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05 Liberty PCM issues, or so I think.

centermass556centermass556 Senior MemberPosts: 3,534 Senior Member
So,

Looking back, I think it started a while ago. The Jeep would run like crap then run fine. I would have a week of crappy gas milage and then get what I should. I chalked this stuff up to cold weather and traffic. Then yesterday I began having issues with the Instrument panel. While driving the engine would get rough, the instrument panel would go bonkers (warning lights flashing on and off, gages jumping all over) and then it would stall out. I did some quick google-fu searching. Unhooked the negative battery cable and let it sit for 30 minutes. Reconnected the battery cable, cranked it, and the jeep ran great....for about 10 miles and then it started again. The code from the CEL is U0155.

I guess my question is, IS there a sure fire to ensure it is the PCM and not something else.
"To have really lived, you must have almost died. To those who have fought for it, freedom has a flavor the protected will never know."

Replies

  • olesniperolesniper Senior Member Posts: 3,767 Senior Member
    Little over a year ago, my Patriot started acting wonky. Be running fine, then the EMC light , on the dash, would come on and it would start running real rough. Be driving down the road, in cruise control, start up a hill and it would surge suddenly. Sometimes, you could pull over, shut it off, and wait a couple of minutes and it would run fine, maybe for a half hour , maybe for 5 minutes. Dealer found some sort of modular, on the bottom of the throttle body that had a stripped plastic gear in it. They said the EMC was trying to compensate for it not working , causing it to run rough, surge , and throw out weird engine codes. I have a B to B aftermarket warranty, so they replaced the entire throttle body. Bill was $400+, parts and labor. I paid $100.
    Yea, though I walk through the valley of the shadow of death,
    I will fear no evil: For I carry a .308 and not a .270
  • tennmiketennmike Senior Member Posts: 27,457 Senior Member
    olesniper wrote: »
    Little over a year ago, my Patriot started acting wonky. Be running fine, then the EMC light , on the dash, would come on and it would start running real rough. Be driving down the road, in cruise control, start up a hill and it would surge suddenly. Sometimes, you could pull over, shut it off, and wait a couple of minutes and it would run fine, maybe for a half hour , maybe for 5 minutes. Dealer found some sort of modular, on the bottom of the throttle body that had a stripped plastic gear in it. They said the EMC was trying to compensate for it not working , causing it to run rough, surge , and throw out weird engine codes. I have a B to B aftermarket warranty, so they replaced the entire throttle body. Bill was $400+, parts and labor. I paid $100.

    Engineers must be smoking, eating, snorting, and shooting crack simultaneously now. Why would any engineer with the intelligence of a **** amoeba put plastic parts on an engine where the engine gets HOT? Granted, there are some plastics that will work in high heat environments, but they don't get used too much in consumer stuff; too expen$$$$ive. Injection molded pot metal is just as easy to make as injection molded plastic and will at least stand the heat.

    I guess the automotive engineers now don't study heat flow anymore. :tooth:
      I refuse to answer that question on the grounds that I don't know the answer”
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  • TeachTeach Senior Member Posts: 18,428 Senior Member
    Automotive PCM's live by the same rules as any other computer- - - - -GIGO. Give it the wrong information, and it spits out the wrong results. Things like throttle position, intake manifold vacuum, coolant temperature, atmospheric pressure, mass airflow, etc. can all conspire to give the control unit bad data. Intermittent problems are the absolute worst ones to find- - - -I built a pretty successful career diagnosing problems other guys would give up on Check out all the wire harness connections for looseness or corrosion and if possible, have someone run a diagnosis with a scan tool that allows you to monitor individual signal voltages instead of just reading trouble codes. The code is just a signpost pointing to which system or circuit needs a more in-depth diagnostic procedure. Good luck!
    Jerry
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