| 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. |
Circuit Description
ECM uses information from body Electronic Control Unit (ECU) for electrical load and from A/C ECU for A/C state 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
- Body ECU.
- A/C ECU.
- Communication bus.