Circuit Description
The PCM uses the 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 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 stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.
Conditions for Clearing the MIL/DTC
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The history DTC clears after 40 malfunction free warm-up cycles. |
| • | The PCM receives a clear code command from the scan tool. |
Diagnostic Aids
Check for the following conditions:
Intermittent short circuit on the serial data circuit.
Refer to Diagnostic System Check - Data Link Communications and check all related wiring for an intermittent short to ground or short to voltage.
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. Refer to Intermittents and Poor Connections Diagnosis , and Connector Repairs Wiring Systems. |
| • | Damaged harness. |
| Inspect the wiring harness for damage. If the harness appears to be OK, observe the sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the sensor display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems. |
| • | Inspect the PCM and the engine grounds for clean and secure connections. |
If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain on-Board Diagnostic (OBD) System Check performed? | -- | ||
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 On Board Diagnostic (OBD) System Check . Attempt to select HVAC data with the scan tool. Can the HVAC data be displayed? | -- | ||
3 |
Was a problem found? | -- | Go to Diagnostic Aids | |
4 |
Was a problem found? | -- | ||
5 |
Was a problem found? | -- | ||
6 |
Does the scan tool indicate DTC P1605 failed? | -- | System OK |
