Speedo And Abs Question - Diesel Forum

kingkrown · 08-04-2009, 04:30 PM

Ok here is the deal. My truck ( 2007 Ford F250 diesel 4X4 / with edge attitude) started acting funny. The speedo goes to about 5 miles an hour and the jumps to 90. The Odometer is also going fast. I replaced all 3 sensors. One in the diff and 2 in the tranny nothing worked. Then I put a new cluster in from a friends truck to try that out, still nothing. So I began to diagnose a bit more. I left the front two sensors plugged in and unplugged the rear diff. sensor. I believe this has to do with the ABS. When I unplugged it everything goes back to working fine. Only difference is ABS light comes on because it is unplugged. I thought it might be the new sensor was bad as well. Ford gave me another and it did not work either. So now I am at a loss and have no idea what it could be. I am not getting any codes either. I also checked the pigtail to the diff and it is getting power as well. Please send me some help. Ford wants to just keep throwing parts at thousands of dollars. HELP HELP HELP

GrampyJim · 08-04-2009, 04:59 PM

Replaced the sensors in the trans????

First things first... remove the programmer altogether... just get it out of the picture for now.... If it isn't the source of the concern, reinstall it but not until after the thing is fixed.

Next... any sources of RFI (radio frequency interference) - this would include any radio receiver using a super-herterodyne tuner.. re-assess.

Still having troubles? Compare the signals from all three wheel speed sensors - this will require a fairly talented scan tool.. Check for any "noise" on the wheel speed sensor circuits at the same time. The module that receives VSS (this is the rear axle signal) would rather use that signal rather than infer vehicle speed from one of the front wheel speed senors - I'm surprised there isn't at least a coherency code.... (the ABS likes it when all three sensors report the same speed).

Has any differential work been perfromed recently? Something that could have damaged the indicator ring?

FWIW, have the ABS module and the instrument cluster module been polled for DTCs? Or just the PCM?

It isn't Ford that wants to throw parts... it is some guy that calls himself a "tech" that wants to throw parts. Each and every problem has a logical diagnostic process... filling the old parts cannon and letting fly isn't logical nor is it diagnostic.

My best suggestion is to find a dealer with technicians rather than guys in coveralls. Good luck with your concern.