No Communication With Auxiliary Heater

No Communication With Auxiliary Heater:

Fault symptoms
No communication with auxiliary heater (DAH).

Conditions
The following conditions are applicable:
- Ignition switch in ON position

Diagnostic help
First, check the fuses for the DAH control module and that the data link connector pins for communication are in place.
Then, check whether the DAH is awake and allowing diagnostics communication. If not, check to see if the diagnostic tool works in another car.
If no fault is found, rectify the communications lead between DAH and the data link connector.

Check wiring harness.
Jiggle the wiring harness at several points and in different directions to detect intermittent breaks and short-circuits in the leads.
Observe the multimeter, test lamp or diagnostic tool during the test.