Blown88GT
Founding Member
You will never see a few milliseconds dropout, but the computer will. A loose connection might make it appear that the computer is faulty.Error 15 relates to a losing power at pin number 1. Pin number 1 is hot at all times regardless if the ignition switch is on or off. I checked the voltage in wire of pin 1 and it never loses power, that makes me believe the computer is faulty.
Thank you it is really usefulHere's a wiring diagram, if you don't have it.
You are right on that assessment. for now I will try the light bulb and depending on the results I will decide if I will ran a hot wire straigth from the battery to pin No.1 , That way I will find out with absolute certainty. what part is at fault.You will never see a few milliseconds dropout, but the computer will. A loose connection might make it appear that the computer is faulty.
you mean this part here?I think this may have been mentioned but check the ignition switch.
That is correct, I haven’t done that test I took it for a ride today (Sunday) just with the light bulb test light everything was fine but again it started acting even worst because at one point it was just cranking and no starting but smelling raw fuel so I used a spark tester and started cranking and sure enough, no spark! On the next sequence of cranking I saw spark on the tester, I then removed it and fire it up right away.So, if I’m reading it right, you haven’t had a chance to create the new always on power wire to pin 1 test? If the computer replacement test doesn’t improve the results, that would be my next test. Assuming that dedicated wire does the trick, you at least know, somewhere in the wiring that feeds pin 1 that you have a loose connector, pad pin in connector, a damaged wire, a wonky fusible link (that’s what feeds pin 1), etc. Get a Ford wiring book for your car (I/someone may have already mentioned that). Not just the wiring diagrams, the Electrical & Vacuum Trouble Shooting Manual by Ford. I have one and it’s been worth it weight in gold for resolving ECU wiring issues for me. Good luck, you’re getting there.
Thank you for sharing your valuable opinion.One of those ecms is for a stick (A9L) the other (A9P) is for an auto trans.
I feel you are risking damage to the ecu if not matched for your trans.
Send the ecm in to be checked out and be done, you may be trading problems. They are 30 years old and prolly tired.
JMO
You’ve convinced me to proceed with next test on the A9L.Ok, deep breath.
You‘re not at the “swap random parts in and see the downstream results” stage yet. I would concentrate on the potential loss of power issue coming to the ECU over looking for a downstream issue. As I remember, the pin 1 power comes from a fusible link starting on the positive post of the starter solenoid. It’s like Fusable link L. On my TBird, it was a dedicated wire directly to the ECU power relay, then bridged from that connector to pin 1. It’s a black wire with an orange tracer. That relay could be generating a random failure. I don’t suspect the fuel pump relay; doesn’t fit the facts as you‘ve provided them. Also, if the “run” signal was interupted to to ECU, it could demonstrate simular issues.
Swapping the ECU relay is an easy test. LMR has them, probably auto part stores as well, it’s like a $15-$20 part:
The loss of “run” signal is a bit more complicated. You could replace the ignition switch as others have recommended. The run signal, if also failing randomly, would cycle the ECU relay on and off. I believe that would generate the code 15. But so would a wonky ECU relay.
Also, something to consider, as some of us have to, based on how and where are cars are parked: any chance you might have anything chewing on wires? I chased a problem on a 2017 Honda Pilot for 2 months before I realized a mouse had chewed a segment just enough to create a random loss of power. Just another thought to consider.
Hang in there. As I said, I wouldn’t attack the results of the power loss until I’ve run to ground that power into the ECU isn't the problem.
You’re right I will go thru everything in more detail. And since the starter solenoid is tminside the fender I will dive inside of it and very everything is ok.Ignition switch is a known issue in these cars so if you do not know the integrity of it then its not a bad idea to change it out.
You need to verify your wiring. Once you can say the wiring is good then it comes down to relays, ECU's, etc. Start at the starter solenoid at the fusible link and work your way to the ECU relay, over to to the ECU, then work towards the fuel pump relay. Once you know all the wiring it good and have verified the relays then its time to look at the ECU(s). Make sure the ground for the ECU behind the battery is in good shape as this bit me once.
Scroll down to Post #10 in this thread:
engine ground locations
well i broke one ground that goes from the tranny to driverside firewall. putting my engine back together and just trying to make sure i have all grounds hooked up. and are there alternate places to put my grounds? this is my first engine build. need to know where ALL grounds gostangnet.com
I went down under the dash and removed the ignition switch. There was only a ninuscule gap in between the plastic part and the metal bracket, to tighten this little play I pressed on the four fingers and right now is solid I tested the spade terminals with the DMM for resistance/continuity and didn't see and miss contact so I called it good.Ignition switch is a known issue in these cars so if you do not know the integrity of it then its not a bad idea to change it out.
You need to verify your wiring. Once you can say the wiring is good then it comes down to relays, ECU's, etc. Start at the starter solenoid at the fusible link and work your way to the ECU relay, over to to the ECU, then work towards the fuel pump relay. Once you know all the wiring it good and have verified the relays then its time to look at the ECU(s). Make sure the ground for the ECU behind the battery is in good shape as this bit me once.
Scroll down to Post #10 in this thread:
engine ground locations
well i broke one ground that goes from the tranny to driverside firewall. putting my engine back together and just trying to make sure i have all grounds hooked up. and are there alternate places to put my grounds? this is my first engine build. need to know where ALL grounds gostangnet.com
Thanks man! I have to admit that I was so frustrated but I always take my challenges very seriously. I took the computer apart some five times trying to find out a single evidence of a failure but non of the components were visually bad. Took few measurements and tried to find out wher the KAM is stored. The entire EEC board smell nice with no burnt smell.You da man. Congratulations on smartly discovering the problem without becoming the guy who just replaces parts until he replaces the bad one. I’m sure with the knowledge you gained on this fix, you’ll be able to help lots of folks. Again, congratulations!
Mods should make a sticky of this for a nice TFI module tester on ebay.That is correct, I haven’t done that test I took it for a ride today (Sunday) just with the light bulb test light everything was fine but again it started acting even worst because at one point it was just cranking and no starting but smelling raw fuel so I used a spark tester and started cranking and sure enough, no spark! On the next sequence of cranking I saw spark on the tester, I then removed it and fire it up right away.
I thought well maybe the TFI module was the problem or the pick up magnet inside the dist.
I got so frustrated that I installed the other computer but I haven reconnect the battery yet.
I’m not sure if I want to keep dealing with the A9L or try the other one to see if at least code 15 dissapears. That no spark opened a new set of possibilities, but at this point the ignition switch is suspect too…
Thanks man for staying with me, I appreciate it a lot.