Possible causes

– Weak battery
– Faulty Transmission Control Module (TCM)
– Harness is open or shorted between (TCM) and Engine Control Module (ECM)
– Poor circuit electrical connection between (TCM) and (ECM)

Tech notes

There is a service bulletin for the 2001 Infiniti I30.

2001 Infiniti I30 Factory Service Bulletin OBDII Code P1605

When is the code detected?

Malfunction is detected when an incorrect signal from Transmission control module (TCM) is sent to Engine Control Module (ECM).

Symptoms

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

P1605 INFINITI Description

The malfunction information related to Automatic Transmission is transferred through the line circuit from Transmission control module (TCM) to Engine Control Module (ECM).

INFINITI Technical Service Bulletins for P1605 code