| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM connectors 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. If DTCs P0100, P0101, P0110, P0115 and P0120 are output together, check circuit E2 (White wire) between terminal No. 18 at ECM harness connector E8 and splice E7. Repair as necessary. See WIRING DIAGRAMS article.
Note. For component location, see appropriate illustration in THEORY & OPERATION article.
Circuit Description
Mass Airflow (MAF) meter uses a platinum hot wire maintained at a constant temperature. Airflow past meter affects temperature and current flow through MAF meter. DTC is set when ECM detects an open or short in MAF meter circuit for more than 3 seconds with engine speed at 4000 RPM or less. If DTC P0100 exists, ECM will operate in fail-safe mode in which ignition timing is fixed at 10 degrees BTDC. Possible causes are
- MAF meter circuit is open or shorted.
- Defective MAF meter.
- Defective ECM.
Diagnostic Aids
After confirming DTC P0100, use Toyota hand-held tester or scan tool to access CURRENT DATA to confirm MAF meter air flow rate. If MAF meter air flow rate is 0.0 gm/sec., VG circuit may be open and shorted, or power source circuit may be open. If MAF meter air flow rate is 271.0 gm/sec. or more, E2G circuit may be open. Using hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.