Help needed with diagnosis. 20003 Excursion. 7.3L Bone Stock. Daily Driver

Autoenginuity - for analysis

Check Engine - MIL
About every 3 weeks, maybe - hard start.

Codes:
<TABLE cellSpacing=0 cellPadding=3 border=1><TBODY><TR><TD vAlign=top align=middle>P0683 </TD><TD vAlign=top align=middle>— </TD><TD vAlign=top align=middle>GPCM </TD><TD vAlign=top align=left>GPCM glow plug control module communication line failure </TD><TD vAlign=top align=left>Open/shorted circuit, failed GPCM, failed PCM </TD></TR><TR><TD vAlign=top align=middle>P0703 </TD><TD vAlign=top align=middle>— </TD><TD vAlign=top align=middle>BOO </TD><TD vAlign=top align=left>Brake switch B circuit malfunction </TD><TD vAlign=top align=left>Open/short circuit, switch, PCM, failed to activate switch during KOER switch test </TD></TR></TBODY></TABLE>
<TABLE cellSpacing=0 cellPadding=3 border=1><TBODY><TR><TD vAlign=top align=middle>P1780 </TD><TD vAlign=top align=middle>— </TD><TD vAlign=top align=middle>TCS </TD><TD vAlign=top align=left>TCS circuit of out self-test range </TD><TD vAlign=top align=left>Circuit, switch, PCM, failed to activate switch KOER </TD></TR></TBODY></TABLE>

<TABLE cellSpacing=0 cellPadding=3 border=1><TBODY><TR><TD vAlign=top align=middle>P0571 </TD><TD vAlign=top align=middle>— </TD><TD vAlign=top align=middle>BPA </TD><TD vAlign=top align=left>Brake switch A circuit malfunction </TD><TD vAlign=top align=left>Cruise control codes will be set on every switch test on vehicles not equipped with cruise control </TD></TR></TBODY></TABLE>
<TABLE cellSpacing=0 cellPadding=3 border=1><TBODY><TR><TD vAlign=top align=middle>P0566 </TD><TD vAlign=top align=middle>— </TD><TD vAlign=top align=middle>PCED </TD><TD vAlign=top align=left>Cruise Off signal malfunction </TD><TD vAlign=top align=left>Open or short circuit, switch failure, PCM failure or failed to activate switch during KOER switch test </TD></TR><TR><TD vAlign=top align=middle>P0567 </TD><TD vAlign=top align=middle>— </TD><TD vAlign=top align=middle>PCED </TD><TD vAlign=top align=left>Cruise "Resume" signal malfunction </TD><TD vAlign=top align=left>Open or short circuit, switch failure, PCM failure or failed to activate switch during KOER switch test </TD></TR><TR><TD vAlign=top align=middle>P0568 </TD><TD vAlign=top align=middle>— </TD><TD vAlign=top align=middle>PCED </TD><TD vAlign=top align=left>Cruise "Set" signal malfunction </TD><TD vAlign=top align=left>Open or short circuit, switch failure, PCM failure or failed to activate switch during KOER switch test </TD></TR><TR><TD vAlign=top align=middle>P0569 </TD><TD vAlign=top align=middle>— </TD><TD vAlign=top align=middle>PCED </TD><TD vAlign=top align=left>Cruise "Coast" signal malfunction </TD><TD vAlign=top align=left>Open or short circuit, switch failure, PCM failure or failed to activate switch during KOER switch test </TD></TR></TBODY></TABLE>

I've cleared the codes. Gone through the steps instructed. KOER, KOER and so forth. The codes return and the check engine light comes back on.

Occasionally the check engine light wll go off for a day, or a few hours, or a few minutes.

Have gone through made sure wire harness and connectors are secure.

Is this telling me to replace the PCM?

Otherwise the truck runs fine.

 

Try replacing the fuse that powers the PCM first. It may have a hairline crack in the conductor.
Otherwise, I have to agree with your thinking, that PCM looks suspect.
OTOH, my experience with PCM's is either they work or they don't. None of this working fine for three weeks and then it's bad for a day, then back to normal.
First time for everything, but still...............

 

I would check for actual power going to the glow plugs. It does seem that the GPM has gone south.

There is a sensor on the side of the master cylinder when that goes out so does your cruise control. It is around $20 from Ford.

The TCS I'm assuming that that is the same as the TPS. These trucks drive by wire. On some models you can replace just the switch others are the whole asembly. Some have had luck by disconnecting it and spraying some electrical contact cleaner into it. Let it dry out, reconnect and see if that clears that code.

 

Another thought that came to mind is: How good are the batteries and cables?
If the batteries are marginal and/or the cables are corroded, that will do the same thing.
Voltage will drop too far while cranking for anything to work correctly. All sorts of ghost problems develope if you don't have good clean power to everything all the time.

 

Don't you love what the website is doing right now, Jim?

EDIT, well, I don't know how it happened but I saw Jim making a double post, and after I made this comment, there is only the single post.

 

I saw that Dan. I merged them together and then edited the 2nd one out. I could have deleted it but wanted to see if what I did would work. I was having less issues with Google Chrome....

 

Dan,
I don't know about Jim loving what this sight is doing, but I know I do. I posted this twenty minutes ago and I've already got more knowledge and more things to check. Gotta love it.

Thanks and I WILL let y'all know what fixes it!

 

Okay, I have a couple of thoughts on this.. so, while it appears Rickx is out looking at his truck, would we be looking for chaping wires at the PCM connection, or weak ground connection?? Being that it is intermittent??
And I will now return you to your Troubleshooting program...

 

I let my sons take the Excursion camping. They left this morning and won't be back till Tuesday. The reason I'm telling you this is you given me great response and I know you'll be looking for info on what I've done.

Here's a little more I am going to do based on what I've heard here.

I have knife switches on my batteries to be able to disconnect easily.
I put the on last year while chasing a probem with my trailer wiring. something was draining my system and blowing altenators.

I will remove them.
Then I will carefully inspect all associated wiring harnesses.

But I can't do anything till Tuesday.

 

Just throwing something out here: one fault is the brake switch B circuit. If the brake switch is sticking or not making contact, could it fail the prestart check by the PCM and also affect the cruise control? A brake switch often goes intermittent on its way to failure.

 

There have been problems with the site, making duplicate posts. Dan saw a double post that happened to me, while he was looking at it I merged the posts to get rid of the duplicate. He them thought the 2nd post just dissapeared. I did this instead of deleting the 2nd post.


Dan may be on to something with the electrical connection. Check your knife blade switch to see if it is loose corroded or anything along those lines.

 

The electrical issue is what I'll concetrate on first. I bought this 2003 Excursion new in November of 2002. The climate control didn't work and delayed delivery of the vehicle. Through the years I've been through three altenators and three sets of batteries. I bought Red top Optimas the last time and theyve lasted the longest. I had problems with the infamous door ajar switches and took me a couple of years to find apermanent fix for that. I assummed that was what was so rough on my charging system, with the lights always staying on until they timed out. I haven't had any issues since I fixed them. So I probably don't need those knife switches now.

As far as being intermittent. The check engine light stays on for days. And might go off far a short period of time.

 

Ok - I finally got around to dealing with the check engine light. Autoenginuity came up with the P0683 Code. Communcations circuit GPCM to PCM. I reseated all associated conectors. So /far - problem solved!

 

Glad to hear you got it fixed. Codes like cruise control issues, brake pedal, etc. are a result of running tests with the AE. When you do certain tests, you're supposed to push pedals and buttons in a certain order. If the PCM doesn't see you push the switch, it assumes you tried and throws a code.

Next time just have AE pull the existing code before doing any tests. The GPCM sets the check engine light because it's considered part of the emissions package. If the light happens to come back, it will be time to check the wiring from the GPCM to make sure you don't have an intermittent fault.

Thanks for the follow up on this. It's always better to hear what actually solved the problem.

 

Thanks for the info. I've still got a lot to learn with AE.