Check Engine Light Coming On When Driving Up Hills.

[JoeSquid]

I have a 1995 GMC 6.5td, no mods that I know of. When I am driving up long hills the check engine light comes on after a while, when I reach the top of the hill the light goes out. When I check th trouble codes I get a 41 and a 78. These codes are not listed in my manual. It is an f series with manual transmission. Also when I put the jumper in and turn the ignition to on the service throttle soon light and check gages lights stay on, is this normal? Any assisance would be greatly appreciated.

[JoeSquid]

I found the bottom of the exhaust crossover dented in. Could this be contributing to high EGT and thus causing the check engine light to come on while climbing hills? I have a new one on order and will pick it up tomorrow to install.

[markw8]

You'll get better diesel help from TheDieselPlace.com

 

Mark