Updated C7 injector harness PSA

[GeneralDisorder]

I replaced the ECM to engine wiring harness on my 2008 M1079 A1R due to multiple occurrences of connection issues with all three of the pressure sensors - the oil pressure, boost pressure, and atmospheric pressure sensors would throw codes and the boost pressure sensor in particular would put the engine in limp mode and cut off all boost from the turbo making the truck REALLY difficult to drive.

In the process I found that the new harness didn't match the existing injector harness. Apparently CAT changed the design and you'll see why in a moment.

My truck has always had an intermittent slight roughness to the idle - it only seemed to do this after idling for a while and I figured it might be related to the emissions programming since the C7 trucks have catalytic converters and there are directives about putting them on high idle if they are going to sit and run for an extended time. It wasn't serious enough to consider an actual problem and never affected performance, etc. I now think this was likely due to the injector harness being damaged and shorted. Has not occurred since though I only just completed the repairs yesterday.

So the injector harness had to be changed to match the new engine to ECM harness, and in the process I found that the wiring harness had shifted and pulled loose from one of it's anchor points due to hardening and shrinking of the wire insulation and braided plastic sheathing. This caused the harness to rub against one of the valve springs to the point that it was down to the bare wire and was clearly shorting at least intermittently to the valve spring. In addition the Amphenol connector used for the rocker cover riser had failed and was allowing oil and condensation into the plug's electrical connection.





Here is the harness retainer that pulled loose from the riser (could not put it back - the harness is "baked" into a very rigid condition):







CAT has an updated harness that changes the bulkhead fitting and the main connector to the injector sub-harness and a "clip" that guards the wire in this exact location:







New style harness connector:



These are the part numbers for the harnesses and the "clip" (guard), and the new style retainers that are christmas tree style zip tie lugs:

(1) ECM and engine to injector sub-harness: 6150-01-524-8191, 229-9765
(1) Injector sub-harness: 6150-01-524-8364, 520-1511
(1) Injector harness "clip" (cable guard): 519-5559
(eight) Cable strap: 206-1345

The updated ECM and engine to injector harness (229-9765) also eliminated the lift pump fuel pressure sensor connector. Apparently it's not used anymore and indeed my ECM didn't care and doesn't even seem to have a data stream for that sensor and is still able to calculate fuel consumption - so one less thing to worry about going forward.

 

[fuzzytoaster]

What is the cost for this repair/MWO?

 

[GeneralDisorder]

Took me most of a day.... I would guess ~6 hours. That's replacing the entire harness back to the ECM though and removing the riser completely for cleaning and installing the injector harness and replacing the riser and rocker cover gaskets (both the same gasket).

Parts aren't cheap. Injector harness is around $300 with the clips, etc. ECM/Engine harness is around $900. Gaskets were like $30 each. The oil pressure and boost pressure sensors were around $275 each. I am not screwing around with non-genuine parts and being stuck somewhere so I got everything from my CAT dealer for my engine serial number. Everything was in stock except the ECM/Engine harness - that was special order.

 

[Mullaney]

Took me most of a day.... I would guess ~6 hours. That's replacing the entire harness back to the ECM though and removing the riser completely for cleaning and installing the injector harness and replacing the riser and rocker cover gaskets (both the same gasket).

Parts aren't cheap. Injector harness is around $300 with the clips, etc. ECM/Engine harness is around $900. Gaskets were like $30 each. The oil pressure and boost pressure sensors were around $275 each. I am not screwing around with non-genuine parts and being stuck somewhere so I got everything from my CAT dealer for my engine serial number. Everything was in stock except the ECM/Engine harness - that was special order.

.
Ouch!

But like you said - having Genuine CAT does have value.

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[GeneralDisorder]

Ouch!

But like you said - having Genuine CAT does have value.

Yeah and if you buy some Amazon or eBay thing who knows if it's pinned correctly and especially for the injector harness the proximity to moving engine parts, being bathed in hot oil - too much potential for it being made incorrectly or of the wrong materials and end up getting sucked into the valve train or disintegrating into the oil pickup - yeah not screwing around with any of that. Decades in the trades and in the military has learned me a thing or two on the value of original equipment parts.

 

[DannyBtruckn]

Why did they make the harness so short? Maybe some MBA six sigma clipboard warrior figured they could save a few cents per vehicle?

 

[GeneralDisorder]

Why did they make the harness so short? Maybe some MBA six sigma clipboard warrior figured they could save a few cents per vehicle?

I think it's more a case of the harness has to be just the right length to not touch any of the moving parts under the rocker cover but they didn't account for the plastic insulation and sheathing shrinkage due to engine heat and it shortened some areas and bulged the wire toward the valve spring in this one critical area allowing the spring to wear through the insulation due to the vibration and friction.

 

[DannyBtruckn]

I think it's more a case of the harness has to be just the right length to not touch any of the moving parts under the rocker cover but they didn't account for the plastic insulation and sheathing shrinkage due to engine heat and it shortened some areas and bulged the wire toward the valve spring in this one critical area allowing the spring to wear through the insulation due to the vibration and friction.

Is this the same harness that plugs into the oil pressure sending unit?. Im still reading no oil pressure on my C7. (Haven’t completed troubleshooting yet) but I did notice the wire branching out to the 3pin Deutsch connected was very short.

 

[GeneralDisorder]

Is this the same harness that plugs into the oil pressure sending unit?. Im still reading no oil pressure on my C7. (Haven’t completed troubleshooting yet) but I did notice the wire branching out to the 3pin Deutsch connected was very short.

I had the same problem with my oil pressure till I changed out the harness connector and the sending unit. Then recently I started having the same problem with the Boost pressure sensor (goes into limp mode with zero boost) and the atmospheric pressure sensor. At that point I was suspect of the entire harness so elected to change out the whole thing. The harness for the pressure sensors is the one that goes to the ECM - the injector harness is separate but if you do one you have to do both since CAT changed the connector and bulkhead fitting for the injector harness so a new version of the engine/ECM harness will not plug into the old injector harness - that's how I found this issue by pure luck. I was going after all the other sensor connectors due to the pressure sensor faults.

 

[aw113sgte]

Regarding the oil in the amphenol connector. I don't have proof but I've heard many times that oil can get into the wires and capillary from one spot to the other. So it may not be the Amphenol that's bad but it could have been one of the plugs bathed in oil that allowed a leak path.

 

[GeneralDisorder]

Regarding the oil in the amphenol connector. I don't have proof but I've heard many times that oil can get into the wires and capillary from one spot to the other. So it may not be the Amphenol that's bad but it could have been one of the plugs bathed in oil that allowed a leak path.

I've seen that but it's usually with the type of harness insulation the Germans tend to use. Mercedes has had problems with that on their transmission harnesses wicking ATF into the computer. In this case it appears the AMP connector has the wires potted into it on the inside of the valve cover and the potting didn't bond to the wire insulation. Probably was a poor choice to begin with but things like this happen in Mil-Spec land. $300 (maybe more - that sucker is no joke) Amphenol 12-pin bulkhead connector and used wire with the wrong insulation or the wrong potting compound, etc. My truck has 13k miles on it but did fend for itself in Kuwait and El-Paso for 15 years only being driven 2k miles by the military in that time.