Dash stopped working, set P0500 code (Speed sensor)

[fathead]

Greetings to all

New to the forum, hope you can help me with my problem. 2003 Vibe base with no ABS. Dash quit on the way home, then check engine light came on. Drove home and started the car the next day, dash was working but engine light still on. Checked for codes using a cheap code reader, code came up P0500, VSS (Vehicle speed sensor A). Cleared codes and car was fine for two weeks. Then the dash quit again and was fine the next day. Now the dash has quit for good for a week now. Tried a new cluster from other Vibe, same thing, not working. All that was working were the signals, door light, airbag light, high beam light, oil and alt lights. Even the dash did not light up and no mileage too. No tach, speed, temp or fuel gauge were working, just the needle gauges where lite up reading zero. I did try a new speed sensor, same thing, no dash. The P0500 code came back, also when the dash quit, transmission shifted funny because of no signal to the speed sensor. Tried a high end scanner(Autel and Launch scanner) and it won't communicate with the PCM. Tried a used PCM and the same thing, no communication and no dash. Check for power at the OBDII port, have power and have signal and communication ground. All fuses are good at the two fuse boxes. At my wits end trying to find the problem. Would be very grateful if you can give me some insight on my problem. Thanks so much.

[andrewclaus]

Check the wiring harness to the VSS.

[jolt]

As for the scanners, I have a Launch 129 (I think that's the model), and it does not work under GM. It does work under Toyota Matrix so you may try that. First thing is to un-plug connectors, check wiring, and re-seat connectors as andrewclaus refers too. Check wiring at ECM for power (voltage). Make sure ECM is grounded good to the engine and chassis. Add another ground wire if not sure about it as you can never have to may grounds. Bad grounding can cause all kinds of weird electrical issues so rule the grounding out first.