I'd get a junkyard ECM before I would get a new aftermarket one.
New PCM, Car worked for month, now dead again
- Thread starter TallPaul
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Originally Posted By: zzyzzx
I'd get a junkyard ECM before I would get a new aftermarket one.
According to these folks that would be a bad idea. They say that the Ford ECMs through 1999 are prone to failure after about 10 years or so many miles so your junkyard ECM will have a lot of years and miles already on it.
The used one my shop put on the Aerostar was only to test if it worked, they bought an ECM from the parts store and I think they went with O'Reilly. Hopefully the next one will last.
Originally Posted By: punisher
Ford assumes owners are stupid. Sometimes jumper cables get hooked up backwards- ECMs have diodes on their power inputs just for this. Voltage spikes happen, like from cheap non spec starter solenoids, alternator diodes fail (AC voltage output), but nothing that will kill an ECM.
Well that is good news, though the site I just linked above says of Ford OBD-1 (1990-1994), that components such as the ECS, the ISC, TPS, engine sensor, alternator or failing batteries can adversely affect the PCM, and that reverse hookup on a battery jump can damage the ECM.
I'd get a junkyard ECM before I would get a new aftermarket one.
According to these folks that would be a bad idea. They say that the Ford ECMs through 1999 are prone to failure after about 10 years or so many miles so your junkyard ECM will have a lot of years and miles already on it.
The used one my shop put on the Aerostar was only to test if it worked, they bought an ECM from the parts store and I think they went with O'Reilly. Hopefully the next one will last.
Originally Posted By: punisher
Ford assumes owners are stupid. Sometimes jumper cables get hooked up backwards- ECMs have diodes on their power inputs just for this. Voltage spikes happen, like from cheap non spec starter solenoids, alternator diodes fail (AC voltage output), but nothing that will kill an ECM.
Well that is good news, though the site I just linked above says of Ford OBD-1 (1990-1994), that components such as the ECS, the ISC, TPS, engine sensor, alternator or failing batteries can adversely affect the PCM, and that reverse hookup on a battery jump can damage the ECM.
If the caps are failing, pop 'er open and replace them.
Done|
Done|
Originally Posted By: punisher
Yup. No way for it to be an ECM relay.
Ford ECMs are tough, seriously tough. I replaced three of them, one bad ECM off the transport at the dealership, one due to water intrusion, and one fried due to a lightning strike (which also fried another $3K worth of modules/electronics).
Everything the ECM controls is through grounds. Injectors- ECM grounds each injector individually (SEFI) or by bank. There is not really anything in the wire harness or injectors that can kill all the injector drivers. The fault is internal to the PCM in the logic somewhere. Could be a bad cap or just some microprocessor that decided to give up the ghost.
Ford assumes owners are stupid. Sometimes jumper cables get hooked up backwards- ECMs have diodes on their power inputs just for this. Voltage spikes happen, like from cheap non spec starter solenoids, alternator diodes fail (AC voltage output), but nothing that will kill an ECM.
More than likely the rebuilt ECM was garbage. When I was an independent we replaced our share of GM ECMs and sometimes we went through two replacements until we got one that worked properly. There are rebuilders that do very shoddy work. We learned fast to grab our ECM/PCMs from NAPA at that time.
We seem to replace a lot of PCMs lately. I don't know what it is, when they get called back they go to Visteon like the old ones, so I wonder if there is a different initial vendor and Visteon does the service replacements. I was always under the impression that the Ford ones were bullet proof unless people messed with them.
On the older rides where we have to get reman PCMs we usually have to go through 2 or 3 to get a good one.
Yup. No way for it to be an ECM relay.
Ford ECMs are tough, seriously tough. I replaced three of them, one bad ECM off the transport at the dealership, one due to water intrusion, and one fried due to a lightning strike (which also fried another $3K worth of modules/electronics).
Everything the ECM controls is through grounds. Injectors- ECM grounds each injector individually (SEFI) or by bank. There is not really anything in the wire harness or injectors that can kill all the injector drivers. The fault is internal to the PCM in the logic somewhere. Could be a bad cap or just some microprocessor that decided to give up the ghost.
Ford assumes owners are stupid. Sometimes jumper cables get hooked up backwards- ECMs have diodes on their power inputs just for this. Voltage spikes happen, like from cheap non spec starter solenoids, alternator diodes fail (AC voltage output), but nothing that will kill an ECM.
More than likely the rebuilt ECM was garbage. When I was an independent we replaced our share of GM ECMs and sometimes we went through two replacements until we got one that worked properly. There are rebuilders that do very shoddy work. We learned fast to grab our ECM/PCMs from NAPA at that time.
We seem to replace a lot of PCMs lately. I don't know what it is, when they get called back they go to Visteon like the old ones, so I wonder if there is a different initial vendor and Visteon does the service replacements. I was always under the impression that the Ford ones were bullet proof unless people messed with them.
On the older rides where we have to get reman PCMs we usually have to go through 2 or 3 to get a good one.
Basically older Ford ECM are mostly fine(the same cannot be said for many other mfgrs), other than the OBD-1 F-150 units I don't know of any that have a regular pattern of failure...
I've seen two failed OBD-1 units that were the result of arcing the alt battery cable to ground but as far as bad sensors, over charging alt, etc it rarely happens... A overcharging alt that kills ECM is likely going to boil the battery dry and blow lights long before the PCM...
I'm running a '89 Mustang ECM in my 5.0 converted T-Bird and it's been in a saltwater flood(ECM not car)... I washed it out with water followed by alcohol something like 10 years ago and it's had no issues...
I've seen two failed OBD-1 units that were the result of arcing the alt battery cable to ground but as far as bad sensors, over charging alt, etc it rarely happens... A overcharging alt that kills ECM is likely going to boil the battery dry and blow lights long before the PCM...
I'm running a '89 Mustang ECM in my 5.0 converted T-Bird and it's been in a saltwater flood(ECM not car)... I washed it out with water followed by alcohol something like 10 years ago and it's had no issues...
Replacement PCM is in, van is running, we'll see what happens next. Hopefully this thread is done for good.
Put a new starter solenoid in just for insurance. It says right on the side a warning that wrong part can damage ECM. I put in another Motorcraft and it also has same warning. Nice O'Reilly has Motorcraft.
Any way to test the old one, see if the diode is bad? just curious.
Any way to test the old one, see if the diode is bad? just curious.
It might be a zener, and I don't know the bias current.
You might try ohming the metal mounting tab (ground) to all of the terminals (mainly S terminal and big power input stud), then reverse the leads and see what changes.
Quickie Bill Nye moment: In a DC circuit every solenoid can act like a little ignition coil. This means everytime a solenoid is turned off, you can get 250-300V of back EMF induced in your 12V primary. Every relay on a Ford has an internal diode, if it is OEM spec.
You might try ohming the metal mounting tab (ground) to all of the terminals (mainly S terminal and big power input stud), then reverse the leads and see what changes.
Quickie Bill Nye moment: In a DC circuit every solenoid can act like a little ignition coil. This means everytime a solenoid is turned off, you can get 250-300V of back EMF induced in your 12V primary. Every relay on a Ford has an internal diode, if it is OEM spec.
I had what punisher is talking about happen to my motorcycle when I replaced a relay.
The stock relay had an internal diode that the new one did not and the bike would not start some times after i shut it off. I wired a diode on the outside and all was well.
The stock relay had an internal diode that the new one did not and the bike would not start some times after i shut it off. I wired a diode on the outside and all was well.
Originally Posted By: TallPaul
Originally Posted By: zzyzzx
I'd get a junkyard ECM before I would get a new aftermarket one.
According to these folks that would be a bad idea. They say that the Ford ECMs through 1999 are prone to failure after about 10 years or so many miles so your junkyard ECM will have a lot of years and miles already on it.
Over on FEOA.net (Ford Escort website) they seem to never go bad.
Originally Posted By: zzyzzx
I'd get a junkyard ECM before I would get a new aftermarket one.
According to these folks that would be a bad idea. They say that the Ford ECMs through 1999 are prone to failure after about 10 years or so many miles so your junkyard ECM will have a lot of years and miles already on it.
Over on FEOA.net (Ford Escort website) they seem to never go bad.
I've never heard of a ford PCM going bad. Chryslers of that era, yes. But rarely a Ford PCM ...
Shedding new light. It dawned on me that some time before the first PCM died, the Aerostar was used to jump another car. The Aerostar was running and in hooking up the dead car, the cables were accidently crossed so that the neg was on the positive and when the positive touched the neg on the dead car, it sparked. That was it, not longer than an instant. So I am thinking that may have done enough damage to the original PCM that it died over the next couple hundered or so miles. As for the replacement PCM, a bad part from the factory or something else was affected in the Aerostar that is going to eat PCMs every 200 miles. Time will tell.
Given that I had two Carter fuel pumps in a row in 2007 and then a Motorcraft that is still working in the Aerostar, I can't say that if the replacement PCMs die twice in a row, that the car is eating them, as then we will go withn a different brand and if it still dies then it must be the van is eating them.
Given that I had two Carter fuel pumps in a row in 2007 and then a Motorcraft that is still working in the Aerostar, I can't say that if the replacement PCMs die twice in a row, that the car is eating them, as then we will go withn a different brand and if it still dies then it must be the van is eating them.
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