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Glow plug control module

3K views 5 replies 4 participants last post by  jtgf250 
#1 ·
I have been getting glow plug codes for 3 and 4 for awhile, so I replaced all the glow plugs (I used motorcraft plugs). I am getting codes for 3 and 4 again,. I pulled everything apart again and made sure that all the connections were tight (I'm also getting a lot of noise through the stereo since the replacement).

My truck is a California truck, so it has a module for the glow plugs instead of a relay. Could the codes and noise be a sign that the module is going bad?
 
#4 ·
I looked at it when I pulled the valve covers off, nothing seemed wrong with it. I will probably check that next after the module.

Yes the module can go bad, replace them pretty often.

I always measure the ohms of each glow plug by disconecting the harness above the valve cover and testing the pins (outer two on either side of the connector). Should see about an ohm of resistance, if you have one thats way off (higher) then thats your issue. This also rules out UVCH issues since the readings will be higher if the plug is backed out.

If you resistances are good then you have a bad module.
I'll give that a shot next. Thanks everyone for the help.
 
#3 ·
Yes the module can go bad, replace them pretty often.

I always measure the ohms of each glow plug by disconecting the harness above the valve cover and testing the pins (outer two on either side of the connector). Should see about an ohm of resistance, if you have one thats way off (higher) then thats your issue. This also rules out UVCH issues since the readings will be higher if the plug is backed out.

If you resistances are good then you have a bad module.
 
#5 ·
So I finally got a chance to check things out again. I tested the resistance of the pins in the connector on the valve cover, got 4 ohms for each of the glow plugs. Brand new plugs, don't think that is the problem. I think the 4 ohms is from my cheap meter and not being able to get a good connection on the pin. They were all consistent, though.

Tested the harness that plugs into the connector with the key on, got 11.9 volts at each one, so I think the GPCM is good.

I think at this point my UVCH is the problem, something is not making a good connection. Am I right in my thinking?

So my next step is ordering new UVCHs. Should I replace the valve cover gaskets along with the harnesses (they don't leak)?
 
#6 ·
They are your gasket. Shouldnt leak. Make sure your grounds are good also if getting static on your radio. 4 ohms doesnt sound good to me and .5v loss is enough for them to not work. I havent messed with a cali truck so not sure about the module and how it hooks up.
 
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