Ccrm Issue

Discussion in 'SN95 4.6L Mustang Tech' started by onefaststang, Apr 12, 2014.

  1. For the 1996-1997 model year there is an end user procedure documented in the Ford service manual to re-program PATS. The procedure takes 45 minutes to perform and each step must be performed exactly.

    The procedure is not in a format that can be posted. If interested in getting a copy of the service manual & wiring diagrams for yourself I may be able to help. PM if interested.

    I personally do not recommend PCM replacement as a trouble shooting tool. Likely to create as many problems as it solves. At the minimum perform a visual inspection of the PC board looking for burnt components.

    The wiring diagrams will also help should you decide to "ring out" the signal return lines. Includes connector pin out with wire colors. If this is within your skill set I highly recommend. It could save the work of PCM replacement only to find the new PCM has the same problem. At the very least, this could offer greater confidence that a PCM replacement is worth the effort.
  2. Absolutely. Pm coming your way.
  3. Pulled the pcm and opened it up. Can't find anything. No burn marks, no loose soldier joints. Looks like I'm pulling the loom off and tracing some wires.
  4. Put the power probe to the connector at the coil. I have power to the center pin but it is not 100% constant. It flashes. The 2 outside pins also have power, but it drops every few seconds. I have video, but no way to post it.
  5. After putting the ecm back in I hadn't had any problems for a few days. Got daring and decided to take it to work this morning. On the way down the highway it started to miss again. It lasted for about a 1/4 mile, then cleared up. My wideband showed the a/f lean @ 18:1. That's as high as the gauge goes. If I was just losing spark I would think it would go rich instead of lean.

    I know I am losing spark because I can pull the wire from the coil and get no arcing. Does the ecm pull spark if there is no fuel? Maybe I am having an injector issue.
  6. Are the any DTC codes?

    In the absence of DTC codes, how would be the PCM "know" that an injector isn't firing? The answer is it doesn't. The only indication the PCM has is the misfire itself.

    Any injector failure that the PCM can detect will also throw a DTC code.

    What have you done to rule out excessive dwell as the cause of your issues? You are aware that excessive dwell will burn up a coil? In some cases it could cause an engine fire.

    In one of your previous post it looks like you tried to perform a "noid" test. However, with out detailed descriptions of "how" the test was done on the result by wire color, it's too hard for me to figure out.

    But I can tell you with absolute certainty the dropping power to the coil pack is NOT good. There MUST be +VPWR power all of the time the key is on to the coil pack. BUT... what are you using for the ground? This could give bad results if not using a known good ground to test power.
    #26 wmburns, May 27, 2014
    Last edited: May 28, 2014
  7. No codes.

    How do I test for excessive dwell?

    I can email the video of my test, but have no way to post it here. Power probe grounded direct to battery.

    Also have new 1/0 welding cable grounds from battery to engine, engine to frame.
  8. When I was worried that my ECU was toast, I sent it out for testing. Took about a week before I got it back, they tested the hell out of it and confirmed my ECU to be good. I can send you the contact info it you want. The price was fair and they were really nice guys.
  9. One way to test for excessive dwell is to use a "noid" test light across the low voltage side of the coil. The testing points to be the signal return lines and a known good ground. The light will blink as the PCM "fires" the coil. What you are looking for is for the light to stay off for an extended length of time. Also note if the pattern is not even.
  10. Can I use a standard test light to do this? From all the actual noid test kits I have looked at, nothing is made for that specific application.
  11. I wasn't sure if it would be ok to post a link to their website or not. I'll PM it to you.
  12. Ok. Got myself a noid light set. Put it in line with #8 plug wire. I then grounded my test light and probed the side of the coil plug the goes to that cylinder. After probing for a few seconds it seems to drop a cylinder or 2. There is still action at the noid light though. The flash seems slightly less frequent but not much.
    Remove the probe from the coil and after a few seconds it picks back up again.
  13. The "noid" testing needs to be done on the LOW voltage side of the coil pack. The noid tester isn't designed to test high voltage applications such as on the spark plug wires.
  14. This was on the low voltage side