P1605 - FAULT CODE - OBD2

P1605 BUICK, CADILLAC, CHEVROLET, GMC: LOSS OF SERIAL HVAC DATA

HVAC (Heating, Ventilation, and Air Conditioning) is a system used to control the temperature inside the car. It regulates it to provide comfort to its occupants. This system is in charge of the air conditioning and heating system.

The HVAC system is continuously monitored by the PCM (Powertrain Control Module) to check the best performance. If this controller notices valid or non-serial data from the VVAC module for a period longer than 11 seconds, the fault code P1605 OBDII will be set.

• Check Engine light ON.
• Wrong operation of the air conditioning.
• Constant changes in the fan air temperature.

These are the reasons for setting the P1605 OBD2 diagnostic code:

• The HVAC system module harness may be faulty.
• The HVAC electrical connections could be damaged, which can result in a short circuit.
• Possibly, the HVAC module is in poor condition.

To troubleshoot the DTC P1605 OBDII code, make this:

• Consult the Technical Service Bulletins. These provide direct guidance from the manufacturer.
• Use an automotive scanner to check if other DTCs related to the climate control system are stored. Diagnose the codes according to the order shown on the tool.
• Verify that there are no bad wires or connectors in the HVAC system If you discover common deficiencies due to corrosion, wear, tear, burns, make the necessary repairs.
• Measure the circuit voltages of the HVAC module, and check that they match those indicated by the manufacturer on the vehicle's information source. If you detect big differences, make the appropriate adjustments.
• If after performing the above checks you still get the P1605 code, there may be a bad HVAC control module.