P1605

Diagnostic Chart:

Refer to Data Link Communications Schematic.

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) uses the Class II Serial Data circuit to communicate with various other devices and systems in the vehicle. The PCM ensures that communication remains established by monitoring the Class II serial data circuit for state of health messages from the other devices using the circuit. If the PCM detects a loss of the state of health serial data message from the HVAC controller, DTC P1605 will be set.

CONDITIONS FOR RUNNING THE DTC
^ The ignition is ON.
^ System Voltage is greater than 8.2 volts.

CONDITIONS FOR SETTING THE DTC
The PCM is detecting a loss of serial data from the HVAC controller for longer than 5 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
^ The PCM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data.

CONDITIONS FOR CLEARING THE MIL/DTC
^ A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

DIAGNOSTIC AIDS
Inspect for the following conditions:

IMPORTANT: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

^ Poor terminal connection - Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension.
^ Damaged harness - Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault.
^ PCM and engine grounds for clean and secure connections

If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.