GM Service Manual Online
For 1990-2009 cars only

Circuit Description

This diagnostic test checks for the loss of or invalid Heater and A/C (HVAC) programmer serial data to the PCM. When such a condition exists for 11 seconds, DTC P1605 is set.

Conditions for Setting the DTC

Test Conditions

    •  DTC P0322 not set.
    •  Engine speed 500 RPM or more for 10 seconds continuously.

Failure Condition

Invalid or no serial data from the HVAC programmer to the PCM for 11 seconds.

Action Taken When the DTC Sets

    •  The Malfunction Indicator Lamp (MIL) will not illuminate.
    •  No message will be displayed.

Conditions for Clearing the DTC

    •  A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
    •  A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
    • Use a scan tool to clear DTCs.
    • Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

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Go to ECC System Check in Section 1

Go to A Powertrain On Board Diagnostic (OBD) System Check