False Check Engine light on C7??

[Freightguy]

Ok so the check engine light came on the other day. No change in engine performance. The code is:
"Fuel DLV Pressr SPN 94 CM 0
Voltage Short or Above Normal Rng
FMI 3 OC 127"

So I got on the diesel forum on Reddit and was told the code was most likely for a bad pressure sensor. Then someone asked me for the serial # to the engine and said he could check to see if it was on a list of engines that may not have the pressure sensor. He came back and said it was not on the list, so it most likely did have the sensor. I was told if the sensor is present, there would be a wire going to the fuel pressure relief valve and that if I unplugged it the code should change to out of range. My engine does not have a wire going to the relief valve, so no sensor. So now this guy is telling me it is just a false light and that the dealer should just clear the code and reset the parameters so it doesnt happen again.

Anyone have the experience before? Can there be a "false light"? If there is a false light, what would trigger it?

The Reddit thread can be found here: Cat C7 Check engine light and fuel code. : Diesel

Thanks,

[akeyzoo]

I had a code trigger on my c9 indicating something similar. My engine did not come with that sensor and the ECU had to have a parameter set to indicate that. For some reason the parameter was set to sensor=yes for some reason. Perhaps a similar situation.

[Family Time]

My 2005 C7 fuel pressure sensor is on the cylinder head, threaded into a 90 degree elbow in the fuel galley next to the pressure regulator. intake manifold side rear corner (towards front of motorhome).

[Freightguy]

Originally Posted by Family Time

My 2005 C7 fuel pressure sensor is on the cylinder head, threaded into a 90 degree elbow in the fuel galley next to the pressure regulator. intake manifold side rear corner (towards front of motorhome).

You mean here?

[Family Time]

Well no, that is the pressure regulator. My pressure sensor is in the port that is about 2 inches left of the tip of your pointer. Looks like the engine in the picture has a plug in the port.

[Family Time]

I found a pic from my engine disassembly. The pressure sensor was on the 90 degree fitting with the blue cap.

[Freightguy]

That photo is very helpful. Thank you!

[akeyzoo]

Like I said, my C9 did NOT come with that sensor, but my ECU was configured for one so it threw CEL's for an out of range condition. A CAT tech had to disable that function in the ECU.

Chris

[Freightguy]

Originally Posted by akeyzoo

Like I said, my C9 did NOT come with that sensor, but my ECU was configured for one so it threw CEL's for an out of range condition. A CAT tech had to disable that function in the ECU.

Chris

I am going to try an stick my head up there again tonight. I am not sure I will be able to see the location of where the sensor might be. Your not the first person to tell me they had to get their ECU set right for not having a sensor.

I am going to CAT in the morning anyway.

[akeyzoo]

Well, this is where things get funny. CAT has a TSB for this to prevent unwarranted diagnosis. The Kenworth shop I went to doesn't read TSB's apparently and spent 5 hours diagnosing this CEL, and even ORDERED A REPLACEMENT SENSOR. Then a good CAT tech jumped in, did a facepalm, and spent the 10 minutes to update the ECU.

The service writer was almost too embarrassed to explain, and obviously didn't charge me for any unwarranted labor.

Chris

Originally Posted by Freightguy

I am going to try an stick my head up there again tonight. I am not sure I will be able to see the location of where the sensor might be. Your not the first person to tell me they had to get their ECU set right for not having a sensor.

I am going to CAT in the morning anyway.

[Freightguy]

I am afraid of that. That is why I want to see the sensor myself to verify whether or not it is really there.

[Freightguy]

Just crawled under there again and really got up pretty close. I do not have anything in the port. It is plugged just like in photo of the CAT C7 I posted. Under that there is a ground cable. So I am thinking now that I do not have one.

[akeyzoo]

Sounds great. Mine was a C9 but perhaps the same, certainly same vintage. I would lead the technician in the right direction with your knowledge to prevent unwarranted time spent!

Chris

[Freightguy]

Big 10~4 to that!