ECU gone?

[FeelthePathos95]

 

OK, guys. Back to play stump the band.

My tranny cooler lines are replaced and, knock on wood, hoping tranny escaped any major damage from recent failure that dumped out fluid. It's shifting smoothly but showing slight hesitancy when accelerating from a stop. Willing to drive it for awhile to see if that resolves or worsens.

The bad news is something weird happened to the electrical system while it sat for a week. Had it towed to shop because of dead battery and the guy there said wires from battery were fried and after he replaced them and recharged battery all gauges in dash were dead. Also no power locks/power windows, no response from blower for AC or heat, no turn signals but headlights still working. Ignition not working with key so have to start car by pulling wire and sparking engine directly. Can still turn off car with key. Oddly, stereo still works but shuts off if you turn on headlights or the wipers.

Shop guy said he fears ECU got fried.

Have seen some mentions of this happening to these rigs related to battery issues, so hoping this can be dealt with and not involve a stupid amount of time and expense.

Wondering if anyone can suggest where to start?

[Slartibartfast]

It's not the computer. The circuits that are acting up are not computer-controlled. 

 

It sounds like an issue with your fuse links, which are the small loops of wire plugged into the harness near the positive battery terminal. Fuse links are basically slow-blow fuses, and shouldn't pop on their own--hopefully if they are bad, it's due to corrosion or mechanical damage. If a link is fried or broken, or its plug is corroded, or the guy didn't reconnect the fuse links properly when he replaced stuff (sounds like he replaced the terminal?), that'll be why it's missing power to places. Could be the guy screwed up; could be something was corroded and didn't give you trouble until he flexed the harness to get the terminal off the battery. But, yeah, check that your fuse links are intact, and if the terminal was replaced, make sure the fuse links are still connected to it.

 

You may also have an in-line blade fuse holder hanging off the + terminal if your truck has/had the factory fog lights. This is unrelated.

 

The wiring diagrams in the EL section of the manual may help you narrow down which fuse link(s) aren't working right if you can't find the problem visually. 

 

Not sure about the trans hesitation. Is the fluid level correct? Might not even be the trans. Mine had an engine stumble just off idle for a while, and IIRC it was that damn MAF plug.

[FeelthePathos95]

Thanks for your reply.

My first question to mechanic about this was have you checked all the fuses and he swore that he had.

But this gives me an idea where I need to start again in trying to figure it out.

My main fear was that this would require ripping up the dash to look at wiring, etc., there.

[gamellott]

Yea, what @Slartibartfast said. I said something similar on the Axle Seal post, just saw this last 

[Slartibartfast]

The mechanic may not have thought to look for fuse links, or recognized our old-school fuse links when he saw them.

 

If you don't find something obviously/visibly wrong, turn the key on, blower to full, and wiggle wires on the + terminal until you find one that makes the blower kick on. Might show you where the problem is if it's just a weak connection.

[adamzan]

Can you share a pic of the connections at the battery? I want to see what the mechanic did. Sounds like they caused more harm than good.

[FeelthePathos95]

H

Battery and cables as they are now.

Loose yellow wire at left is out at moment for sparking battery to get car to turn over since key in ignition producing no response.

https://Imgur.com/a/KIHGYmQ

[Slartibartfast]

Looks like the smaller of the red wires coming off the + terminal goes down to that wad of electrical tape, which I'm guessing is where it connects to whatever is left of the fuse links. I see a plug behind the battery there which is probably related. I also see a white wire cut off and just sticking up next to the steering res. Get the battery out of your way so you can unwrap that tape and see what kind of mess you're working with--and if it's not as bad as the wad of tape leads me to believe, find and check the fuse links, assuming they're still down there.

 

When I replaced the + terminal on mine, I adapted the fuse link connection to the new terminal with a short copper bar. Bolts to the terminal on one end, bolts to the connector for the fuse links on the other. I assume the cable was used for the same purpose. 

 

Looking at mine again reminded me that most (?) of the links are short lengths of wire between two plugs, not loops from one plug. 

 

Worth noting, the wiring for the adjustable shocks is part of the starter harness and IIRC it goes right past the battery there, so don't go connecting wires just because they're there--make sure you know what they are first. Off the top of my head I think the adjustable shock wires are white with colored stripes, but it's been a while since I tore those out of mine. Again, the EL section is your friend.

 

I'm also curious why one ground lead goes to the bolt it's supposed to be on, while the other one is on the clamp bolt, sitting all cockeyed. I don't think that's why it's acting up, but it ain't right.

[FeelthePathos95]

Had the adjustable shocks removed not long ago since they felt pretty spent after all these years.

I moved not long and so wasn’t close to the shop I previously used. Took it to this latest guy because he was close to my new location and had solid reviews online.

Plus I thought how complicated can this be? I knew I needed tranny cooler lines replaced and that the battery seemed dead. Not anything you’d expect a mechanic to struggle with.

So it’s been weird to get this can of worms.

 

[Frenchy]

Where is the yellow wire normally supposed to go? I would suspect it has a problem on its circuit that caused your issue

[FeelthePathos95]

 

Yellow wire plugs into a panel along the side there that’s not visible in this pix. Several others connect there too.

I had pulled it out to spark the battery. Plug it back in after ignition. Such is life at the moment.

On the plus side, when I drove it on the highway the other day the engine felt good, good power, tranny shifting fine. It was just that I had no working gauges in the cabin, no ability to turn on heat or AC, no turn signals.

 

 

[adamzan]

What did that freshly cut looking white wire go to before? Also goes into the mess of tape with the red wire. Also check the meter fuse inside the cab and see if it is blown.

 

Have you spoken to the mechanic after this? These trucks aren't that complicated electrically, and don't use canbus or anything. I can't believe they just gave you the vehicle back like this... Insane.

 

Maybe the best bet is to hit a wrecking yard and grab some factory cables and get rid of this mess. Or a part out on here.

Edited March 6, 2023 by adamzan

[FeelthePathos95]

The mechanic said there were no fusible links in place when he first looked at it.

Which begs the question how the gauges were being powered without them.

All very weird and he might be lying and incompetent but I can’t prove it.

Next step is to take it back to my old shop where the guy there is already saying no promises after I told him what is going on.

I assume someone who knows what they are doing could retrofit this with new fusible links?

Tell me if that’s naive.

 

[gamellott]

That's a hot mess with creative wiring. I don't know what the additional power, grounds, and relays are for... Willy Nilly... wires!!!! 

 

There appears to be a white connector with red wires under the negative post that looks to go into a bundle wrapped in electrical tape that leads to the positive side of the battery. There should be 2 connectors. One with all red wires, one with all green (Well, that's how mine is) that also goes to the positive side of the battery. That looks to be part of it.... I'd look around there. they should be in the same wire bundle unless someone did some more creative wiring.....

 

I wonder if the mechanic connected the green wires to the ground, since green is ground in home electrical??? 

[Slartibartfast]

You won't know how bad it is (or isn't) until you get that tape off. 

[gamellott]

10 minutes ago, Slartibartfast said:

You won't know how bad it is (or isn't) until you get that tape off. 

Agreed.

 

I'm not a paid mechanic, but I have seen some pretty sketchy @!*% passed off as legit. If the wires are black and oxidized, that's the culprit!

[FeelthePathos95]

Update on that whole ordeal: So I had to do some calling around to find a guy who knew his way around these old rigs and was willing to put in the time to figure things out while my dead Path sat in one of his garage bays like a large paperweight. Good guy who put more time in it than he charged me for. Basically had to do a lot of rewiring using the factory diagrams. He said some of the fusible links were in place and some gone, and that one of the burnt wires he pulled looked like it was meant for a stereo system. So there was some definite DIY-ing at some point in the vehicle's past that worked for a long time and then one day really didn't. Bottom line is that the truck is firing right up again every time and all gauges and power windows, locks, etc., functional. I'm watching and hoping about the tranny, since when the cooler lines failed it dumped a lot of fluid quickly while on the road and I worry that the trans was damaged. So far, I've had two issues - lost 2nd gear very briefly while trying to pull into a steep driveway and I've noted that in the last two cold starts on cold mornings it has been reluctant to shift from 1st to 2nd, going up to 3,000 rpms first and once giving me a pretty hard shift. Once it's been on the road for a bit with everything warmed up it's shifted smoothly. So we'll see. The trans is not flashing any codes at me but I'm bracing myself for the possibility that it could just fail on me one day. I've had the vehicle for 9 years and have been hoping to get to 10 or more.

[Slartibartfast]

Hopefully that's got it and the trans settles down. If it keeps acting weird, check the fluid level, at operating temp, in neutral, engine running. It's a pain to get set dead nuts on, but too high or too low can make it act up.