nafaniya

[nafaniya]

speedometer problems

1999 expedition. Speedometer on and off. oss was replaced(no luck ) codes p0720, p0141, p0161. Suspect pcm. Please help! I use to be professional mechanic about 20 years ago )) , but now i am out of date)))

 

[Thermo]

nafaniya, based on what you are describing, you are having a problem with the wiring harness that feeds both of the downstream O2 sensors and the VSS/OSS sensor. I would tell you to get under the truck and look at the sides of the tranny to find the wiring harness (should be on driver's side). Now, follow it forward towards the motor. Where it comes in close contact to the exhaust piping, inspect the wiring very closely. I bet you will find that the wiring harness got loose and touched the exhaust pipes, leading to the insulation melting, leading to your issues.