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ECM not sending power to glow plug relay, No SES, glow plug dash lights

J

Josh Bragg

New Member
Messages
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Location
Montello, WI
hello,
I am asking for some help diagnosing my 1994 VIN F k2500 6.5 Turbo diesel. My truck recently quit running like someone turned off the key. I read and read and tested and tested and came to the conclusion my PMD was ready for a replacement. I ordered a gray stanadyne remote mount kit. Once i installed this properly I got the truck running again until i brushed against the wiring harness behind the fuel filter. It died just like someone turned off the key again. I figured i needed to clean all of the grounds that i could find. while doing this i noticed there was only 2 wires leading to the rear passenger side intake manifold ground. I have read there should be 3 total. One leads to the body (braided junk- I replaced this.) I also have a single wire coming in, which i am not sure what ground this is. It appears i am missing two ground wires that connect into one. There was a connector still on the ground location, but no wires to it. It defintely looks like it was ripped out. The odd thing is i cannot find these missing ground wires at all. The truck still started, but i could kill the motor simply by wiggling the wiring harness above the glow plug solenoid. So i dug more and more into the wiring harness until i could not get the truck started anymore. At this point there is no power from the ECM to the glow plug solenoid (yellow wire.) It will no longer start. I have power to the battery side of the glow plug solenoid. power from the pink wire. the ground wire appears to be functional as i used a test light on it. I can get the solenoid to click by powering the yellow wire at the solenoid, so i am assuming my glow plug solenoid is fine. I am hoping someone can address how i seem to be missing some ground wires. Are these the ground for the ECM? That would explain why that is not sending SES message while cranking, and why the yellow wire is not powering the glow plug solenoid.

I have read a lot about how grounds are very important. I believe i did a good job cleaning up all of the known ground locations.

How can i test the ECM? How do i check to see if it is properly grounded?

since i was able to wiggle the harness around to get the vehicle to start and stall. I was assuming i had a short in the harness. So i began tearing it apart to visually inspect the wires as best as i could. At this time the vehicle will not start. No SES. No glow plug dash light. no clicking. no power from the yellow wire at the glow plug solenoid.

Hoping what i am writing is making sense. Thank you for your input. I am new to posting myself so hopefully i gave enough information.
 
You are on the right track that the problem is in the harness. It is rare I recommend completely removing the plastic off the harness, but that is what I would do here.
Other than that -the powerprobe open and short circuit kit can help chase the problem.
 
I will look into purchasing a powerprobe as mentioned. I have the wiring harness torn open now, and i have not seen any defects.
Hoping to find out too what the missing ground wires are for. I am specifically missing two ground wires that other individuals have mentioned. I have a connector with wires ripped out that was on the passenger side rear intake manifold ground. I see no sign of this wire, only the wire connector.

Thank you for the feedback.
 
I think the bulk of my issues are the ECM. I am not convinced it does not work, but there must be a wiring short. This was one of the few times i havent been able to find the right forum to diagnose my issue.
Terrible spot too leaning over the engine is no fun.

Thank you for your help gentlemen.
 
If your missing those grounds you'll definitely have issues.
Did this start all at once or happen slowly building up to the no start no glows? I've never seen wires just disappear.
 
ak diesel driver said:
If your missing those grounds you'll definitely have issues.
Did this start all at once or happen slowly building up to the no start no glows? I've never seen wires just disappear.
Click to expand...

This definitely started all at once. While the truck was idling it just shut off like someone turned the key off. Based on my research and testing of the PMD wires i believed it to be the issue. So i ordered a gray stanadyne remote mount PMD kit, with the cooler, and #9 resistor. It started up no problem once this was completely installed (properly grounded.) I also decided cleaning the grounds would be beneficial. the real issue came up while i was wiggling the fusible links coming off of the glow plug relay. I had the truck running while doing this and the truck died just like someone turned the key off. I was able to replicate this multiple times, and as i started opening the wiring harness the ability to start again vanished. I am know at a point where the truck will not start. No SES lights, no glow plug lights, no power from the ECM to glow plug relay (yellow wire.) I do have power at the pink wire as well as the battery side wire connection.

Whatever i did seems to have either caused a short or open in the system.

does anyone know what yellow wire on the ECM controls the glow plug relay.

I am assuming the problem could be anywhere, i have exposed all of the wiring harness i can get to with no obvious issue.

I read there are two power wires to the ecm, can anyone help me identify these on the ECM?
I would like to start with seeing if the ECM is getting power (both.)

Thank you all for your time.
 
Hello Josh, welcome to the forum.
I would start by replacing that problematic fusible link.
If You lay a 4X4 block of wood on top of each battery, then lay a 2X6 or 8 or 10 across the blocks, You can lay down atop of that and get a whole lot more comfortable working on the back of the enjun.
 
Can anyone identify the four wires that go down behind the motor? The four wires consist of black( the cause of my issue) a tan or brown and white, a purple, and a red/black wire. I cannot see where these go.

Two wires are broken the black and the tan/ white. The broken black wire was the cause of my no start issue. I simply grounded this to the engine block, and everything works again.

I am not sure where the tan/white wire is supposed to go, since it is behind the motor i cant seem to get a visual. Top side or from underneath. The wire has power when the key is in the on position but not while the truck is running. It does not cause any issues being unconnected, however that doesn't mean it wont haunt me later down the road.
Does anyone have any idea what this wire is for?

These four wires were all in the same plastic wire protector headed down the back of the engine on the left side of the fuel filter. Any help here identifying the tan/white wire will greatly appreciated.

Thank you all for your help. Ground issue strikes again.
 
Blacks is usually ground.
Now I might be wrong on this but, I think I was reading a post where someone was having problems similar to Your aaaand, I do believe there was a tan wire hooked in the same terminal with a black wire.
I thought it should not be there since they said it had power to it, but, I was corrected and that tanish wire is suppose to be grounded. It was hooked together with a black wire, in the same terminal from the factory.
 
MrMarty51 said:
Blacks is usually ground.
Now I might be wrong on this but, I think I was reading a post where someone was having problems similar to Your aaaand, I do believe there was a tan wire hooked in the same terminal with a black wire.
I thought it should not be there since they said it had power to it, but, I was corrected and that tanish wire is suppose to be grounded. It was hooked together with a black wire, in the same terminal from the factory.
Click to expand...

That is certainly interesting to say the least. is there something that would show me the color of the two wires at this particular ground location? It would explain how i was missing two wires. in post #7 i attached a photo of the two wires being grounded to the same location, unfortunately it does not tell me much other than there should be two wires connected there. I am referring to G105 location if you take a look.

The curious thing for me is there is power while the key is on, but not while the truck is running. Right now i have that wire unconnected to anything.

Does it seem wise to just ground it and see what happens? Thank you for the advise.
 
Do not ground a wire unless you know what it is!

I think, because I don't remember, that the wire you broke gets tapped for power with 4x4 thermal actuator motor upgrade kits and is actually supposed to be hot. But that could just be a tan wire without a stripe. Check your fuses in case one popped from the wire breakage and then test the 4x4. I would look at the 4x4 schematics and see if the wire color is listed there.

I assume you are referring to the always in the way during an engine swap harness jump from the firewall over the top of the transmission?
 
Here's your ECM Grounds. Tan/White wire and a Black/White wire at the G-105 position (per the 1997 Diagram attached). G-104 is at the top of the picture w/ the ground strap visible. Yes, they should be at G-104 but...nevermind. Regardless, White/Tan and Black/White wires are what you're looking for. The other tan things are pine needles...you're not looking for those.
ECM Grounds.jpg

Also, here's the ground schematic and diagram. As you can see in the schematic, that Black/White wire hits a lot of components.
 

Attachments

  • ECM Ground Diagram.pdf
    886.9 KB · Views: 42
  • ECM Ground Schematic.pdf
    606.7 KB · Views: 36
WarWagon said:
Do not ground a wire unless you know what it is!

I think, because I don't remember, that the wire you broke gets tapped for power with 4x4 thermal actuator motor upgrade kits and is actually supposed to be hot. But that could just be a tan wire without a stripe. Check your fuses in case one popped from the wire breakage and then test the 4x4. I would look at the 4x4 schematics and see if the wire color is listed there.

I assume you are referring to the always in the way during an engine swap harness jump from the firewall over the top of the transmission?
Click to expand...

I tapped a brown wire below the large plug behind the FFM for the 4wd actuator. I traced it back to the transfer case.

How did this wire become broken or dislodged?
 
MrMarty51 said:
Hello Josh, welcome to the forum.
I would start by replacing that problematic fusible link.
If You lay a 4X4 block of wood on top of each battery, then lay a 2X6 or 8 or 10 across the blocks, You can lay down atop of that and get a whole lot more comfortable working on the back of the enjun.
Click to expand...

Or just buy an over the top creeper - Sure wish I had one.

Once upon a time I managed to get my pants caught on the hood latch. I could not get myself lose.
Lucky for me - maybe - a friend stopped by to drink beer at me while I did whatever I was doing. He got me lose, but it wasn't painless - no physical pain - just a little pain in the pride

I run a few auxiliary grounds on my vehicles. I run a 10 ga ground to the stud shown - as I have seen that stud lose continuity on more than one vehicle.

I add a ground to the battery box on the right/passenger side. I have to take the battery out for that. This is to augment/replace the cheesy ground screw in the fender that I have had issues with over the years.

I add a ground to the frame - by the starter - where the braided ground strap attaches. I use anti-seize on all connections.

I do the battery bolt mod and run these extra grounds straight from the battery.

I also add a ground from the heater blower to the dash mount bolt just inches away.

I have taken to replacing the engine harnesses on all of my 6.5's as I work on them. My harnesses have had broken clips and looked kind of ruff in general. If it saves me searching for one bad connection - one time - it's worth the money and time spent to install a new engine harness to me.

I never got my engine harnesses from Quadstar but they seem to sell top quality products.

https://quadstartuning.com/products/6-5l-engine-wiring-harness
 
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