ive been tracking down this CHK ENG light source for quite some time now. 41! is the bain of my trucks existance. a few people have told me that the brain could be faulty my only symptoms are flickering lights and jumping gauge in dash. and the check engine light. 41 = alternator field not switching properly. what exactly does the ecm do on my truck anyway? thanks in advance
Seva

 

It controls the shift into overdrive. It manages the alternator. I think it is needed for cruise control, but am not sure.

 

Cruise, alternator, overdrive, grid heaters. That's all I can think of & alternator is only on 92 & 93.

 

More likely bad brushes in the alternator or a bad connection. The PCMs don't fail very often and when they do the symptoms are weirder.

In your situation, the absolute first thing I would check is the mian body ground on the core support by the battery.

 

2x ^ just had to replace my brushes 2months ago, same symptoms

 

already put new alt in and voltage regulator. ill try the good ground next. i have a getrag so no tranny control. i looked at the ecm and it was hanging by one screw, i took the cover off and the gel was very dry and cracked looking. thanks again

 

the ground from batt to body is solid as is to the block. is there a missing ground to core support or is what i have sufficient? would a bad ground cause a code 41? i am

 

There should be a ground wire straight from the negative batter terminal to the core support. Is it intact and clean?

 

forgive me is the core support the front of the truck basically, where the headlights and grille attatch? if so then no! as it turns out that little wire was broken off. i reattatched it and my lights seem to have evened out as well as my gauge of course i still cant figure out the chk eng light. thanks for the ground tip. ill catch on some day