94 6.5TD HD engine

[PVSLS400]

Hey guys!

I am fairly new to this forum and appreciate this site much. I have searched and searched but have a issue with my 94 6.5 TD HD Rollback Tow Truck. first issue is speedo goes wild all the time i will have cruse control on and truck will stay the same speed but speedo still goes wild, 2nd issue is will be going down highway the service trottle soon light and check engine light flash at the same time, will lose power but if i tap on accelerator a few times it will resume power and everything is fine. I have replaced injection pump last year and did the pmd and relocated it with the kit from FSD. I pulled codes and am getting a code 12? which my mechanic says is not a valid code any news i missed here?

Thanks
Josh

[a5150nut]

Code 12 means everything is good with the check system.

Might try cleaning electrical connections going to the dash cluster and on the VSB just inside the dash. Remove the glove box and its on the left side of the opening. White plastic case the size of a pack of cigarettes. Clean these connections too. Then down to the trans/transfer case to the sending unit. You can get a can of spray contact cleaner at Rat Shack. If that doesn't clear things up, there is a test sequence in the manual to trouble shoot the spedo system.

Instead of paying mecanic to read codes, use a paper clip or shot wire in the plug under the steering colum. Two uper, right conectors as you look at it. Then turn on the ignition and count the flashes of the SES light. one, one two, one, one two, one, one two is your twelve code. Any others would be one two three, one two three four = 34 code, ect. Write them down and usualy correct the first one, then clear and test run and check again. Sometimes one fault will cause others - reson for correcting first ones then checking again.

And, WELCOME to TDP!!

[daustin]

Welcome to the 'page. If cleaning all the contacts dosen't clear it up, it's either a problem with the cluster itself or the VSS sensor on the tranny. I had that problem some time ago, finally i replaced the VSS and it went away. Good luck, let us know what the final problem is.
Don

[a5150nut]

PVSLS40,
You didn't say whether your truck is 2x or 4x. Last year I had enough filing built up in my transfer case that it filled the gaps on the signal wheel under the sensor. Than filings clinging to the sensor that would cause it to loose signal at slow speeds and the ABS would think the rear wheels had quit turning and release the rear brakes. Lots of fun in stop and go traffic! :eek: