the Adaptive Memory.








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Last edited by CJ7-Tim; 06-15-2009 at 01:58 PM.
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post #4 of 18 Old 04-20-2008, 09:43 AM
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Tim,

Excellent info! Did you happen to get the years this procedure covers?

Wm
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post #5 of 18 Old 04-20-2008, 09:49 AM
CJ7-Tim
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I know this works on 1996+ OBD-II PCMs. I have never owned an older Cherokee so I don't know exactly how far back this works. I would guess that it is only for the OBD-II systems.

“We the people are the rightful masters of both Congress and the Courts,
not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #6 of 18 Old 04-21-2008, 08:58 PM Thread Starter
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Update on ECM reset

My check engine light is on now, is this because the thing is in leanring mode?

mm

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post #7 of 18 Old 10-13-2008, 10:59 PM
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best way = https://www.jeepforum.com/forum/showthread.php?t=548305

my jeep has the confused prerunner syndrome....4.5" in the rear and 2" in the front.

Purple Jeep Club Member # 1
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post #8 of 18 Old 10-13-2008, 11:03 PM
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that same procedure worked for my 91' cherokee..dunno about older cherks tho.

Dunno why your check engine light went off when you reset the comp, did you have a check engine light before cuz it should have cleared? Too bad you cant get codes read for free anymore :/. or maybe your state dosent have that law..
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post #9 of 18 Old 02-27-2009, 05:02 PM
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Ground

WHat do you mean specifically when you say to touch the posisitve terminal to "ground".
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post #10 of 18 Old 12-24-2010, 12:22 AM
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The engine block or the A/C compressor pump will work as a ground.

-R.I.P
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post #11 of 18 Old 12-24-2010, 03:06 AM
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Quote:
Originally Posted by waubeno52 View Post
WHat do you mean specifically when you say to touch the posisitve terminal to "ground".
Disconnect the positive CABLE from the battery and then touch it to ground (fender, engine block, etc.)

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post #12 of 18 Old 12-24-2010, 10:50 AM
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Quote:
Originally Posted by CJ7-Tim View Post
Disconnect the POSITIVE battery Terminal and touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.

Reconnect the Battery Cable
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”
As usual... Tim is right. This is the proper method. It works on OBD jeeps (pre-96).

I had a O2 sensor CEL (flash code 21). I replaced the O2 sensor, removed the battery cables for about 15 minutes, and started the Jeep, just to test. The CEL remained. I did the exact method Tim outlined, and the code cleared, and in 500 miles hasn't come back, because with the new sensor it never re-tripped. For some, it seems that removing the battery cables works, I'm curious though if they've done this, or they're putting out bad information.

If you've got decent condition grounding straps, simply removing both cables from the battery, and holding them together will work. The key on & one cycle of the light switch. I have a newish 2AWG cable from my block to my negative battery post though...

Merry Christmas all...


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post #13 of 18 Old 05-03-2011, 08:11 PM
Mark Beer
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Tim's method does not work on my '95 Sport with the new pcm in. however, if I put the old pcm back in and run that method again, it will run ok.

I've even tried the neg cable to pos terminal for 5 minutes trick, but no bueno either.
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post #14 of 18 Old 05-03-2011, 09:18 PM
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post #15 of 18 Old 09-10-2013, 08:48 AM
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For what its worth (and it IS worth $$); I used the 30 sec ground followed by key ON, LIGHTS ON & OFF; WALAA!! Done

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