| CAUTION | If ECM replacement is instructed in following tests, always ensure ECM connectors and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. |
Note. For component location, see appropriate illustration in THEORY & OPERATION article.
Circuit Description
Constant battery voltage is supplied to BATT terminal at ECM as the back-up power source. DTC is set when open in back-up power source is detected. Possible causes are
- Back-up power source circuit is open.
- Defective ECM.
Diagnostic Aids
If DTC P1600 exists, the ECM will not store any other DTCs. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.