electrical issues

[derekja]

Hi,

I've got a set of electrical issues I'm having a hard time resolving in a 1998 K3500. Any ideas are much appreciated. Here's what happens:

-- truck usually starts and runs great. About one time in 10, though, the glow plug light goes out right away and no matter what it won't start, it cranks, but doesn't catch. When this happens smoke also comes out of the turbo when I try. Hooking a code reader up to the truck results in a "glow plug heater circuit" code.
-- I can usually get it to start by wiggling the wires around the glow plug controller, indicating to me that something is loose in there. I've taken everything off and put it back together a couple times, though, and the problem keeps coming back.
-- several times now, the truck has mysteriously died. In each case right after going over some bumpy roads or steep hills, the same glow plug heater circuit code appears, so I presume it is the same electrical issue
-- after the last time, I also got an ABS code for "Brake switch A". The strange thing about this code is that it doesn't show up in carcode in a way that lets me clear it (usually on the enhanced page of carcode I get several servers responding and then can clear the codes they are bringing up, but the ABS server never responds.)

So, specific questions:

-- is there something internal to the glow plug controller that could be causing a problem like this? Which connection on the controller is most likely to correspond to the heater circuit? It would be the white plastic connector from the harness, not either of the bolt down connections, right?
-- where should I start looking for "brake switch A"? I presume that this is an unrelated problem since it just started happening after I went over some pretty bumpy roads, even though it appeared during one of the mysterious dying incidents.

Thanks for your help!

--Derek

[redbird2]

Sound like to me a ground issue start by cleaning the ground connection on back of head there are more electrical problems solved by this than almost anything else.

good luck

[wade-ve7trw]

The Gremlins of the electrical world are loose again. Start at the batteries and clean and check all grounding straps and wiring:bat to motor, bat to body, bat to frame, frame to body, body to motor, wiring harness to motor.

[WOODNY]

Had Same Problem It Was The Plug To The Inj Pump The Pins Were Not Making Contact All The Time And Hit Abump Would Stall Wiggle Harness And Would Start You Can Get This Little Harness From Most Anybody That Sells The Pump

[derekja]

well, cleaned and tightened all the grounds and the cables to the glow plug controller and for now the problem seems gone again. Who knows if it will stay gone, though!

BTW. an additional issue I should have mentioned last post. I have a security light on. It started this winter and doesn't seem to effect much of anything, but I'd love to get rid of it. It is B2948 antenna power short to battery or security system sensor power circuit high.

It goes away when I clear it with carcode, but comes back each time the truck is started. Any thoughts?

Thanks for all the help!

[rustyk]

Removing the bulb will partially solve the problem...

[derekja]

Aargh!

Well the problem came back this morning. Left me stranded and I had to cancel an appointment. Finally got the truck back home under it's own power, though.

It started fine this morning, but died at a stoplight about 6 blocks from home. Wouldn't restart. Wiggled the glow plug controller wires and started just fine. Drove a half block and it did it again. Wiggled ever so slightly and started again. Rinse and repeat another half dozen times on the way back home. Same glow plug heater circuit code.

Is it at all likely that there is something internal wrong with the glow plug controller? I don't feel like just pulling off and replacing the connections again is the ticket, anyway. And after having gone over the grounds and having the problem come back in just exactly the same way that feels like less of a possibility.

Any thoughts on a next step of replacing the controller?

[JohnC]

There is a crucial ground on one of the intake manifold studs near the rear of the passenger's side head. Have you checked it?

[derekja]

yes, it appears to be tight and bolts securely to the frame.

Other than just checking tightness, is there anything else to check? Smear with dielectric grease? Check continuity with a meter?

Thanks.

[JohnC]

yes, it appears to be tight and bolts securely to the frame.

That is not the one I meant. There are a number of sensor grounds as well as the main PCM ground that bolt to the engine. Any bad connection here will result in major drivability issues.

[derekja]

Well that's certainly the kind of symptom it exhibits. Today as I was checking things over again it behaved slightly differently. Instead of refusing to start, it started and then shut down a second later. (literally a second, maybe two at the outside. It definitely caught and then acted like I'd turned the key off. Did this 3 times.)

On the RH rear intake stud there are 4 wires, one big braided strap down to the frame, and three smaller wires to different parts of the wiring harness. All are securely attached as far as I can tell. (edit: well, all are definitely securely attached to the stud, what I can't tell is what happens to the wires once they go into the harness, but the plastic casing on the harness doesn't appear damaged anywhere...)

It is still reliably giving me the heater circuit DTC code. Is this sufficient evidence to conclude that my short or other wiring problem is in that area or could it be a ground well removed from there and that's just the first component effected?

Possible next steps:

1) replace the glow plug relay. (~$60, but easy to get to)
2) pull off the fuel filter and heater to look for a short beneath it. (no money involved, but I'm so not looking forward to all that disassembly to get down there...)
3) keep looking for other ground issues. (but I'm not sure where to start)

What else should I check?

Thanks again. Sorry to keep running around in circles on this...

--Derek

[JohnC]

OK, I get it. I'm pretty sure the braid belongs on a bolt on the back of the cylinder head, but I doubt if it would make any difference.

I don't have any info on the '98, but there were more than 3 wires on there in '95, specifically, PCM ground PD6; ECT, IAT and Crank position sensor; MAP sensor; Baro sensor; and Trans temp if it's an automatic.

[derekja]

Still pulling my hair out over this. I've found some issues, but not the one I need to solve, apparently. Here are the things that are off the list:

1) glow plug controller/heater circuit. I replaced the controller yesterday and cleaned all the plugs on the heater circuit. I cleared the code and it didn't come back. Yay! One problem down.

2) slow cranking, turbo smoke issue. That appeared again as soon as I got the glow plug stuff back together. A friend had a load meter and the RH battery tested bad. In fact, the side terminal connection appeared fine on the outside but was all corroded inside the battery. Kind of a dumb design, so I replaced the battery with a top connection one and the starting issue went away.

I'm left with the most mysterious issue, though. It is now manifesting itself as an intermittent shut down. Once I replaced the battery it ran for about 4 or 5 minutes and I was getting all self-congratulatory and then boom, just like I'd turned the key off. No codes set. Went to start it up and it wouldn't do so, no starter click, nothing. Went to lunch and came back, same behavior. Tightened battery connections, checked fuses, messed around a bit and it started just fine. Ran for 15 minutes with no problems. I turned it off and put away my tools. Ran it one last time and predictably, the same behavior. Shut off like I'd turned the key off, this time only 30 seconds or so after I started. Started up fine this time and then did it again.

One additional data point, when it is running the battery meter usually reads about 14 volts. Sometimes, though, it mysteriously drops down to 12.5 or so. At the same time as this happens, carcode suddenly loses the ODBII connection. The voltage comes back up, the carcode connection comes back.

I still think this sounds like a ground issue. I don't know what else to check, though. I've checked the grounds off the engine to the wiring harness, the big braids down to the frame, the battery connections, the connection from the battery to the body. Where else could I be missing?

Sigh. Thanks.

--Derek

[TAG]

Boy this one sure sounds like a bad ignition switch to me. As intermittent as it is it might be tough to diagnose. Maybe throw one in pray?

[derekja]

Ack, except they want $160 for an ignition switch! Yikes. Hard to throw that money at it without some surety that that's where the problem is. Got some calls out to the salvage yards around, though...

I was looking at that, unplugging the ignition switch and looking for bad contacts and stuff and I came across another theory.

So I have that security light on. It's code reads "B2948 antenna power short to battery or security system sensor power circuit high"

I wasn't aware that there WAS an aftermarket security system in this truck. It had never been mentioned to me and I never saw any evidence of it. But there is. There is a little black module with "hornet" on the side and getting on the net I find that this is an aftermarket security company. Thinking there's a sensor reading high and shutting the truck down rather rudely sounds like just the kind of thing a security system might do.

Sound a reasonable theory?

[edit. nope, don't think so. Talked to Hornet technical support and they deny that there is any mechanism in their security system to shut down a running vehicle. Rats, I liked that theory, too...]

[Turbo Al]

Do you have a lot of keys on your key ring?? Believe it or not we get a lot of bad switches because people put every thing but the kitchen sink on there key rings.
Al

Also check replaced the battery grounds? Eazy to check them is to put jumper cables on to battery to ground and see if it continues to run -- these things corrode inside and it is hard to find.

Al

[derekja]

Sigh. Around and around she goes, are we making progress? Noone knows.

Jumper cable to ground is a neat trick. I ran it from the negative on the passenger side battery to the engine. No change in behavior.

I don't carry a lot of keys, but I'm not the first owner on the truck, so who knows what happened before me.

More detail on current behavior:

--starts up just fine every time
--runs for 5-10 minutes
--dies like the key has been turned off (except some weird stuff on dash - high beam light showing, temp gauge creeps up to 210 - erroneously, I might add, as soon as I shut off and back on it goes back to reading barely warm)
--if I try to restart without turning the key all the way to off it never works - just cranks but never catches
--if I turn the key off for a couple seconds then back on it starts easily
--dies again within a minute or so most times after this, but sometimes runs for a good long time like nothing's wrong

The warm up makes me suspicious of the pmd. That's something I know I need to relocate someday anyway, so I might as well do that now. Would a pmd failure cause the dash weirdness? Still sounds ground-like, doesn't it?

Let y'all know what happens with a new pmd...

Thanks for all the help.

[joe bleaux]

Derekja,

I can't remember all of the procedures that you have done to fix the problem. I know you have chased ground connections but, I wonder if you have chased the 12 volt connections. Further, I wonder if you are starting off of one battery yet, the other battery's connection is intermittent.

The batteries are in parallel but the positive cable making them parallel, which goes to each battery's positive terminal, could have issues.

Joe

Sigh. Around and around she goes, are we making progress? Noone knows.

Jumper cable to ground is a neat trick. I ran it from the negative on the passenger side battery to the engine. No change in behavior.

I don't carry a lot of keys, but I'm not the first owner on the truck, so who knows what happened before me.

More detail on current behavior:

--starts up just fine every time
--runs for 5-10 minutes
--dies like the key has been turned off (except some weird stuff on dash - high beam light showing, temp gauge creeps up to 210 - erroneously, I might add, as soon as I shut off and back on it goes back to reading barely warm)
--if I try to restart without turning the key all the way to off it never works - just cranks but never catches
--if I turn the key off for a couple seconds then back on it starts easily
--dies again within a minute or so most times after this, but sometimes runs for a good long time like nothing's wrong

The warm up makes me suspicious of the pmd. That's something I know I need to relocate someday anyway, so I might as well do that now. Would a pmd failure cause the dash weirdness? Still sounds ground-like, doesn't it?

Let y'all know what happens with a new pmd...

Thanks for all the help.

[Robyn]

This sounds like a ground issue or a bad ignition switch.

Bad grounds on the engine and to and from the chasis and engine can drive these things nuts.

Be sure your grounds are good.

If the switch is bad it could cause a wierd display like this too.

Good luck

[ToddMeister]

Being that you have to turn off the ignition switch and then back on to get the truck to restart, I would venture to say the ignition switch could be the cause. You also may have an intermittent PMD issue as well. Is the PMD still mounted to the side of the injector pump (approx 3" x 4" black box)?