Bert Duursma

Dear Bill,
Adrian is right. According to my findings now and to technical 964 doc the DME only detects a broken wire (on the engine temp sensor) and does not check upper and lower limits. In case a tempsensor wire is broken the DME assumes a value of 120C engine temperature, which is ok to bring the car home without problems.

Adrian

I could not remember the word yesterday but the original DMEs had what was called "plausibility detection" a really fancy silly word for tolerance detection. This was removed because it was really unreliable and fired up many faults. Hence the requirement to read the DME during a service. When the check engine light was introduced with the first of the 964 series of DME the light would flash on and off with these faults. So it was removed.
Now the DME will only detect hard failures and not what we call soft failures.
Ciao,
Adrian
964C4