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Intake Ground Stud-bolt

It sounds to me like a bad PCM or one of those slight compatability issues. To try to get a handle on something like this I started snipping ground and power (battery and ignition) wires to the PCM and couldnt get this kind of fault where the SES works but something else doesnt. It was all or nothing. However, it only needed one of the two grounds to run. And my SES light also kind of flickers a little sometimes but starts every time. Now, I had experienced a case where an incompatable program would light the SES light but not glow or start the truck. in my case the only program I have found that wont work in my truck is a program for the DS4 5068 IP.

I would try another PCM for a while to see if that eliminates the issue. Your OBD2 could be more dependent on the two ground wires or a lot more sensitive to power/ground issues.
 
So far can't get the problem to repeat itself......Like when you go to the the doctor, suddenly you feel better.

But test light is handy in door pocket and when the "Ghost appears" I will check "IP fuse block" to see if something is dead and I will check "Under hood fuse block" to see if "POWER" is there also.

In the mean time I'll order a Ignition switch and change that out......But buddy said "All or nothing" with key on, but he is OBDI.

To try to get a handle on something like this I started snipping ground and power (battery and ignition) wires to the PCM and couldnt get this kind of fault where the SES works but something else doesnt. It was all or nothing. However, it only needed one of the two grounds to run. And my SES light also kind of flickers a little sometimes but starts every time.
Click to expand...

Can anyone confirm that OBDII powers up different "sections" (For lack of a better term)?..........Also STS and WTS seem to be connected in this issue......do they share the same circut or something?
 
I was able to repeat your scenario with the wrong PROM in the PCM, SES still worked but nothing else. So in that scenrio I guess I had a piece of the software working right and the rest not. It had all the power continuity and circuits it needed to put up the SES light but not the smarts to start the truck. I suppose its possible the OBDII PCM could power things up differently, like lets say your battery power isnt there but ignition power is. Or one of the two grounds is good.

Thats why I would think your PCM may be malfuncitoning. Next time it happens, tap the PCM case, or bang on the dash on passenger side and see if that gets it going. Banging on stuff is a legitimate troubleshooting method ;)
 
Buddy, when you say "SES, but nothing else"..........What about all the other "key on" dash lights,......When I'm in ghost condition, every other dash light is on/cycling, EXCEPT WTS and STS.

Dash looks normal and if you didn't know to look for a WTS and hear the "click".......you'd never have a clue, untilll you crank and she'll never fire.

Also, I "think" LP is dead as well, but I have to confirm that......If I had to bet, I'd say LP is out also. The ghost seems to take out the whole fuel system, I'll also check LP "G" connector to see if LP powers during haunting.
 
Louis,

Sounds like my WTS ghost i was chasing when i bought the truck. No fuel, no WTS(therefore no GPs), and no LP running. I'd also have loss of the STS light and sometimes a flickering SES light.

Does yours act like this? I was able to catch my issue on video.

[video=youtube;fvGgBrjWERA]http://www.youtube.com/watch?v=fvGgBrjWERA[/video]

Here's what would happen randomly at some point afterwards. Could've been 10 minutes, could've been hours.

[video=youtube;8rNLMbe5_uw]http://www.youtube.com/watch?v=8rNLMbe5_uw[/video]

Later on the issue got worse to the point where it'd stall going down the road and would just sit there and crank(no WTS, LP, or fuel). I later found out that this issue only showed up below a certain temperature, around 35*F or so. I'm guessing there was a bad spot on the PCM board that reacted to cold. Cold caused things to contract so if the board contracted enough to cause a bad contact area that would explain it. Even weirder yet, when I removed the PCM and brought it into the house to "warm" it up, the truck would fire right up every time after re-installation of the "warmed up" PCM(which just meant leaving it in the house for a while).

I never could replicate my WTS ghost on command however, no matter what i tried.

Mine turned out to be a bad PCM, possibly from welding on the backside of the truck bed with the batteries connected, but now that i see more and more issues with the WTS ghost i'm thinking i was just a lucky victim of the WTS ghost. I read somewhere that GM had a recall for their PCMs at some point. Not sure if your, or mine for that matter, would've been covered but it may be worth some digging.

With both our trucks being '96s perhaps it was an isolated issue with a bad batch of PCMs?

What plant was your rig built it? Maybe we can narrow down the WTS ghost as a bad batch of PCMs at a certain plant?
 
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The WTS ghost does seem to be 1996 specific.

Has anybody heard of any other year having that problem?

Our problem on the 96 Suburban seemed to have been cured by the new ignition switch.

iamdave0887 said:
Louis,

Sounds like my WTS ghost i was chasing when i bought the truck. No fuel, no WTS(therefore no GPs), and no LP running. I'd also have loss of the STS light and sometimes a flickering SES light.

Does yours act like this? I was able to catch my issue on video.

[video=youtube;fvGgBrjWERA]http://www.youtube.com/watch?v=fvGgBrjWERA[/video]

Here's what would happen randomly at some point afterwards. Could've been 10 minutes, could've been hours.

[video=youtube;8rNLMbe5_uw]http://www.youtube.com/watch?v=8rNLMbe5_uw[/video]

Later on the issue got worse to the point where it'd stall going down the road and would just sit there and crank(no WTS, LP, or fuel). I later found out that this issue only showed up below a certain temperature, around 35*F or so. I'm guessing there was a bad spot on the PCM board that reacted to cold. Cold caused things to contract so if the board contracted enough to cause a bad contact area that would explain it. Even weirder yet, when I removed the PCM and brought it into the house to "warm" it up, the truck would fire right up every time after re-installation of the "warmed up" PCM(which just meant leaving it in the house for a while).

I never could replicate my WTS ghost on command however, no matter what i tried.

Mine turned out to be a bad PCM, possibly from welding on the backside of the truck bed with the batteries connected, but now that i see more and more issues with the WTS ghost i'm thinking i was just a lucky victim of the WTS ghost. I read somewhere that GM had a recall for their PCMs at some point. Not sure if your, or mine for that matter, would've been covered but it may be worth some digging.

With both our trucks being '96s perhaps it was an isolated issue with a bad batch of PCMs?

What plant was your rig built it? Maybe we can narrow down the WTS ghost as a bad batch of PCMs at a certain plant?
Click to expand...
 
Did you move that wimpy little ground that goes to the screw in the fender on the passenger side?

I don't know if that ground does anything important but I moved it to one of the battery box mounting bolts & from there ran down to the frame.

The frame bolt stripped and I installed a stainless 5/16 nutcert with plenty of copper coat on everything.

The 96 is the only vehicle I have that many grounds on.
 
OK, It happened again today......While in the no start condition, ran right to the under hood fuse box, only fuse that did not have power was the "glow plugs" fuse evrything else had power and was ready to go.

Seems from the schematic the "yellow wire" that plugs into the GP controller/solenoid (we think) is not sending the signal to the circut in the PCM/computer, thus the loss in fuel system and shut down......Something to do with C6 and D7, you can see the circuts on the GP schematic.

More diagnosis to come........What say you?

My mechanic friend narrowed this down and I don't know if I'm totally sold on the GP controller having that much impact on a PCM circut.......

David you wouldn't have a Diagnostic wiring "flow chart".......Would you?..........This is what he asked me for.
 
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Youre reading that circuit backwards. Its a PCM input to give glow feedback so it can code if there is no glow when there is supposed to, and PCM and WTS light are protected by the fuse. So its not going to have power unless the PCM output to the controller is there. The Glow fuse only has power when it is actually glowing.
 
Not sure if the right glow schematic is up for a 96 yet. Its more like the 95.

the Glow fuse cannot cause the problem its only feedback for when glows are on.

This is an issue because like you were saying before parts of the PCM are not powering up. Likely from internal issue.
 

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And what about Ign switch, doesn't it power the PCM all or nothing......any feedback on that?



I wonder if Bill Heath knows anything about WTS Ghost????.....Or has seen any "bad PCM's" that caused WTS ghost?
 
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Yes, ignition switch should be an all or nothing situation. It cant just power the part of the PCM that controls the SES light. If the ECM1 fuse had power then ignition switch was working. It does have two power wires coming from same ECM1 fuse. So maybe OBDII is different and if one of those two wires into the PCM are bad it does this. You can try setting up wires to backprobe the PCM with jumpers out into the truck so you can check for voltage at both pins when the anomaly happens. Unless someone wants to test that by cutting the wires to test like I had.
 

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Louis, I can't find any diganostic chart for them, sorry. IIRC i posted the glow diagram already, but just incase.

I think the next time this happens, you need to test that a signal (appears to be 12V on the 99 digram) is going to the glow relay from the PCM. I'm sure this wiring diagram is different than yours, as my 99 doesn't have a glow plug fuse in the underhood fuse box.

GlowPlugs.gif
 
I posted the one for 96, the one from Dave is 97+ I think. They are a little different since that one does not have the Glow plug fuse, just a fusible link and glow light is only controlled by PCM. The problem could be the wrong program I suppose, since as you can see GP light on 96 gets power from glows, whereas later years it is simply grounded by the PCM.
 
That is correct. Both OBD2, PCMs have different feedback and WTS control

Technically, with the wrong program yours may still work, simple because it still gets the feedback, and would still attempt to ground the WTS light.
 
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