P38A Engine speed sensor fault and faulty temperature gauge.fauf

Finally got my P38 running after new timing chains, head gasket, radiator and replacement injection pump.

Faults now logged are engine speed sensor fault. This occurs after blipping the accelerator and revs fail to drop for a few seconds. Any clues anybody.

Also fault with temperature gauge. Where is the temperature sensor on the M51. Will check to see if it has been disconnected!

The temp sensors are in the head under the inlet manifold.

There are 2 temperature sensors, one near the front the other in the middle, 1 for the ECU and the other for the gauge. I can never remember which is which.

ShaunPDisco said:

Finally got my P38 running after new timing chains, head gasket, radiator and replacement injection pump.

Faults now logged are engine speed sensor fault. This occurs after blipping the accelerator and revs fail to drop for a few seconds. Any clues anybody.

Also fault with temperature gauge. Where is the temperature sensor on the M51. Will check to see if it has been disconnected!

Click to expand...

Would that not be the CPS sensor?

Front temp sensor adjacent to injection pump is gauge sensor. Either brown (one wire) or blue (two wire) depending if AC is fitted. Next one (Green) between cylinders three and four is ECU temp sensor. On later models (1999 and on) an additional sensor (Black) is fitted between cylinders five and six to signal use of AC fans to assist cooling in case of overheat. Engine speed sensor is indeed CPS. If you remove CPS to check, only remove it from bracket it sits on DO NOT remove bracket itself.

Thank you Gents.

I had previously changed the CPS but that was now a long time ago! Don’t think I removed the bracket previously so will do again.

Will let you know if it works!

ShaunPDisco said:

Thank you Gents.

I had previously changed the CPS but that was now a long time ago! Don’t think I removed the bracket previously so will do again.

Will let you know if it works!

Click to expand...

Odd really. Some people seem to keep replacing it and it is one part I've never touched. That's probably the kiss of death!