[Armazi]

Hey guys so I’ve been around the forums and I’ve used identifix, Mitchell, alldata to try and figure out why my truck has a check engine light one for codes
P1393-GP low input bank 2
P1391-GP low input bank 1
P1395-GP monitor Fault bank 1
P1396-GP monitor fault bank 2
I’ve replaced all 8 GP’s with Motorcraft plugs replaced the valve cover harness while I was in there and the relay the last 2 codes didn’t pop up till just this morning the first 2 have been there hence why I did the glow plugs, harness and relay. It’s a California truck so I know these are special when it comes to the glow plug monitors and the check engine light. When I did the test all the glow plugs shows .02 ohms. I checked the harness for continuity before throwing parts at it all checked out also resistance in the wires checked out fine. Truck struggles to start on cold days more often then not there are times the battery gauge drops down low and the truck starts up perfectly but at times it doesn’t drop much and struggles or runs rough for the first 15-20 minutes until it warms up. I’m suspicious of the module but what do you guys think I should check or look at? It’s got 314,149 miles and it runs like a champ just doesn’t start like one unless it’s a warm-hot day.

 

[klhansen]

If it's a 1999 model year, it shouldn't have a glow plug module. The CA '99's came with a glow plug relay and a shunt on them that monitors the current going to each bank. I think Ford left those codes off the Service Manual for later years, and my '99 Service manual CD won't run on the later Windows OS, so I can't access it. I would check to be sure that the output and monitoring wiring going to the PCM is correctly installed. I think there are some older posts that describe the GPR shunt in more detail. Try a search. Checking for an operating GPR is in the Hard/No Start link in my signature.

 

[Armazi]

Okay thank I’ll double check the wires from the glow plugs to the relay and the relay to the pcm again if I find anything I’ll post it here so anyone having the same problem might have a reference

 

[Big Horn]

I know your original question is about the codes and operation of your glow plugs. But addressing your comments of hard to start on cold mornings, running great when warm, and your 314k mileage, if those are the original injectors maybe it’s time to check your clearance on your injector armatures and shim the armatures and solenoids if needed. I’ll bow to the fact that klhansen knows a lot more about these psd’s than I’m probably going to learn so I would go with his advice whether he thinks it would be warranted to check or not. If you do, there’s a ton of posts on shimming injectors on our advanced search. Good Luck.