Electrical O'rileys And I Are New Best Friends!

Discussion in 'SN95 4.6L Mustang Tech' started by SiahNyde, Mar 18, 2014.

  1. ...I would be taking it back to this shop and demanding that they fix it. The problem arose after they replaced your PCM because it didn't communicate with "their" software? It sounds to me like they introduced the problem to your cars electrical/computer system.
    trombonedemon likes this.
  2. Well here we are...Several months later...Ended up taking the car to Ford, and long story short, PCM had a bad ground. After I replaced the PCM the car has not had a single problem as far as CCRM/dashboard issues however, the fuel pumps no longer prime and the car cranks but won't start. Am I correct in assuming that this would be a result of the PATS system?

  3. You took it to Ford and they identified a bad ground on the PCM...

    Did you then DRIVE the car home?

    I having difficulty figuring out what happened between:


  4. Negative. Not likely a PATS problem. In the 1996+ model year PATS does not with hold power to the fuel pump. It works by with holding fuel injector pulse. Even if PATS has been activated, the fuel pump MUST prime on initial key on.

    If the fuel pump is not priming on initial key on, start by confirming +12 volts at the trunk mounted IFS switch.

    IF no power at the IFS switch the problem is upstream towards the CCRM, fuse, ignition switch.

    IF power at the IFS switch, then the problem is down stream, Fuel pump, FPDM, PCM, or fuel pump ground.

    It might help others if you explained where the bad ground was and how it was found.
    #24 wmburns, Aug 4, 2014
    Last edited: Aug 5, 2014
  5. Sorry for the confusion...I'm having a hard time describing the issue because it's so periodic, and sometimes the car will start up and run like nothing is wrong, then other times I can spend several minutes cranking the car over without it starting.

    When the latter happens, the issue of clicking and the other symptoms I described are present.

    After I dropped it off at Ford and described to them the problems I was having(clicking sound, car cranks won't start/fuel pumps prime fine), They determined that there was a bad ground from the PCM to the CCRM. I purchased a new PCM, installed the chip that has my tune on it, and the car has not shown a hint of the initial problem, although it does not fire up now.

    The only thing that has changed since the last time I drove the car home from the shop is a new PCM. I was assuming that the car not starting would have to do with the PATS system since the fuel pumps not priming had never been present until a new PCM.

    I am unaware of how the bad ground was found, but Ford diagnosed my car and discovered a bad ground from the PCM to the CCRM...They said it was why the clicking sound was present and the car was exhibiting the symptoms of a bad CCRM...