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Old June 6th, 2020, 20:30
Xj98Classic Xj98Classic is offline
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Exclamation Replacing ECM programming?

I just bought a 98 cherokee 4wd 4.0 automatic.
Guy sold it because it was misfiring, stalling, and stuttering.

I bought it and tried to figure the problem out. What I found was when
I touch the harness for the ECM it would die. I found a messed up wire
and fixed the wire.

It would still stutter and miss and randomly cut out.
I hit the ecm with my hand and it died. Wouldn't start after. I hit it again
and it started. I squeeze it and it dies.

I figure it was a faulty ecm. I went to a junk yard and pulled one from an
identical jeep, year engine and trans. It was a different shape ecm but I
checked 2 different identical jeeps to mine (maybe not trim level) and they both have different than what was in mine.

I bought one installed it. The car starts and instantly dies. If I rev it it will rev barely stay on and die when I stop.

Am I missing something? Do these ecms need programmed to the car Vin?
I read online about vtss? How would I know if my car has it?

Any info would help. Its hard to find on Google.
Thanks guys.
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Old June 7th, 2020, 09:55
lawsoncl lawsoncl is offline
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Location: North Idaho
Posts: 5,250
Re: Replacing ECM programming?

What's the part number on your original ECM? Can you post pictures of the different shape? As far as I know the shape of the ECM didn't change from like 1996 to 2001. Dying after 2-seconds does sound like a skim/vtss issue.

Doesn't the CA emissions test check the VIN in the computer against the vehicle? The variations in programming would be 4-cyl/6-cyl, auto or manual, and CARB or Federal emissions.
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Old June 7th, 2020, 10:18
Xj98Classic Xj98Classic is offline
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Re: Replacing ECM programming?

The junk yard ones are boxy. The one that was in it is a rounded corner box with fold tabs that hold a cover on. Inside is a solidified jelly.
Someone else has told me the rounded one is a refurbished one and the boxy one is a factory one.
This was their response.

The symptoms are not SKIM related. The old PCM looks like a refurbished unit. The junkyard PCM is for 1998, is Calif emissions, but should work.

It is very likely that the PCM has re-booted and deleted the idle settings from sitting with no battery. Go for a test drive to restore the idle settings. You will very likely have to start out with one foot on the gas pedal to keep the engine running, and the other foot on the brakes.

The new For 1996+ Jeeps, the OBD-II engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator is not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM or poor battery charging. Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem. A faulty Coolant Temperature Sensor may also cause similar symptoms. Testing of the CTS is recommended as part of the diagnostics. A poor ground at the ignition coil can also cause similar symptoms.

The reboot symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. (3) The ECU will relearn the idle settings after a short period of driving and the engine should start and idle normally.
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Old June 7th, 2020, 10:19
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devildog0 devildog0 is offline
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Location: Hunt County Texas
Posts: 841
Re: Replacing ECM programming?

Post photos of these different ECMs.
1995 XJ Country/4.0L/AW4/231/UpCountry Suspension
2004 Suzuki DL650 VStrom/1978 Suzuki GS1000E/2003 Yamaha TW200
1982 Suzuki GS850G (barnfind project)
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Old June 7th, 2020, 10:50
Xj98Classic Xj98Classic is offline
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Re: Replacing ECM programming?

Having trouble posting a picture. This is a link to the two different styles.
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Old June 7th, 2020, 10:52
Xj98Classic Xj98Classic is offline
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Re: Replacing ECM programming?

Part number on the router did one is no longer readable. Sticker is destroyed.
Part number on junk yard one is. 537 AH
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