ECM replacement. Weird.

Discussion in 'How To' started by Bill chase, May 22, 2019.

  1. Bill chase

    Bill chase New Member

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    I had the wire clips around the front driveshaft let go, burned through the heater circuit for downstream o2 bank 1, went to replace sensors, figuring the car has 185k on odometer and they are original sensors. This is where it gets weird..

    Upon replacing the sensor i find the shorted wires, check everything out, grounds good, heater control circuit good, reference voltage good.. so i elect to not change the sensors, just fix the bare wires and reattach the clips with zipties. Reset codes, all is well for a few days. Then the light comes back on, engine starts running erratic, p0300, p0037, P0038, p0132 and p0152. Trouble shoot with Chrysler manual as much as i can without scan tool, now i have no heater control voltage to sensors, or at ecm pin 32 or 39 i believe, take to a trusted shop with scan tool and he confirms my suspicion ecm needs replaced. He followed chryslers manual just as i did, as well as checking the major splices for power and ground in these circuits. And also concluded the ecm is dead.

    I drove the car maybe 75 miles after the light came on, and fixed it as soon as i could.. and now i have all these codes, as well as occasional erratic running. I guess i cant believe Chrysler didnt put some type of fuse in the o2 heater circuit, anyone ever have this happen? I change the cheap copper plugs every 35k weather they need it or not, run midgrade every 3rd tank and am the 2nd owner, the car has ran great for 5 years.. i am just amazed such a small 14 guage wire with basically no amperage being shorted could kill the ecm like this

    But my real issue is, for all these codes its throwing it actually runs ok, aside from having bad fuel economy.. when ordering a replacement ecm and having it flashed to my vin.. do i have to have the mileage match?? I mean id like to keep driving the car until the new part arrives, knowing it could die completely at any time it is my only means of transportation and i hate to burn up vacation days over this. So if i order it and mileage is say 100k and by the time i install it the mileage is 100,150 is it going to cause me problems?? They all ask for vin as well as mileage is why i ask.. anybody??
     
  2. Bill chase

    Bill chase New Member

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    2006 renegade 3.7 auto 4x4 by the way.

    Ecm part number is p05094939ad
     
  3. Bill chase

    Bill chase New Member

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    Can i grab exact same ECM part number feom salvage yard?? Local u pull has 3 2006 renegades emmisions same, 2 have same software update label on ecm
     
  4. Billwill

    Billwill Full Access Member

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    Actually a PCM on the gasser and an ECM on the Diesel but you have stated that you have gasser so no problem!

    If the PN on the PCM is the same it will work....last two characters are the revision level..the higher the better!

    The PCM/ECM is generally a robust item but shorts to ground could blow something inside it.

    Do you have the wiring diagrams?

    Download your year KJ here at www.colorado4wheel.com/manuals/Jeep/KJ

    Section 8W has the wiring diagrams.

    Other sections tell you what to do about the CEL codes.

    I have over the last few years had to replace 9 faulty wires on my 2002 Export 2.5 CRD due to a front end impact that damaged the harness up front...some wires broken or shorting to ground but some wires shorting to some other random wire next to it in the harness.

    Just a few days ago I had to replace a wire going from the MAP sensor to the ECM....this time at the rear of the engine and not caused by the frontal impact but the Lady is getting a bit old now!:(
     
    Last edited: May 24, 2019
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  5. Bill chase

    Bill chase New Member

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    Follow up, the short did kill the computer, replaced it and all codes went away.