| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. |
Circuit Description
MAF sensor uses a platinum hot wire maintained at a constant temperature. Airflow past sensor affects temperature and current flow through sensor. DTC is set when ECM detects an open or short circuit with engine speed of 4000 RPM or less. ECM will operate in fail-safe mode if DTC P0100 is set. Possible causes are
- MAF open or short circuit.
- MAF sensor.
- ECM.
Scheme 16
- Connect scan tester to DLC3 connector. see scheme 1 Start vehicle engine and allow to idle. Turn on scan tester. Monitor MAF flow rate. If scan tester reading is 0.0 gm/sec., go to next step. If reading is 439 gm/sec. or more once engine is at normal operating temperature, go to step 5).
- Disconnect MAF sensor connector. Ensure ignition is on. Using DVOM, measure voltage between terminal No. 1 (Yellow/Red wire) and ground. (Scheme 17) If voltage is 9-14 volts, go to next step. If voltage is not 9-14 volts, check for an open circuit in wiring harness between EFI main relay and MAF sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
- Access ECM behind right instrument panel speaker. Start engine. Backprobing ECM connector, measure voltage between ground and terminal No. 2 (Green wire) at ECM E5 connector. (Scheme 18) If voltage is 1.1-1.5 volts, replace ECM and retest.
- If voltage is not 1.1-1.5 volts, check for open or short circuit between MAF and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, replace MAF sensor and retest.
- Access ECM behind right instrument panel speaker. Turn ignition off. Using ohmmeter, backprobe ECM connector. Check continuity between ground and terminal No. 16 (Brown wire) at ECM E5 connector. (Scheme 18) If continuity does not exist, replace ECM and retest. If continuity exists, check for open circuit between MAF sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, replace MAF sensor.
