Electronic speedometer clipped into a '98 TranSport, but the model is really irrelevant. The speedometer and odometer are inoperative. The easy call would be a VSS problem. However, the VSS will output a solid 2.5V minimum signal at less than 3 MPH. The PCM receives the signal and displays the vehicle speed properly. It records the mileage, and operates the transaxle and TCC correctly. However, the speedometer still fails to indicate. The owner has changed the speedo head with a used one with no change. The speedo electronics are presenting 5.01V to the PCM for switching. I checked VSS output signal at C210 and directly at PCM. The signal frequency/duty cycle is correct, but amplitude is only about 6mV regardless of whether the speedometer load is present or not. Further, the speedometer indicates speed and displays an odometer change if that signal is grounded at 6-10Hz.
PCM Speed Data:
PCM - Speedometer signal sinking output waveform:
Can someone tell me what the problem might be if not the PCM sinking output? I'm all ears...
I'm just trying to justify replacing an otherwise fully functional PCM.
