Hey guys need some assistance, a few weeks ago I had a shorted glow plug controller. Truck had no electrical power at all. Anyway, found it was the glowplug controller, replaced it and no problems. Now I am getting the IAH circuit fault. I trouble shot it using info from this forum and it appears it is a relay or an open between IAH and relay.

When I replaced the controller, I was not able to unplug the two small black plugs so I reused them.

Does anyone know how to unplug those small black plugs??? The harness seems to be mounted to the valve cover but I cannot see it because there are two fuel lines running over them. It will not move enough to work with it.

Does anyone have a diagram of this circuit so I can make sure I have the wires on the right terminals???

One more thing, where is a good place to get a Haynes or Chilton type manual for this vehicle?? I tried the local autozone but the book he gave me did not have any mention of Diesel motors in it.

Thanks in advance.

The glowplug controller and IAH controller are different. The IAH controller is the same for all emission types. Looks to me that you need to replace the IAH controller relay. Dealer here wanted >200 to fix and just gave me a copy of replacement instructions after I threw a fit and I replaced it myself. Can't hep you w/the glowplug thingy as CA emission models are different.

Have kin in FO Ranch. Cavender usually does my warranty work when I'm in town. You may wanna ask them if covered by Fed Emission warranty ~ John Cielack (sp) strikes me as fair ~

One more thing, where is a good place to get a Haynes or Chilton type manual for this vehicle?? I tried the local autozone but the book he gave me did not have any mention of Diesel motors in it.

Helmsinc.com

The only real manual is the Helms FSM. Comes in 5 volumes, covers all versions of our trucks, inlcuding diesel and the Allison. $ 125 IIRC.

Alldata has the same thing, as an internet subscription service.

I have both, prefer the written manual.

Ok, did some looking/testing this morning.

There is not an open between the heater and the relay, I disconnected the wire at both ends and ohmed it out. I get 10vdc for about 10 seconds at the heater when the key is turned to the on position. Truck had been sitting overnight and air temp was 60* this morning. Should be cool enough to make it turn on.

Any suggestions??

Looks to me that you need to replace the IAH controller relay.


Where is the IAH relay? I thought it was part of the same controller that I replaced, one of those heavy wires goes to the IAH.

Or, does anybody know for sure if this would be covered under the 100,000 mile warranty??