| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. |
Circuit Description
ECM uses electrical load information from body Electronic Control Unit (ECU) and A/C state from A/C ECU in order to control idle speed. DTC P1645 is set when ECM does not receive communication from body ECU and A/C ECU for 5 seconds or more. Possible causes are
- Faulty gateway ECU.
- Faulty A/C ECU.
- Communication bus.
Diagnostic Aids
Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.