99 EB 5.4 intermittent shut down issues

[tekrsq]

Ok...I've been having intermittent issues with the truck suddenly shutting off at stoplights. It idles fine, then just shuts off for no reason. When it shuts off, it will crank & crank, but not start, and has a rapidly blinking theft light, and dashes across the odometer. After sitting for a couple of hours, it will restart.

I originally thought this was an issue with my SCT controller because I didn't have this issue until there was an error while changing tunes on the truck. While troubleshotting that issue, I found out my alternator was not charging at idle (again..intermittent), and was killing the battery. Both were replaced, and I had not any issues for a couple of weeks..until last night.

So, after a ton more research, I have found the possibility it could be either a bad PCM relay, or PCM diode. The relay is easy enough to find, but I cannot find the diode ANYWHERE. The diode in my truck is F57B-14A604-A. All I can find is diode F5TZ-14A604-A. Are they the same diode....just updated with a new number ?? If not, any idea what I can use in place of my original diode ??

 

[Duane Wong]

I changed the pcm, had the instrument cluster soldered to allow the odometer to always display by glowing numbers and symbols, changed the GEM but I still get a random shutdown at various speeds accompanied by ------- on the odometer and 0 RPMs after it shuts down. I can simulate the ------- by removing the relay for the PCM, but, that does not explain why when I attempt to restart the car, it always starts up and runs fine immediately.
I was told that the communication problem may be caused by a broken wire, a broken insulator in a wire, or a lack of power from the relay to the pcm, which is situated on opposite sides of the engine compartment connected by wires. K&D Auto Electric in Somerset, PA 15501 says that if I get stuck and it won't start at all that it will be easier to diagnose. I have exhausted all possible causes in my experience and theoretical knowledge of driveability issues, except finding a shop that can chase all the relevant color coded wires through the harness to find where the break or short to ground is.

I forgot to mention, that it happens more frequently when it is raining and I am driving it, pointing to a shorted wire, or a bad sensor reading.

Before it shuts down, sometimes the speedometer and odometer needles go crazy maxing out at max values, then going to minimum values. It really behaves like the Millenium Falcon, only banging on the electronics doesnt seem to help. LOL.


Duane Wong
Somerset, PA
1999 Ford Expedition 198,000 or so miles.

 

[tekrsq]

I changed the pcm, had the instrument cluster soldered to allow the odometer to always display by glowing numbers and symbols, changed the GEM but I still get a random shutdown at various speeds accompanied by ------- on the odometer and 0 RPMs after it shuts down. I can simulate the ------- by removing the relay for the PCM, but, that does not explain why when I attempt to restart the car, it always starts up and runs fine immediately.
I was told that the communication problem may be caused by a broken wire, a broken insulator in a wire, or a lack of power from the relay to the pcm, which is situated on opposite sides of the engine compartment connected by wires. K&D Auto Electric in Somerset, PA 15501 says that if I get stuck and it won't start at all that it will be easier to diagnose. I have exhausted all possible causes in my experience and theoretical knowledge of driveability issues, except finding a shop that can chase all the relevant color coded wires through the harness to find where the break or short to ground is.

I forgot to mention, that it happens more frequently when it is raining and I am driving it, pointing to a shorted wire, or a bad sensor reading.

Before it shuts down, sometimes the speedometer and odometer needles go crazy maxing out at max values, then going to minimum values. It really behaves like the Millenium Falcon, only banging on the electronics doesnt seem to help. LOL.


Duane Wong
Somerset, PA
1999 Ford Expedition 198,000 or so miles.

Yeah, intermittent issues are a serious pain in the ass to diagnose. Because your issue is more prevalent when it rains, I would SERIOUSLY be looking at a windshield leak. They are VERY WELL KNOWN for leaking windshields, and yours sounds exactly like water leaking into the PCM.

Although, I have had my issues when it rains, I've also had them when it's been sunny. I'm not totally ruling out a windshield leak yet, although there is no evidence I can see under the dash. For now, I have replaced both the PCM relay and the PCM diode. No issues since changing them, but there has not been a heavy rain yet either. If the issue continues, I'm at my next to last resort, and will just replace the windshield. My last resort will be to replace the PCM.

 

[tekrsq]

I thought I updated this thread as SOLVED. I ended up finding a new PCM diode and PCM relay and replaced them both. I have not had the issue since replacing them.