| WARNING | Read service precautions before proceeding with service procedure. See SERVICE PRECAUTIONS . |
| CAUTION | If Engine Control Module (ECM) replacement is instructed in following test, always ensure ECM electrical connectors and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. |
Circuit Description
Mass Airflow (MAF) meter uses a platinum hot wire which is maintained at a constant temperature by controlling the current flow through the hot wire. Current flow is then measured as an output voltage. MAF meter may also be referred to as airflow meter. DTC is set when ECM detects an open or short in MAF meter circuit for more than 3 seconds with engine speed at 3000 RPM or less. If DTC P0100 exists, ECM will operate in fail-safe mode which keeps ignition timing at 5 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 or shorted, or power source circuit may be open. If MAF meter air flow rate is 271.0 gm/sec. or more, EVG 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.