Possible causes

– Faulty Engine Control Module (ECM)
– ECM harness is open or shorted
– ECM circuit poor electrical connection
– ECM Programming

Tech notes

Check the ECM fuse, if fuse is OK try erasing the code first and if the code comes back you may have to reprogram or replaced the ECM.

When is the code detected?

Indicates the Engine Control Module (ECM) has experienced an internal memory fault.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0657 TOYOTA Description

The Engine Control Module (ECM) continuously monitors its internal memory status, internal circuits, and output signals to the throttle actuator. This self?check insures that the ECM is functioning properly. If any malfunction is detected, the ECM will set the code and illuminate the engine light.