Help with weird problem.

[SHOZ123]

Strangest problem I've ever not seen......

 

[Phoenix]

huh wheres the first post?

 

[SHOmaniac1975]

MY post disappeared.

I posted that I was driving along in my 98 SHO, and all of a sudden it sputtered, stuttered, and stalled. all the lights came on except the MIL, and it would not restart. At first I thought it was the cam demon visiting me.

After I got it towed back to my shop I hooked my MAC mentor up to it and got no communication with the ECM. I got a multiplexer error 0001 when I tried going through OBDII generic as well.

I checked all 3 fuses and relays for the PCM, as well as the diode and they were fine. I have no spark and no fuel. Has anyone ever heard of a PCM crashing out of the blue before?

I ordered a PCM from Midnight auto parts on EBAY. Will it need to be re flashed, or the PATS re-programed?

Any help would be appreciated.

Thanks,
Brian

 

[Mr Anonymous]

A '96 or '97 you can just swap the PCM no problem. '98 and '99 you need to have the PATS keys programmed after the swap.

When you turn the key to run, do the fans come on? That's the sign of a dead or non-powered PCM.

First suspect is the PCM power relay which in '96/'97 is in the CCRM, and in '98/'99 is in the engine compartment fuse panel.

You can try jumping power to the PCM to see if it's really dead. Let me know what year and I can tell you what pin to power.

Also, do you have a chip installed? If it became dislodged it can appear as a dead PCM.

 

[TimboSHO]

Let me know what year and I can tell you what pin to power.

I was driving along in my 98 SHO,

 

[bacernate]

check your sensors [maf,cam,crank ,tps etc.]to see if your have your 5 volt reference. if not try unplugging them one at a time to see if one is shorted.

 

[kikkinasphalt]

A '96 or '97 you can just swap the PCM no problem. '98 and '99 you need to have the PATS keys programmed after the swap.

When you turn the key to run, do the fans come on? That's the sign of a dead or non-powered PCM.

First suspect is the PCM power relay which in '96/'97 is in the CCRM, and in '98/'99 is in the engine compartment fuse panel.

You can try jumping power to the PCM to see if it's really dead. Let me know what year and I can tell you what pin to power.

Also, do you have a chip installed? If it became dislodged it can appear as a dead PCM.

PCM wouldnt keep the fuel pump from priming...
if you get NO power to the fuel pump, then its before the pcm.

 

[SHOmaniac1975]

Also, do you have a chip installed? If it became dislodged it can appear as a dead PCM.

I do not have a chip installed. And the fans do not turn on when I turn the key to run. The MIL also does not illuminate when I turn the car to run.
I checked the relays and swapped them with new ones still no luck.
For the PATS reprogram, do I go to Ford?

PCM wouldnt keep the fuel pump from priming...
if you get NO power to the fuel pump, then its before the pcm.

Any suggestions on this one?

check your sensors [maf,cam,crank ,tps etc.]to see if your have your 5 volt reference. if not try unplugging them one at a time to see if one is shorted.

I currently have the PCM removed, does it need to be installed to check for reference voltage?
Sorry for all the questions but Unfortunately electrical diag work is not my strong suit.

Thanks for the help, I really appreciate it.

 

[kikkinasphalt]

you get power at all to the car?
as in will it turn over?

 

[SHOmaniac1975]

you get power at all to the car?
as in will it turn over?

Yes it cranks, lights in dash all light up except MIL light.
Hooked my MAC mentor scan tool up to ODB port and I can not get communication from computer.

 

[Mr Anonymous]

PCM wouldnt keep the fuel pump from priming...
if you get NO power to the fuel pump, then its before the pcm.

WTF are you talking about!?!?

The PCM pulls the fuel pump relay coil to ground to control it. If the PCM doesn't engage the fuel pump relay, the fuel pump doesn't prime, or run, or do anything else. :shakehead

I do not have a chip installed. And the fans do not turn on when I turn the key to run. The MIL also does not illuminate when I turn the car to run.
I checked the relays and swapped them with new ones still no luck.
For the PATS reprogram, do I go to Ford?

I currently have the PCM removed, does it need to be installed to check for reference voltage?
Sorry for all the questions but Unfortunately electrical diag work is not my strong suit.

Thanks for the help, I really appreciate it.

Silly question, but have you checked the bulb for the MIL to make sure it's good?

Yes, you would need to either bring the car to Ford for the PATS re-program or find someone with an NGS.

You need to start by figuring out if the PCM is getting power at pin #'s 71 & 97 with the key in run. You can do this without the PCM installed.

FWIW, if you have access to a "dumb" code reader like an Actron or such, it can often read codes that a more sophisticated scanner can't. It has to do with the way the communicate with the network. The dumb readers don't require a handshake.

 

[kikkinasphalt]

WTF are you talking about!?!?

The PCM pulls the fuel pump relay coil to ground to control it. If the PCM doesn't engage the fuel pump relay, the fuel pump doesn't prime, or run, or do anything else. :shakehead

hrm.
this must be another neat sho thing.. kinda like the batt dying while the car is running if you dont have the cluster plugged in.

ignore me then

 

[SHOmaniac1975]

Silly question, but have you checked the bulb for the MIL to make sure it's good?

Yes, you would need to either bring the car to Ford for the PATS re-program or find someone with an NGS.

You need to start by figuring out if the PCM is getting power at pin #'s 71 & 97 with the key in run. You can do this without the PCM installed.

FWIW, if you have access to a "dumb" code reader like an Actron or such, it can often read codes that a more sophisticated scanner can't. It has to do with the way the communicate with the network. The dumb readers don't require a handshake.

Yeah the MIL bulb works. I always check every time I start the car because of the lovely little surprises this car can bring real fast if ignored.

I reinstalled the PCM and tried my friends Advance Auto Special code reader and still no communication with the PCM.

I ordered a Service CD for the car (which I am going to upload online for everyone on this forum to be able to use once I get it and find a site to host it on) but until it comes I do not know which one is pin 71 and 97. Can you possibly post a picture or drawing of it?, and the procedure for checking them?

If any of you guys are close to Lenox, Ma and have trouble with front end, alignment, struts, brakes etc (Anything but internal motor, transmission and electrical work which are not my forte's)
You can stop by my shop in Lenox and I will help you. I appreciate all the help I have received from the people on this forum.

-Brian


__________________

 

[SHOZ123]

Make sure the PCM relay is getting power and is passing it on. There's a 30A fuse under the hood in the fuse box and the relay is there too.

Make sure there is power on the OBDII port on pin 16. Lower right pin on the connector. There is a 10A fuse under the dash for the data link connector (OBDII port).

Make sure there is 5V power at the TPS.

 

[SHOmaniac1975]

One thing I did notice as well is that the Anti Theft light was blinking really fast while cranking the car when this problem started, after it stalled.

Maybe after I fix this problem I will go Back to a GENII MTX and ditch the GENIII.

The GEN II's were more predictable to deal with, not to mention easier to pull apart and work on...lol

 

[SHOmaniac1975]

Make sure the PCM relay is getting power and is passing it on. There's a 30A fuse under the hood in the fuse box and the relay is there too.

Make sure there is power on the OBDII port on pin 16. Lower right pin on the connector. There is a 10A fuse under the dash for the data link connector (OBDII port).

Make sure there is 5V power at the TPS.

I checked the relay's and fuses, but I have not check power coming from connector from the OBD port. The Pin is on the lower right connector?

If the TPS was not getting power wound I not still be able to communicate with the PCM through the OBD port?

 

[SHOZ123]

If there is not 5v when the key is on at the TPS then there is a problem with the low voltage sensor circuit coming from the regulated PS in the PCM. This could be a wiring issue too as it may be grounded out somewhere.

 

[me6894]

same thing happened when i had my sho it was because there was a water leak and water got into the fuse box... just a thought