Intermittent speedo operation.

Check engine light on.

This has been an issue for some time. A new speed sensor and second hand PIM fitted by local Holden dealer.

Straight after starting the vehicle the speedo will either work or not. Only after clearing the codes will the speedo come back on line.

The code is always logged in the PIM but not always in the ECU.

Can clear code while still running and speedo comes back on line.

Using a pulse generator can drive the speedo from the sensor wires with a square waveform and it has never had an issue when doing this.