Test Description

The numbers below refer to the step numbers in the diagnostic procedure.

1. 2
   
   Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 3
   
   Determine if the instrument cluster or Engine Control Modules (ECM) have DTCs set which may affect engine cooling operation.
3. 4
   
   The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.