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ignition switch circuit craziness

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ignition switch circuit craziness

  #1  
Old 07-04-2018, 10:03 AM
jwwcincy
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Unhappy ignition switch circuit craziness

Hi All. Just found the forum, looks like a wealth of knowledge here. I searched the threads though and can't find my problem so I'll just lay it out, hopefully someone else has had this and figured it out.

Got home two days ago and turned the ignition switch off and removed the key and the truck ('98 1500) continued to run. Had to stall it to get it to stop. Then after it was stopped all the dash lights were still on as if the key was in and turned to the second click. Had to disconnect the battery because I was sure it would be dead the next day if I didn't.

Reconnecting the battery caused a lot of clicking from the fuse/relay box, and some of the dash lights were blinking on and off.

Quick search of the internet suggested it was the circuit for the ignition switch. I thought that made sense, maybe the circuit was worn and I had an intermittent short making it think the key was on. Got a new one and swapped it out but had the exact same symptoms when reconnecting the battery.

Proceeded to swap relays for non essential items then eventually pulled all the relays and it is still happening. Something in the path is causing the power to flicker on and off (relays clicking, dash lights coming on and off) but I don't know what else it could be.

One final symptom...while the battery is connected and all this flickering is going on, if I try to start the truck, it just barely begins to give juice to the starter then stops and everything goes completely dark and dead until I disconnect the battery and reconnect it again (and the clicking starts again).

So, as I said, I'm out of ideas. Has anyone here ever experienced this and fixed it. Or if not, does anyone have an idea about what could be causing this. I'm pulling the little hair I have left out!

Thanks
John in Cincy
 
  #2  
Old 07-04-2018, 10:27 AM
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Welcome to DF.

You have two problems.

One: Short to power. If changing the ignition switch didn't solve the initial issue, need to start checking wires, and see where the short is.

Two: Bad connection at the battery.
 
  #3  
Old 07-05-2018, 02:40 PM
jwwcincy
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Originally Posted by HeyYou View Post
Welcome to DF.

You have two problems.

One: Short to power. If changing the ignition switch didn't solve the initial issue, need to start checking wires, and see where the short is.

Two: Bad connection at the battery.
Thank you HeyYou for the suggestions. Good and Bad news.

Good news is that I've confirmed it is not battery connections. Parts store confirmed the battery was in bad shape and when I installed the replacement I can start it now after it does all its clicks, but I can't shut it off without stalling it. So...

Bad news is that it is likely a short somewhere in the ignition circuitry, which was my original theory when this happened. Only thing is, after changing the ignition switch circuit out and swapping relays, I'm not sure what else in the circuit it could be. I don't have a wiring diagram.

Is there anything between the ignition switch circuit in the steering column and the fuse/relay box that could be shorting?

Is it possible that the wires themselves have the insulation worn off somewhere in between and are shorting?

Any other thoughts?

Thanks all
John
 
  #4  
Old 07-05-2018, 04:59 PM
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Trouble is, LOTS of stuff needs to be powered for the engine to run. PCM, fuel pump, ignition system, etc. So, your problem is likely between the ignition switch, and the fuse block in the side of the dash. May end up having to unwrap that harness, and see if anything obvious presents itself.
 
  #5  
Old 07-06-2018, 06:51 PM
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Did you look at the wire harness(engine bay) for any rodents making a meal out of the wires? This is the first thing that comes to mind. If you find none you may want to disconnect the crescent shaped plug at the lower column. It's either under the plastic thing covering the lower part of the column or it's under the lower plastic part of the dash. The wires from it go to the ignition switch. By disconnecting it it will rule out any issue with the switch. I believe the pcm gets at least two hot wires from the switch when running. If that doesn't stop it from running you definitely have something going on with the wiring from that plug to the pcm/distribution center(engine fuse box). Oh, And does this truck have any aftermarket alarm or remote starter installed in it? If so it could be the relay module for it could be sticking.
 
  #6  
Old 07-06-2018, 08:19 PM
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OK, so more info now:
1. All the clicking (relays being energized on and off and dash light flicking) happens even if the ignition switch circuit is removed - so any problem is happening upstream of the ignition switch
2. Found the manuals (thank you jasonw) and determined that the only way the engine can continue to run after the key is removed is if the ignition coils and fuel injectors are being powered by the ASD relay.
3. From what I can tell, the ASD relay can only pass voltage with the key off if it is internally shorted or getting a signal on its input that it should be activated
4. Again, from what I can tell, that signal comes from the PCM, I'm guessing that the PCM is messed up and with the key off it is still sending to the ASD relay, so the engine keeps running

This seems to make sense since when I connect the battery I get all the clicking and light flashing, then the engine continues to run after the key is turned off. I think the PCM is having epileptic fits or something.

Does anyone have any experience with swapping out the PCM? Does this have to be programmed by a dealer????

Thanks for the help
 
  #7  
Old 07-06-2018, 08:24 PM
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Hi Moparite - thanks for your thoughts:
1. inspected the wiring and can't see any rodents at work
2. I'll go look for the crescent shaped connector on the column and try what you suggest even though I think I got the same result by pulling the ignition switch circuit out.
3. Nothing aftermarket at all

Keep the ideas coming if you have them
 
  #8  
Old 07-06-2018, 08:56 PM
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PCM just does what it is told to. In order to run the engine, it has to think it is supposed to. Turning off the key *should* switch of power to various parts of the PCM, and the engine should quit. Take a look at the connector pinouts for the PCM, see which pins are supplying 12 volts, likely, one of those circuits is the problem.
 

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