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.