Hey guys
A buddy of mine has a 98 12v auto that started acting up badly tonight.
His gauges all started acting up speedo quit, tranny shifting eratic, tach dead the whole works.
He managed to limp home but???? This morning when he got to work his brake lights stayed on so in the dark he fished around under the dash looking for the brake light switch is there a single wire under there that would cause all these problems? He said he didnt yank on any wires? Any body got ideas? Thanks

 

There's a BCM (body control module) that may have something to do with it, but I haven't a clue how to troublehsoot it. I only know about the BCM because it's what controls the cargo light and was bad on my truck when I bough it. It controls al kinds of things in the cab, brake lights and gauges being good candidates for this.

Chris

 

Does the 98 have the speed sensor in the rearend? if so the symptoms fit the sensor dieing.

 

Yeah I was wondering about the PCM also but I realy have know idea what each one of those moduals controls or what symptoms they would show when acting up. Im thinking he banged somthing loose under there but what could wipe out all those functions ?

 

See if the A/C is dead, if so it might be the crankshaft position sensor, it tells the pcm the motor is running, if its out all of the above stop because the computer thinks the motor is off.

 

I agree with th_racer. I had a Chevy that did the same thing. It was almost like the truck didn't have any oil in it. Every electrical function went to he**, A/C didn't work, jerked around would barely run. I would think on the Cummins the crankshaft position sensor should be easy to replace. I have only owned my truck about two years. I figured I should learn something about it if I may being driving to 500K. This is great site for info. The Dodge/Cummins combo seems to be a good truck so far.

cjthor

01, HO, 6sp, ext cab lng box, 4x4, 78,000 miles.

 

Sounds like the engine speed sensor, first check/clean it's connection under the upper radiator hose. When the sensor dies or it's wiring is bad it will tell the pcm that the engine is not running, everything goes haywire then.

 

Thanks for the replies guys
We just got home from work tonight and hope to get a early start on it in the morning. I will post any findings as they arrise.

 

Just wanted to let yah all know.
The truck went to the dealer and after a bill for 1.5hrs no resolve?
Tech says no codes and cant find anyting, but yep you got a problem
So my buddy licks his wounds and pays the $150 and limps the truck home. I went over this afternoon and helped him pull the dash apart, while reaching under the dash he bumps a wire and bingo all systems go Seems it was a bad conection from a aftermarket alarm the previous owner had installed.
The part I still dont get is how could that take down the entire dash and all its systems? and how could DC not find a problem with a dash that the only thing lit up is the CEL Anyway my buddys rattilin down the road again and still smiling.

 

Sounds about right.
My experence has been that most electronic problems are caused when someone works on the vehicle.

 

Sounds like they got into a wire that disabled the PCM or made it paranoid. It did'nt know what to do. It's called GIGO on any computer, Garbage In Garbage Out!