Hey guys looking for help here got a glow plug delete from merchant put it in and figured while I was in there I'd clean up the harness and unpin everything from glow plug control module and glow plugs little to find out that now I have a no crank no start now and was reading after the fact about having to install a 120ohm resistor somewhere but no one seems to have ever done it. Looking for some help.
Gpcm delete help
- Thread starter LMM_Austin
- Start date
That would be a CAN termination resistor across the CAN + and - wires. You'll need a pinout for the GPCM connector to figure out which 2 wires it was. My diagrams don't go new enough to help, sorry.
The GPCM is not a termination point for the HS GMLAN - it is a passthrough. It sits in between the BCM and the TCM, so without it, there is no HS GMLAN connection between the BCM, TCM and ECM. You need to connect the HS and LS GMLAN circuits together - pin 46 to pin 44 and pin 45 to pin 43.
Different animal completely. In the LBZ, the HS GMLAN does not go to the BCM and terminates at the GPCM and ECM. in the LMM, it terminates at the BCM and ECM, passing through the GPCM. Although I'm surprised you didn't have other issues without the terminating resistors in the GPCM.
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Thanks guys I just got off the phone with Ken from stand alone harnesses and he told me that I need to just pins 40 to 37 and 36 to 33 and I should be good so well see how it goes
Might want to check the wires in those spots... Those pins are different from where Mitchell says they should be. According to Mitchell, all those spots are empty.
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I just looked at a schematic off Mitchell as well I think you're correct with pins 46 to 44 and 45 to 43. Next prime I'm having is trying to locate the pins through the dealer go figure.
It surprised me too because I always read you have to put the resistor in there to terminate the circuit.
From what I'm told you don't but we will see I'm going to hook it up tonight and I'll let you know what I find
With the LMM, you shouldn't have to - you should just have to jump the appropriate positions so that the BCM has communication to the ECM & TCM and you should be good.
So after a long debate with the dealer I finally got the pins I needed now what I've found is the pins that Ken gave me seem to be correct compared to 46-44 and 45-43 because they are not in the black connector over the valve cover. Maybe I'm missing something but I need to find a wiring diagram for the black and white connector for the engine harness.
Was Ken talking about the pins in the bale connector on the valve cover or the connector for the GPCM? The PDFs I posted with the pins 43-46 were for the connector at the GPCM.
Yes pins at the bale connector are he would like them pinned but the spots he wants already have existing wires in them so I need to know what are in those spots before I remove anything
Ok, per Mitchell, he is correct when referencing the X108 bale connector. There are two bale connectors, but I'm not sure which is which, other than to look for tan wires in 33 & 36 and tan wires with black stripes in 37 & 40. Connect 33 to 36 (Both are tan wires) and 37 to 40 (both are tan wires with black stripes). I would recommend doing your best to twist the pairs (33 & 36 and 37 & 40) together as the GMLAN wires are twisted pair. This will complete the GMLAN circuit between the BCM and the ECM/TCM. The disconnect before was I was referencing the GPCM connector and he was referencing the bale connector. I'm assuming what you are planning is remove the engine side wires from the bale connector and on the engine side connector, loop 33 to 36 and 37 to 40?
Out of curiosity, why are you deleting the glow plugs (and GPCM)? Unlike the grid heater (I assume you canned that?), they aren't a restriction and don't really have any negative that I'm aware of, but unless it's a summer/race only, they are useful. The LLY and newer glow plugs heat up so quick, even in cooler temps, that you barely notice that they're there most of the time... Although my 04 LBZ takes a very noticeable amount of time cranking before starting if I don't wait when it's <35 or so with glow plugs in mid-Missouri.... I can't imagine what it would be without glow plugs at those temps. If it were me, anywhere north of the Mason-Dixon Line or so, I'd keep them. Granted, our trucks aren't like the 1980 Pontiac Bonneville with a 5.7 that was my first car and *WOULD_NOT_START* in practically any temp without the glow plugs, but they do still help in lower temps.
Out of curiosity, why are you deleting the glow plugs (and GPCM)? Unlike the grid heater (I assume you canned that?), they aren't a restriction and don't really have any negative that I'm aware of, but unless it's a summer/race only, they are useful. The LLY and newer glow plugs heat up so quick, even in cooler temps, that you barely notice that they're there most of the time... Although my 04 LBZ takes a very noticeable amount of time cranking before starting if I don't wait when it's <35 or so with glow plugs in mid-Missouri.... I can't imagine what it would be without glow plugs at those temps. If it were me, anywhere north of the Mason-Dixon Line or so, I'd keep them. Granted, our trucks aren't like the 1980 Pontiac Bonneville with a 5.7 that was my first car and *WOULD_NOT_START* in practically any temp without the glow plugs, but they do still help in lower temps.
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Did you end up getting everything sorted with jumping the GMLAN +/- wires? Wanting to delete my glow plug wiring and gpcm as well, just for simplicity and cleaning up the wiring. *Truck does not get driven in the winter.
Based on your name, I'm assuming a LMM... All of the info should be here... In short, you need to find the GMLAN+ and GMLAN- wires going into and out of the GPCM and make sure + in is jumped to + out and - in is jumped to - out.
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