Unwarranted Error Codes or "Check Engine" light

This operation was first performed by a TJ owner, who verified its existence with a jeep engineer (anonymous). I performed this same sequence last night to reset my brand new Power Control Module, after having altered the vacuum lines. This write-up is paraphrased from that TJ owner:

PCM Fast Learn Mode

I think most people know that the PCM performs several functions controlling Air Fuel ratios via Injector Pulse Width and Ignition Timing.

These “outputs” are controlled using the “inputs” received from all the sensors and then comparing these reading against a set of data tables burned into the PCM. These “memory tables” are the brains that keep the engine running at low emissions and peak economy across the RPM band

What most people don’t know is that these memory tables change. They are “adaptive”, based on sensor readings, driving habits, engine performance and sensor tolerances. Over time, the PCM Memory Tables become tuned to your engine.

Most folks know that disconnecting the battery for 15 to 20 minutes will reset the PCM to get rid of a Check Engine Light or Error Codes stored in the PCM. However this DOES NOT reset the Adaptive Memory Tables in the PCM. Until recently I did not know how to do this.

What you will need
1. Wrench set to remove battery cable (my sizes are different now, but I believe most require 10mm)

How To

Forced Flash

This very simple procedure will Erase the “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.

1. Disconnect the POSITIVE battery Terminal and touch it to ground for 30 seconds. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory)
2. Reconnect the Battery Cable
3. Turn Ignition Switch to the “On” position but DO NOT start the engine
4. Turn Headlight “On”
5. Turn Headlights “Off”
6. Turn Ignition Key “Off”

Adaptive memory has now been flashed, or erased from the PCM. When you start the engine it will be running off a set of pre-programmed tables that come with the PCM from the factory. When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory.”

The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.

Warm-up Cycle

A warm-up cycle happens when all of the following conditions exist.

1. Engine is running
2. A raise of 40F in engine temperature must occur ABOVE the engine temperature at start-up
3. Engine Coolant Temp must reach at least 160 F.

Once your engine has gone through 50 warm-up cycles in at least a 500-mile distance the PCM adaptive memory is set. It WILL NOT Change unless you flash it out and start all over again. This procedure is vitally important for any mods you make to your engine that will alter its performance.

You best performance will happen when the Adaptive memory is set to the current conditions of your engine. The TJ owner tested this on the Dyno and found that, over many miles and having a "broken in" vehicle, running on the original adaptive memory settings had gradually cost him a total of 9 HP and 17 ft/lbs of torque.

While this was only one test it certainly is an indicator to me of the importance of having the “Adaptive Memory” inside the PCM controlling the engine outputs based on the most current engine condition and not those set by the factory or those set in Adaptive Memory 83K miles ago.

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Tucson, AZ
2008 Jeep Wrangler Unlimited (JK)

Does the same process work for all Jeeps, Dodges, and Chryslers? My brother has a Neon and I want to know if it will work on his car too.

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04 KJ Sport
K&N RF-1027
245/75/16 Kumho Road Venture KL-78 on Limited wheels

Down Right L.O.S.T. Florida #223221
http://www.cardomain.com/ride/2224536

I know this is an old thread but I was wondering if anyone tried this??

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05 BLACK KJ - 42RLE & NP242
Skids, Hooks, Bent Rock Rail, Lifted, A/T's, etc.
NY and PA and Florida ONF Special Custom Organic Trail Rash

This is another intresting thread that I never saw. I wonder how many people tryed this. I have never seen any comments about doing this or ever heard it in any convo

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2003 KJ Sport JEEPZILLA Edition
American Flag flying high
Frankenlift removed =(
Moabs and plenty of pin striping
Flexable people don't get bent out of shape!
Current MPG 6" to a gallon
L.O.S.T. # BL065211
www.ItAtYourHome.com

I know this thread goes back a ways but anyone try it? I've got a P0300 code (multiple cylinder misfire) that was an issue over the summer. I changed all the spark plugs and it went away (old spark plugs all seemed fine - nothing that stood out.) Now after about 8,000 miles on the plugs I've got the P0300 code again. I'd also like to know if doing this will erase things like a transmission flash that the dealer did a while back?

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(Formerly just “scoobysnax”) '04 Liberty Limited - 245/70/16 Firestone Destination AT's, Mopar tow hooks, Draw-Tite Class IV hitch, Skid Row Engine & Transmission Skids, Mopar T-Case & Gas Tank Skids, Extended Breather Tubes, Red Top Optima, Sylvania Silver Star head lights, Hella 500FF bumper mounted driving lights

The above is not a "flash" or anything else,it just erases the RAM in the PCM/TCM/BCM forcing them to "re-learn" your driving habits.A true "flash" is software updates that will not erase until written over by a new "flash".

Just simply unhooking the battery,even for a few seconds does the same thing.The extra turning the headlights on/off is to drain the capicitors in the SRS control module,the PCM/TCM/BCM does not have any internal stored power like the SRS control module does.

Some hard OBDII codes will not be erased by unhooking the battery even though the MIL light is off.Actually by unhooking the battery you will get a OBDII code but it will not turn on the MIL light.I believe that code is P1682 or something like that which is "battery disconnected",well duh!!!!