PCM (ECU) Fast Learn Mode

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Comanche91
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Joined: February 13th, 2008, 4:51 pm
Stroker Displacement: 4.6L
Vehicle Year: 1991
Vehicle Make: JeeP
Vehicle Model: Comanche
Location: Sweet Home Alabama

PCM (ECU) Fast Learn Mode

Post by Comanche91 »

Quick question regarding erasing existing ECU memory to allow a new “Adaptive Memory” to be developed. I've made quite a few changes lately and the stroker is running like crap as it always does when power is disconnected from the ECU until driving 200-300 miles or so while it re-learns" it's new settings. My question is I know the below procedure works fine on ODBII systems, but will it also work on 91-95 OBDI systems as well?

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”
91 Comanche LWB, AW4, Hesco 4.6L, D44 Trac-lok, CHROME freak, ROLL TIDE
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SilverXJ
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Stroker Displacement: 4.6L
Vehicle Year: 2000
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Radford, Va

Re: PCM (ECU) Fast Learn Mode

Post by SilverXJ »

Touching the positive to ground will suffice to drain the capacitors. I've seen that headlight method before and I don't understand the reasoning behind the headlights on the XJ(or MJ in your case). They aren't linked to the PCM nor is there a BCM linked to the PCM.
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Comanche91
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Posts: 156
Joined: February 13th, 2008, 4:51 pm
Stroker Displacement: 4.6L
Vehicle Year: 1991
Vehicle Make: JeeP
Vehicle Model: Comanche
Location: Sweet Home Alabama

Re: PCM (ECU) Fast Learn Mode

Post by Comanche91 »

Turning the headlights on then off; after erasing volatile memory, the computer senses this as a trigger to return PCM nonvolatile memory to default, or factory new, in quick learn mode.
Thus, with volatile memory gone due to no power and nonvolatile memory reset to default, the computer is blank as far as stored adaptive memory. Clean and new and ready to record.
Image Maybe this applies to just TJs and YJs. I'll try this tomorrow and see what, if anything, happens. I've just started the "re-learning" process after removing the Unichip and rewiring the ECU harness last week.
91 Comanche LWB, AW4, Hesco 4.6L, D44 Trac-lok, CHROME freak, ROLL TIDE
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