Circuit Description

WARNING: This page is about a different car, the 2003 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.

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 body ECU.
Faulty A/C ECU.
Faulty communication bus.