I need help guys. Check Engine light came on on Saturday. Took the truck to Auto Zone to read the codes. Dude told me one or more glow plugs was bad. Didn't ask for the codes (dummy) and went on. Been driving the truck with no problems until this evening. Got in the truck to drive home. Volt meter was above 12 volts but never got above 14 volts. No other telltales came on or DIC. Drove home and checked battery voltage, was 12.15 volts. Shut off the truck, checked again, stayed at 11.78 volts. Isolated passenger side batter by disconnecting it, passenger was 12 volts, driver was 11.5 volts. While checking the batteries I smelled something electrical. Looked around the GPCM and noticed some smoke, electrical smell. I had a meeting I had to get to so I took the truck to the meeting, noticing the voltage getting lower. Went to the meeting, came out a hour and a half later, and the truck was completely dead, nothing. Got a ride home and came back to the truck later, checked the battery voltage again and it was 0.5 volts. My guess is something shorted in the GPCM draining the batteries with out the key switch on. Can I disconnect the large main power wire that is going to the GPCM and still jump start my truck? Just don't know if disconnecting it will cause other issues. This is my daily driver so I need to get it up and running again quickly. Any help would be greatly appreciated.
Help: Dead Truck - Glow Plug Module Maybe
- Thread starter PhilsLB7
- Start date
you can disconnect the big power wire to the glow plug controller and drive it.
Provided it isn't stupid cold where you're at it'll start fine. But will throw an engine light. I ran my 02 like that for a few months when it had glow plug relay issues. Hopefully it didn't damage any glow plugs by sticking on. If your batteries are that dead though you may want to give them a slow charge with a battery charger instead of shocking them by jumping it then having the alternator give them everything it's got
Sent from my SAMSUNG-SGH-I337 using Tapatalk
Provided it isn't stupid cold where you're at it'll start fine. But will throw an engine light. I ran my 02 like that for a few months when it had glow plug relay issues. Hopefully it didn't damage any glow plugs by sticking on. If your batteries are that dead though you may want to give them a slow charge with a battery charger instead of shocking them by jumping it then having the alternator give them everything it's got
Sent from my SAMSUNG-SGH-I337 using Tapatalk
Is it better to disconnect it at the glow plug controller and tape it up or disconnect it in the fuse box where the main battery wire connects to the 175amp fuse (before the fuse, not after)?
Right now it's not that cold and I have someone that will look at the GPCM and glow plugs with me but I need to get it to his shop on Saturday. Unfortunately I am running Optima yellow top batteries so I was told I can't use a traditional battery charger to charge them. But I do agree with you that shocking them by jump starting may not be a good idea.
Right now it's not that cold and I have someone that will look at the GPCM and glow plugs with me but I need to get it to his shop on Saturday. Unfortunately I am running Optima yellow top batteries so I was told I can't use a traditional battery charger to charge them. But I do agree with you that shocking them by jump starting may not be a good idea.
Either place. Disconnecting and taping at the glow plug relay is easier. I can't say about charging the optimas though
Sent from my SAMSUNG-SGH-I337 using Tapatalk
Sent from my SAMSUNG-SGH-I337 using Tapatalk
Update - Batteries wouldn't hold a charge so I had to get two new ones. Luckly one was covered under warranty. Got them put in today and took the truck to someone that could properly read the Check Engine codes. He told me it was the intake heater, not the glow plugs as I was originally told, and the GPCM that were bad so it looks like I'll be ordering some parts later today.
You should have the style that has a relay for the glow plugs and a relay for the intake heater. Pull the GPCM off, open it up and replace the relay inside. However Id test the relays first. Sounds like you were not even getting correct charge from the Alt to begin with though...
Yes I do but there was smoke coming from the GPCM when this problem started so I'm pretty sure it's fried. Otherwise I would agree with you to just replace the relay(s).
Alt seems to be charging fine. The GPCM turned the intake heater and glow plugs on and never turned off (something shorted somewhere). The Alt can't keep up with that current draw until the GPCM kicks off but I will keep an eye on it.
What I'm saying is...when you open the gpcm up you will only find 2 relays...nothing more. Go to parts store or online and pick up the $11 relays and replace them.
Gotcha. My only concern is if the relay(s) got hot enough and melted/damaged the relay connector in the GPCM, new relays would do me no good. But it may be worth a look. Do you know which relay(s) I need to look for at the local parts store?
Last edited:
Alright guys I need help on this one. I replaced the IAH and GPCM today. Thought it would fire up, check eng light would go off, and all would be good. However, no luck. GPCM kicked on and stayed on so I disconnected the batteries real quick. I called Scott (blk smoke lb7) and he gave me some trouble shooting suggestions.
- I removed the wire from the IAH to see if the GPCM would turn off. It did so I know the trouble is with the IAH side of the GPCM.
- Next, with the wire still removed from the IAH, I started the truck and checked the voltage at the GPCM for the glow plugs and IAH. Glow plugs were 12 volts until it kicked off, then 0 volts. However, the IAH was like 4.75 volts and when the GPCM kicked off it went up to 5.75 volts. I don't understand this.
- Then I checked the IAH at the GPCM with the truck completely off and the IAH had 0.12 volts on it. Glow plugs were at 0 volts.
- I checked all the wiring in and around the fuse box. Pulled the finder liner and checked the wiring around the ECM. All looked good but I honestly can't say that for sure.
- I checked all the fuses in the fuse box and all are good.
Why wouldn't there be 12 volts on the IAH circuit coming from the GPCM? Anyway I need more suggestions guys.
- I removed the wire from the IAH to see if the GPCM would turn off. It did so I know the trouble is with the IAH side of the GPCM.
- Next, with the wire still removed from the IAH, I started the truck and checked the voltage at the GPCM for the glow plugs and IAH. Glow plugs were 12 volts until it kicked off, then 0 volts. However, the IAH was like 4.75 volts and when the GPCM kicked off it went up to 5.75 volts. I don't understand this.
- Then I checked the IAH at the GPCM with the truck completely off and the IAH had 0.12 volts on it. Glow plugs were at 0 volts.
- I checked all the wiring in and around the fuse box. Pulled the finder liner and checked the wiring around the ECM. All looked good but I honestly can't say that for sure.
- I checked all the fuses in the fuse box and all are good.
Why wouldn't there be 12 volts on the IAH circuit coming from the GPCM? Anyway I need more suggestions guys.
