This IH with automatic will lose power, illuminate the MIL, and have the fan clutch lock all at the same time. I'm out of my league here as I'm a retired auto/light truck guy. I'm working with a S/O ProLink but without Navistar software. DTCs that had been coming up regularly were SPN 132 FMI-4 (MAF) and SPN 2791 FMI-2 (EGR). I have seen SPN-164 FMI-1 (ICP) but that's been occasional. ICP (looking at displayed PSI, not voltage) seems appropriate when I'm testing the truck.

I wrestled with replacing the EGR assembly today (valve and actuator) and after that the EGR and MAF DTCs set as soon as I do a Key On. The fault had been intermittent but now these two DTCs are immediate. It's possible that the fault became consistent on the drive to my shop rather than being the result of my work. Not known.

I have no schematic for the engine so I'm challenged.

I'm assuming that I have a V-Ref issue affecting both sensors. Measuring voltage on the socket pins with the devices UNPLUGGED I see the following using engine block for ground:

EGR: (left to right with the latch at 6:00) 5.0V, 1.5V, 0V, .14V

MAF: (left to right with the latch at 6:00) 4.9V, 0V, 5.02V, .14V, 0V

Its been my experience that one typically sees V-Ref on both the power feed and on the sensor circuit when a sensor is unplugged. I "think" that I'm dealing with a V-Ref that feeds both sensors shorted to something at .14V

Later on today I verified my voltage readings (before composing this) and the two circuits that were at .14 are now at 4.45V. I'm betting that this circuit is a common V-ref.

I'm wondering if anyone with IH info could confirm my suspicions and send me toward any other sensors that share V-ref with MAF and EGR. I did unplug a few with no success so maybe I'm looking at a harness issue.

Happy trails,

Rusty Savignac
Owner/Technician
Savignac Solutions
Oakham, Massachusetts, USA