Accelerator Pedal Position Codes

[CaseyR]

When I drive over 70mph, the SES light comes on and stays on. The codes that I am getting are 65, 84, and 99. As long as I stay under 70 (actually, anytime that I hold the engine revs above some level for more than about ten seconds - unfortuntely, my truck has the wrong alternator pully so I don't know exactly when the rpm is) in fifth, I am ok. More than about ten seconds above 70 and the SES lights up.

I assume that I need to replace the APP (Accelerator Pedal Position) unit nestled under the accelerator pedal. Is that likely to be enough to silence the SES? Is there some source to get a reliable unit for less than a small fortune? I checked GM Parts Online and could not find any references to diesel APPs

I guess the other solution is to just keep well under 70 (and save fuel in the process...)

The truck is a 1994 C2500 turbo manual tranny with around 270,000 miles - most of them before I got the truck.

[kdr]

Ive got a 1994 6.5 TD with 4 spd auto since new. For years now Ive been getting a "service engine soon" light when I travel over a certain speed in third gear. As soon as I shift into fourth the light goes out. Ive lived with it because the truck still performed ok otherwise. Recently I lost throttle response altogether. The truck just idles with the "Service throttle" light on. When I shut the diesel off and restart all is ok (for now). I'm interested in what you find out.
Regards Karsten

[Warren96]

Mine is throwing code 84 also "APP Fault''.That makes three 94's in a row. I took my APP out and tried cleaning it tonight, i will let you guys know if it works in a few days.

[CaseyR]

I just installed a new J. Kennedy FSD and cooler and have been driving it for the last three days. So far it has not thrown a pedal position code even when I have expected it. It also seems to have more power than before. I will report back if the initial impression is just an illusion....

[CaseyR]

I have the new FSD and cooler from Kennedy mounted in front of the driver's side battery. Works well. I just did a run from Berkeley, CA, to Medford, OR and am no longer getting any accelerator pedal fault codes. The new FSD and cooler are the only changes I have made since I was getting the pedal fault codes any time I drove over 70. Did about thirty miles at 75 or so. I also no longer lay down a smoke screen of black smoke when I leave the cruise control engaged on moderately steep grades even though I haven't changed the air filter element lately. The FSD seems to be an all purpose cure... (Not exactly a cheap on, however.)

I still do get a 78 code if I run at 75 for a while. I think that is the turbo solenoid fault. Seems strange that I don't get it when I ran at 65 for six miles up a 6 percent grade but it does set the fault when I run 75 on the flat and level...