| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES - IMPORT article in GENERAL INFORMATION, or appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT. |
Note. For component location, see appropriate illustration in THEORY & OPERATION article.
Circuit Description
ECM receives the operating condition of A/C system from the A/C Electronic Control Unit (ECU) and electrical load information from the body Electronic Control Unit (ECU) over the bus communications system. ECM uses this information to control engine idle speed. Possible causes are
- Defective body ECU.
- Bus communications circuit is open or shorted.
- Defective ECM.
Diagnostic Aids
Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.