My speedometer completely stopped working at 156,800 miles. The gauge itself was ruled out as the problem since reading vehicle speed from the ECU via OBDII also read 0 MPH. I replaced the Transmission Output Speed Sensor (a very inexpensive part) to make sure that wasn't the issue, and also checked the wire harness continuity from the sensor connector to the ECU connector. My belief is that there was a bad pin on the ECU for this signal. A further error this can cause is the Idle Air Control High RPM code, since the computer cannot tell the car is moving with the throttle closed and will think the engine RPM being high is a result of an IAC problem and not simply that the engine is being turned faster by the transmission. I purchased a "refurbished" ECU on eBay and (eventually, got a few bad units) this fixed the problem. I think that, in general, the ECU has issues with poor connectivity to the pins, which can cause all sorts of very strange and frustrating problems.
A D V E R T I S E M E N T S
My speedometer completely stopped working at 156,800 miles. The gauge itself was ruled out as the problem since reading vehicle speed from the ECU via OBDII also read 0 MPH. I replaced the Transmission Output Speed Sensor (a very inexpensive part) to make sure that wasn't the issue, and also checked the wire harness continuity from the sensor connector to the ECU connector. My belief is that there was a bad pin on the ECU for this signal. A further error this can cause is the Idle Air Control High RPM code, since the computer cannot tell the car is moving with the throttle closed and will think the engine RPM being high is a result of an IAC problem and not simply that the engine is being turned faster by the transmission. I purchased a "refurbished" ECU on eBay and (eventually, got a few bad units) this fixed the problem. I think that, in general, the ECU has issues with poor connectivity to the pins, which can cause all sorts of very strange and frustrating problems.
- John W., Spokane, WA, US