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Discussion Starter #1 (Edited)
2002 F250 PS


OK, was able to debug it a little bit more.

1) I do have 12V power to the main lug. Fuse links are ok.
2) I have 12V ignition switch power to the control lug.
3) The "cold" side of the control lug never gets pulled down to energize the relay. Both lugs for the relay winding are always at 12V.
4) I checked #22 fuse, along with almost every other ignition fuse I could find.
5) Air intake heater relay works as it should.


I clearly need to ring out the wire to make sure I don't have a break between the gpr and controller. Any suggestions?

Also... is there an engine sensor that controls whether or not the Glow plugs turn on or not? Perhaps engine oil temperature? Seems odd that the air heater works and the GPR does not.

Thanks....
 

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replace solenoid if not getting 12v one the other side
 

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Discussion Starter #3
replace solenoid if not getting 12v one the other side
Thanks...


No, it is not the relay. I have 12V on both the keyswitch side of the small control lug and the PCM side of the control lug. It appears that the PCM is not turning on to energize the coil on the relay. I either have a broken wire or a bad connector, or the PCM is shot :-(
 

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The PCM grounds one of the small posts to energize the relay. Have you tried putting 12v to one of the small posts and then the other to ground?
 

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Discussion Starter #5
The PCM grounds one of the small posts to energize the relay. Have you tried putting 12v to one of the small posts and then the other to ground?
No... no need yet. If I have 12V on both posts, that means that I'm not connecting the cold side of the relay to gnd through the PCM. If I can get the PCM to pull its connection low, AND the relay still is not coming on while 12V on the other side, then it is time to debug that relay. Right now the control signals to the GPR are not working.
 

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Discussion Starter #6
Well, tried unplugging the oil temp sensor, hoping the PCM would energize and pull the relay in. No joy. The PCM wire on the GPR is still at 12V dang.

Looks like i have to ring out the wire and check for continuity at the PCM.
 

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Have you checked to be sure the activation wires are on the right relay? I say that because you said that the IAHR activates, but the GPR doesn't. Normally, the IAHR will only activate on extended idle, if the intake air temp is below 32F, after the GPR had timed out (VPWR between 11.8 and 15V), and if you have come off idle, it won't activate at all.
The GPR activation is controlled using Engine Oil Temp. If EOT is above 131F, the GPR won't activate at all.
The GPR to PCM wire should be violet with an orange tracer, and the IAHR to PCM wire should be solid violet. It's worth checking before you go to the trouble of checking continuity back to the PCM.
 
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