Troubleshooting

DTC P1646 Transmission Control ECU Malfunction

CIRCUIT DESCRIPTION

DTC Detection Condition:

The transmission control ECU communicates whether its operation is normal or not to the ECM using this line. When the transmission control ECU is operating normally, it sends a constant pulse signal to the ECM.

Wiring Diagram:

Step 1:

Step 2 - 3:

INSPECTION PROCEDURE

HINT:
- If DTCs UOOO1 and P1646 are output simultaneously, the fail-safe function operates to stop the engine. At this time the transmission control system may be abnormal.
- Read freeze frame data using the hand-held tester or the OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, this is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.