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Backstory: I bought this truck ('99 K1500 Suburban) last year in non-running condition.  Had to completely overhaul the engine.  Got it running last month and it was running pretty well.  The only thing, at the time, that it needed was the timing set (code P1345).  Otherwise it was running pretty well.

 

So last week I had a doctor's appointment.  The truck was running pretty well so I thought I would take it to the appointment.  Drove out of my neighborhood and all seemed well.  I had good oil pressure, it was still cool so no over heating.  I turned a corner on to a major thoroughfare and bam!  I just died.  Not only did the engine die, but it wouldn't even crank. 

 

I got it towed home, fortunately, it was only a few miles.  I've looked for anything obvious. 

  • Starter is new. 
  • Battery is new. 
  • Battery cables are tight. 
  • All wiring harness connectors are secure. 
  • No blown fuses. 
  • I put my code reader in the OBD2 port, but it can't connect to the truck.  This worries me. 
  • I have turned the engine over by hand so I know it's not a mechanical issue. 
  • The VATS has already been jumped with a resistor.

 

Now, the truck does have an aftermarket alarm system on it and I'm hoping it's just that.  I haven't traced that all the way out yet.  That's going to be Saturday's project.  I did jump the starter solenoid while the ignition was on.  I could crank the engine but it wouldn't run. 

 

Given all this, does it sound like it could be the ECM?  If it was a bad ECM, wouldn't it still try and crank?  Does the ECM also control the start circuit? 

 

I'm really hoping it's the alarm system given how much time I've already put into this truck.  I'm afraid that if it turns out to be the ECM, I'm just going to recover all my new parts and sell this thing for scrap.  I don't want to do that but I'm worried this truck has some bad mojo.

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Backstory: I bought this truck ('99 K1500 Suburban) last year in non-running condition.  Had to completely overhaul the engine.  Got it running last month and it was running pretty well.  The only thing, at the time, that it needed was the timing set (code P1345).  Otherwise it was running pretty well.
 
So last week I had a doctor's appointment.  The truck was running pretty well so I thought I would take it to the appointment.  Drove out of my neighborhood and all seemed well.  I had good oil pressure, it was still cool so no over heating.  I turned a corner on to a major thoroughfare and bam!  I just died.  Not only did the engine die, but it wouldn't even crank. 
 
I got it towed home, fortunately, it was only a few miles.  I've looked for anything obvious. 
  • Starter is new. 
  • Battery is new. 
  • Battery cables are tight. 
  • All wiring harness connectors are secure. 
  • No blown fuses. 
  • I put my code reader in the OBD2 port, but it can't connect to the truck.  This worries me. 
  • I have turned the engine over by hand so I know it's not a mechanical issue. 
  • The VATS has already been jumped with a resistor.
 
Now, the truck does have an aftermarket alarm system on it and I'm hoping it's just that.  I haven't traced that all the way out yet.  That's going to be Saturday's project.  I did jump the starter solenoid while the ignition was on.  I could crank the engine but it wouldn't run. 
 
Given all this, does it sound like it could be the ECM?  If it was a bad ECM, wouldn't it still try and crank?  Does the ECM also control the start circuit? 
 
I'm really hoping it's the alarm system given how much time I've already put into this truck.  I'm afraid that if it turns out to be the ECM, I'm just going to recover all my new parts and sell this thing for scrap.  I don't want to do that but I'm worried this truck has some bad mojo.

I had a conversation with my barber just last week about this problem. It’s seems that that 98-99 GMs have problems with their anti theft devices. The difference with his was sometimes it wouldn’t crank. His truck is all stock and original. He’s not very mechanical, all could tell me was his mechanic did a work around. Good luck


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They do have issues with the ECUs.  If you jumped the solenoid then it would still crank even if it was bad.  Sadly a new ECU is at least a couple hundred bucks.  Not bad but not a fun fix either.  Not connecting is another sign.  I have never had to deal with the alarm system malfunctioning but I have heard that it is an issue.  I also dont know how you would go about fixing that.  When you put your key in the ignition does the security light do anything special?

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50 minutes ago, Logan Lanfear said:

They do have issues with the ECUs.  If you jumped the solenoid then it would still crank even if it was bad.  Sadly a new ECU is at least a couple hundred bucks.  Not bad but not a fun fix either.  Not connecting is another sign.  I have never had to deal with the alarm system malfunctioning but I have heard that it is an issue.  I also dont know how you would go about fixing that.  When you put your key in the ignition does the security light do anything special?

The alarm system is aftermarket.  It was in when I bought the truck so I have no idea the brand or how it's wired.  The VATS has been jumped with a resistor.  I'm thinking I could pick up a used ECM out of the junk yard just to test, but my question is does the ECM control BOTH the start circuit and the ignition?  I don't know the answer to that, but that's what makes me suspect the alarm system.  It would seem to me that VATS would shut down one or the other, but I would be surprised to learn it shuts down both. 

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If its aftermarket I wouldnt trust it at all.  I would work on getting rid of as much that you can.  Ditch it and replace the ECU with a junkyard one or whatever you prefer.  Then try it. 

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OK, here's the $64,000 question.  If the ECM is dead, is that any reason why the truck won't start? 

After reading up on the various systems GM used over the years, it would seem mine uses "Passlock", which disables the injectors, but not the starter.  So if that's the case, maybe it is more likely to be the aftermarket alarm rather than the ECM.  I hope so because if I can't get this thing figured out in the next week, I'm going to recover my engine and new starter and sell it for scrap.

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1 hour ago, VegasJen said:

OK, here's the $64,000 question.  If the ECM is dead, is that any reason why the truck won't start? 

After reading up on the various systems GM used over the years, it would seem mine uses "Passlock", which disables the injectors, but not the starter.  So if that's the case, maybe it is more likely to be the aftermarket alarm rather than the ECM.  I hope so because if I can't get this thing figured out in the next week, I'm going to recover my engine and new starter and sell it for scrap.

If ECM is dead it won't even engage the starter.  No OBDII communication is a good sign it is maybe dead, but have you tried disconnecting the connector to the ECM cleaning it with contact cleaner and re-seating.  Also you could have lost one of the grounds.  The one that goes from the engine to the fire is one that will kill it for sure. But others will also stop it from cranking over like the ECM ground for instance which is more likely since the ECM has no power.

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Well, I found it, and I'm embarrassed.  Do you see the problem?

80-fuse1_60607429ac6f6072ff8e67c3511e366

 

What about now?

80-fuse2_0f16137160b54d451773825d1a71346

 

Sneaky little bastard.  I couldn't tell until I held it up to sunlight.  I would have thought a big fuse like that would have been more obvious.  Truck is back on the road and I don't have to scrap it (yet).  Now, I just need to figure out what caused it in the first place.

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11 minutes ago, VegasJen said:

Well, I found it, and I'm embarrassed.  Do you see the problem?

80-fuse1_60607429ac6f6072ff8e67c3511e366

 

What about now?

80-fuse2_0f16137160b54d451773825d1a71346

 

Sneaky little bastard.  I couldn't tell until I held it up to sunlight.  I would have thought a big fuse like that would have been more obvious.  Truck is back on the road and I don't have to scrap it (yet).  Now, I just need to figure out what caused it in the first place.

Don't be embarrassed, we've all probably done much worse. Glad you followed this up, I was following this and curious myself. I've read a lot of folks say the ECM usually isn't the problem, as they really really don't go bad. You're right though, there's a reason that it blew. Which fuse is it?

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That's the one for all ignition function.  And it's the main fuse too, so when it goes, all engine related electrical is dead.  Starter, ECM, fuel, etc.  Everything.  But that explains why I had all my other functions like lights and wipers.

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Back to basics. Everything starts with power and ground. Lesson learned I hope.

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OK, check this out.

Yesterday I decided to take the wagon out to see if I could repeat the failure. It's important that I explain now that the plastic covers on the steering column are off because I had to replace part of the shifter linkage.

I get gas and as I'm pulling out of the station, I turn hard right (same as the initial failure) and I see sparks coming from somewhere around the top of the ignition lock cylinder. The truck kept running and it was two quick sparks, but they got my attention.

I get to where I was going and run a couple errands. At one point, again turning right, the stereo quit working. I also noticed I lost all accessory controls, no windows, no HVAC. But the truck continued to run, although I had my ABS, Brake and Security lights on the instrument panel now.

I go out this morning to see if I can figure out what's going on and lo and behold, it's blown the same fuse. Weird that it blew the same fuse as before but completely different symptoms.

I disconnected the plug that goes to the reluctor for the Passlock system since it's already been bypassed. There does appear to be a pinched wire in there but I could not duplicate the conditions that resulted in the spark. I drove it around again, even cranking some hard right turns to try and simulate the previous conditions, but no failure.

I seriously don't trust this truck. I put a CL ad up a couple days ago for $2k. I won't lose any money but I'll lose a shitload of time if I can get that for it.

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3 hours ago, VegasJen said:

OK, check this out.

Yesterday I decided to take the wagon out to see if I could repeat the failure. It's important that I explain now that the plastic covers on the steering column are off because I had to replace part of the shifter linkage.

I get gas and as I'm pulling out of the station, I turn hard right (same as the initial failure) and I see sparks coming from somewhere around the top of the ignition lock cylinder. The truck kept running and it was two quick sparks, but they got my attention.

I get to where I was going and run a couple errands. At one point, again turning right, the stereo quit working. I also noticed I lost all accessory controls, no windows, no HVAC. But the truck continued to run, although I had my ABS, Brake and Security lights on the instrument panel now.

I go out this morning to see if I can figure out what's going on and lo and behold, it's blown the same fuse. Weird that it blew the same fuse as before but completely different symptoms.

I disconnected the plug that goes to the reluctor for the Passlock system since it's already been bypassed. There does appear to be a pinched wire in there but I could not duplicate the conditions that resulted in the spark. I drove it around again, even cranking some hard right turns to try and simulate the previous conditions, but no failure.

I seriously don't trust this truck. I put a CL ad up a couple days ago for $2k. I won't lose any money but I'll lose a shitload of time if I can get that for it.

Probably pinching a wire or shorting somewhere in the column.  I pity the poor fellow who is buying the truck with unknown issues.  I hope you declared that in the ad.  

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