Test Description

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The numbers below refer to the step numbers on the diagnostic table.

3. 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.
5. Determine if the Rear Seat Audio (RSA) Control Module, HVAC Control Module, Body Control Module or Powertrain Control Module have set DTCs which may affect HVAC operation are present.
6. The presence of DTCs which begin with "U", except U1500, indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed. Be sure to diagnose all other "U" codes before diagnosing a U1500.
7. Answer Yes if the first three characters of the DTC name begins with B10; regardless of the last two characters.

Fig 1: Diagnostic System Check - HVAC Systems - Automatic (Step 1 To 6)
Courtesy of GENERAL MOTORS CORP.

Fig 2: Diagnostic System Check - HVAC Systems - Automatic (Step 7 To 9)
Courtesy of GENERAL MOTORS CORP.