Got a 99 4.6 4x4 no speedo or odometer. All sensors are working can read speed thru a scanner on the obd port. Loosing signal somewhere between pcm and instrument cluster. Can not find any wiring diagrams of the signal wires. Even the ford dealer was clueless couldn't tell me more than I already knew and still charged 300. any schematics or advice would be greatly appreciated.

 

The diagnostic test at a Ford dealer is pretty straight forward. Hook up the scan tool, run the test, analyze the results. It's going to be either the PCM or the cluster, usually, if you can read VSS data from the PCM.

The data is exchanged between the PCM and cluster via the SCP network, not individual signal wires. If the engine starts on a 99, the SCP network is operational.

 

According to ford everthing checks out I can take this cluster stick in my expedition everything works fine take the one from the expedition and put in the truck same results. Ford wants to check each individual wire by the hour say it could run in the thousands. I work with can/bus line systems a lot more complicated than this every day, I can track all the wires my self I just need a schematic. The can lines are losing or shorting some where between the pcm and cluster im thinking possibly a low voltage feed back which cause all types of havoc on this type of system with the micro processors.

 

Then it should be working.


There are only TWO wires that comprise the SCP bus. Shouldn't take long....

If that were true, then how are only the odometer and speedometer affected without also affecting PATS and the rest of the PCM-originated items?

 

Ive got an after market speedo spliced strait to the sensor in tranny working fine. Im just going off what the computer geeks at ford said. I don't have much faith in the computer trained idiots all they know how to do is push buttons and cost money. But ican verify the only problem I have is speedo and odometer between pcm and cluster just need a schematic to ohm everthing out. From what I found today They are some low voltage back feeding on some wires just don't know if its the ones im looking for. found a few bad grounds and possible fuse block. does any one know where to find a full schematic for the f150.