GPCM codes
Laughing Gas
Joined: Oct 2008
Posts: 1,106
Likes: 154
From: Kansas City KS
I always thought the gpcm reads resistance just like we read when using a vm to test the glow plugs. I too have gotten individual codes that pointed to the bad gp. I like the fact that it takes care of this diagnostic for us.
My 01 cali van has a gpcm. And just this winter it pointed to the bad gp. It saved me some time as i replaced the 4 gp under that valve cover. Ill do the other 4 when i have better temps and more time.
My 01 cali van has a gpcm. And just this winter it pointed to the bad gp. It saved me some time as i replaced the 4 gp under that valve cover. Ill do the other 4 when i have better temps and more time.
New User
Joined: Nov 2019
Posts: 6
Likes: 0
T-wood is correct, if you have the GPCM, not just the relay, then it will pull resistance values from the individual glow plugs and can tell you which one might be bad. Forscan is great for that, even the mobile version will do it. However, my GPCM constantly throws communication fault codes and I have swapped it and for me, different GPCM has sensed different failed glow plugs. But after pulling them and testing them for resistance, if your GPC says failed glow plug, trust it because its never lied to me!
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