1996 f150, 5.0, 4R70w. Code was P0500 (vehicle speed sensor a circuit)
Ive changed the VSS on the tail shaft, the sensor on the rear diff. Still same problem
. my scanner tells me my speed and rpm’s while driving but still no speedo, odometer and od light flashing. Checked all fuses and they are all good. Could it be a bad psom? I’m out of ideas.

 

Grab a DVOM and check the signals at the PSOM.

This is a very common issue, there are probably hundreds of threads with your problem. Spend a little time researching and perform some tests.

 

As bizarre as it sounds... does your dome light work? I have heard of that causing speedo issues because they are on the same circuit

 

Yea the dome light works. The third brake light is out though

 

fix the third brake light and you problems may just go away.

 

Unfortunately, the 3rd brake light out wont cause the speedometer to not work. It may mess up with the converter locking, and needs to be fixed, but it's not the main issue.

 

good to know. as my only vehicle with a third brake light is the 2021 F150, i dont know much about the issues the light being out causes other than what little i read here.

 

Is the odometer blank or just not registering any new mileage?

If it is blank then you need to verify power is getting to the PSOM, Fuse 8 and Fuse 18. If that is good, then you most likely have a failed PSOM. Look for signs of missing or burned components.

If the odometer does activate then you need to check for the VSS pulses into the PSOM.

 

Odometer is just blank

 

Here is a diagram of the VSS circuit including the PSOM:

 

That rear axel sensor in that diagram is the vss? That should be on the tail shaft of a 96 truck

 

Yes it is.


Incorrect. That is the Output Shaft Speed (OSS) sensor. It has nothing to do with the speedometer/odometer operation.

 

I swear the sensor on the transmission is for the transmission computer. The axle is for the Speedo/Odo/ABS.

I believe the E4OD did not have that sensor and relied on the VSS to determine that the output shaft speed was.

 

The E4OD transmission never had an OSS.

The Output Shaft Speed (OSS) sensor does feed information to the PCM. In turn the PCM uses that information as described in the diagram below. The OSS is tied to PCM Pins 6 and 84.

 

i have that issue where my odometer and speedometer don't work and my dome light it out