| 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 - IMPORT article in GENERAL INFORMATION. |
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
- Faulty body 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.