Refer to Data Link Connector Schematics in Electrical Diagnosis.
Circuit Description
The powertrain control module (PCM) uses the class 2 serial data circuit to communicate with various other devices and systems in the vehicle. The PCM ensures that communication remains established by monitoring the 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 is set.
Conditions for Running the DTC
| • | The ignition is on. |
| • | The system voltage is more 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 stores the conditions which were present when the DTC set as Fail Records data only.
Conditions for Clearing the MIL/DTC
| • | A history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC may be cleared using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
Diagnostic Aids
An intermittent may be caused by a faulty connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect for the following conditions:
| • | An intermittent short circuit on the serial data circuit. Refer to Wiring Repairs in Wiring Systems. Test all of the related wiring for an intermittent short to ground or short to voltage. |
| • | Inspect the PCM and the affected control module harness and related connectors for improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. |
| • | Inspect the wiring harness for damage. Test for an intermittent short or open circuit in the wiring harnesses related to the affected control module, including the ignition positive voltage, battery positive voltage, ground, and serial data circuits. |
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the conditions.
Test Description
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Important: If a loss of DLC data has already been diagnosed using the DLC Diagnosis table, clear this DTC and continue diagnosis with the Powertrain OBD System Check. Attempt to select HVAC Data on the scan tool. Can the HVAC Data be displayed? | -- | Go to Diagnostic Aids | |
3 |
Was a problem found? | -- | ||
4 |
Was a problem found? | -- | ||
5 |
Was a problem found? | -- | Go to Functional Check in HVAC System - Manual | |
6 |
Does the scan tool indicate DTC P1605 failed? | -- | System OK |
