M1Gunner
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Check this ground G203 and the connectors at the I/P fuse block from the schematic
No crank/start/anything condition with radio also in locked mode.
- Thread starter Alberta Tahoe
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Alberta Tahoe
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There are several threads about what I had described previous to this latest condition. That is the momentary dropping out of most things electrical while driving (over bumps in particular). Most conclusions were faulty wiring. Bad grounds. Corrosion and the like. I'm well past that now with no end in sight.
I'm not certain that even the best PCM scanner (like a GM Tech 2) will be able to detect the fault seeing as the it (PCM) and the battery have been removed and reinstalled.
I'm not certain that even the best PCM scanner (like a GM Tech 2) will be able to detect the fault seeing as the it (PCM) and the battery have been removed and reinstalled.
Alberta Tahoe
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Thanks for the drawing. That's the sort of information that's really helpful.
I'll get into this truck again this week coming and post back.
Alberta Tahoe
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A follow up as promised.
I've checked the IP fuse block. Testing shows 12 volts at all fuses. That's to a grounding point I picked off the instrument panel steel frame.
There is a ground on the frame directly below the A pillar. Two bolts. Three wires. Cleaned and reassembled. Another ground on the lower rad support adjacent to the body mount. Cleaned and reassembled. On the advice of one of the senior service techs at the local Chevy dealership, I also added a jumper (via one leg of my booster cables) from the negative battery post to the engine block.
All of the above yielded no change.
From my experiences as an industrial automation electrician, it IS behaving as though part of the ground circuit is incomplete. That the ignition switch initiates the instrument panel (after the battery has been disconnected and reconnected) but does NOT turn off the instrument panel when the key is removed is very telling. What it's telling however, escapes me. It is operating as though there is a back feed of some sort keeping the IP alive.
The dealership will take the vehicle in and at $180+/hour, try and determine what the problem is. I have my doubts that they will be able to come to any conclusion judging by what I've read on problems of this sort and the results the technicians are getting.
At this point, I'm at a loss.
It would have been somewhat more comforting if I hadn't replaced the electrical portion of the ignition switch. I'm not 100% certain that I've reassembled it correctly seeing as there's no real index that ensures the "rack" in the mechanical portion of the switch operates the "gear" in the electrical portion. That said, the electrical problems I'm encountering precede having replaced the ignition switch so it may mean absolutely nothing.
Again, thanks for the input up to this point.
Still debating over what the next move might be.
At $5000 (CDN) a little over two years ago and over 60000 miles racked up since then, it certainly doesn't owe me anything. Then again, it would be nice if it was still functional. It comes in handy.
I've checked the IP fuse block. Testing shows 12 volts at all fuses. That's to a grounding point I picked off the instrument panel steel frame.
There is a ground on the frame directly below the A pillar. Two bolts. Three wires. Cleaned and reassembled. Another ground on the lower rad support adjacent to the body mount. Cleaned and reassembled. On the advice of one of the senior service techs at the local Chevy dealership, I also added a jumper (via one leg of my booster cables) from the negative battery post to the engine block.
All of the above yielded no change.
From my experiences as an industrial automation electrician, it IS behaving as though part of the ground circuit is incomplete. That the ignition switch initiates the instrument panel (after the battery has been disconnected and reconnected) but does NOT turn off the instrument panel when the key is removed is very telling. What it's telling however, escapes me. It is operating as though there is a back feed of some sort keeping the IP alive.
The dealership will take the vehicle in and at $180+/hour, try and determine what the problem is. I have my doubts that they will be able to come to any conclusion judging by what I've read on problems of this sort and the results the technicians are getting.
At this point, I'm at a loss.
It would have been somewhat more comforting if I hadn't replaced the electrical portion of the ignition switch. I'm not 100% certain that I've reassembled it correctly seeing as there's no real index that ensures the "rack" in the mechanical portion of the switch operates the "gear" in the electrical portion. That said, the electrical problems I'm encountering precede having replaced the ignition switch so it may mean absolutely nothing.
Again, thanks for the input up to this point.
Still debating over what the next move might be.
At $5000 (CDN) a little over two years ago and over 60000 miles racked up since then, it certainly doesn't owe me anything. Then again, it would be nice if it was still functional. It comes in handy.
MrBalll
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This sounds so much like electrical but it hasn't been found anywhere. Hopefully the dealership will take your word for what you've done and not waste time tracing every wire and find the issue fast.
Wonder if there is a super anti-theft mode. Or if the anti-theft sensor somehow is messed up and won't let the truck run at all.
Wonder if there is a super anti-theft mode. Or if the anti-theft sensor somehow is messed up and won't let the truck run at all.
Alberta Tahoe
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Being in the electrical business as I have, with trouble shooting as a main stay, I can't say I'd expect the dealership to take my word for anything I've done up to this point. I would always appreciate my clients input however I would be remiss if I didn't investigate their concerns on my own.This is specifically why I went to the dealership today to discuss, in person with a technician, what I've gone through and based on their advice, what I might do going forward. As it stands now, I think I'll have the heap towed to the shop and be at their mercy. I can rationalize spending a few hundred dollars for a diagnosis but my guess is that amount won't cover any significant analysis.
This forum has been very helpful with ideas and suggestions. Perhaps another will come down the pipe and save the day.
This forum has been very helpful with ideas and suggestions. Perhaps another will come down the pipe and save the day.
M1Gunner
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It's a shot from the hip but there is a couple more important grounds. One behind the power steering pump. Just double check these last two ground distribution schematics and verify they're all good.
Test if the ignition is actually doing what it's supposed to do with a test light. Move the key from point to point and see if it's moving the 12v along and if the ground stays steady. That would be my first thing. Then build some ground cables out of random cable you can get and double up on the main grounds with a fresh cable and check as you go.
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Alberta Tahoe
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Thanks for the additional drawings. I'll nose around again.
As for the ignition switch, I've managed to prove that the old is internally connected and functional like the new one so I doubt if the switch was problem in the first place. That said, I would need the ignition switch schematic and then trace the power to the various points vs the position of the switch.
I'll keep at the grounds in the meantime. It may not happen for a while (work takes me out of town for two weeks at a time).
As for the ignition switch, I've managed to prove that the old is internally connected and functional like the new one so I doubt if the switch was problem in the first place. That said, I would need the ignition switch schematic and then trace the power to the various points vs the position of the switch.
I'll keep at the grounds in the meantime. It may not happen for a while (work takes me out of town for two weeks at a time).
Alberta Tahoe
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Well, here's the latest.
First a quick summary: what started as an intermittent electrical dropout while driving over bumpy roads has turned into the title of this thread.
I have: removed and reinstalled the PCM (No replacement. Just a removal to inspect the connections and reinstalled). Used several batteries. Jumpered the negative battery post to the engine block (that on the recommendation of GM tech). Checked numerous grounds and cleaned what I found. Replaced the electrical portion of the ignition switch.
All of the above have no yielded no positive results. I believe, for whatever reason, I have put the vehicle into the anti-theft mode but have idea about how to determine this other than perhaps finding someone with HP Tuners and can crack the code in the PCM.
Now for the latest.
I jumpered the starter relay in the fuse/relay centre. The starter will engage and crank the engine with no difficulty. I also jumpered the fuel pump relay in fuse/relay centre and could hear the pump running. Doing both of these simultaneously would not start the engine.
The ignition fuses are intact and with 12 volts showing. So are the injector fuses.
There's still something missing.
What is preventing the ignition switch from doing it's job and supplying power to what I've jumpered? Is there something I can put power across and bring this thing back to life?
First a quick summary: what started as an intermittent electrical dropout while driving over bumpy roads has turned into the title of this thread.
I have: removed and reinstalled the PCM (No replacement. Just a removal to inspect the connections and reinstalled). Used several batteries. Jumpered the negative battery post to the engine block (that on the recommendation of GM tech). Checked numerous grounds and cleaned what I found. Replaced the electrical portion of the ignition switch.
All of the above have no yielded no positive results. I believe, for whatever reason, I have put the vehicle into the anti-theft mode but have idea about how to determine this other than perhaps finding someone with HP Tuners and can crack the code in the PCM.
Now for the latest.
I jumpered the starter relay in the fuse/relay centre. The starter will engage and crank the engine with no difficulty. I also jumpered the fuel pump relay in fuse/relay centre and could hear the pump running. Doing both of these simultaneously would not start the engine.
The ignition fuses are intact and with 12 volts showing. So are the injector fuses.
There's still something missing.
What is preventing the ignition switch from doing it's job and supplying power to what I've jumpered? Is there something I can put power across and bring this thing back to life?
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