Mass Airflow Sensor: Test
- Disconnect MAF sensor from air cleaner housing and position far enough back so that burn-off process can be observed. See Fig 1.
- Start engine and let idle above 2000 RPM for minimum of 3 seconds. Switch ignition OFF. Observe burn-off process. Heating wire glows for about 1 second. If NO: Position aside rubber sleeve on MAF sensor connector.NOTE: Connector must remain connected to MAF sensor.
- Connect (US 1115) LED tester to terminals No. 1 and 4. See Figure. Repeat test sequence. LED tester must light up during burn-off. If LED tester lights up, replace MAF sensor.
- If LED tester does NOT light up: Connect (VAG 1598) test box, using (VAG 1598/5) adapter cable, to ECM. See CONNECTING VAG 1598 TEST BOX .
- Connect LED tester to terminal No. 26 (ground) and terminal No. 25. See Figure.
- Repeat test sequence and observe LED tester. LED tester must light up during burn-off. If LED tester does NOT light up, replace ECM. After replacement of ECM, see ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article.
- If LED tester lights up, check for continuity (and also shorts to ground), between terminal No. 4 of MAF sensor connector, and terminal No. 25 of test box. See Figure and Figure . Resistance must be 0.5 ohm maximum.
- Locate and repair, as necessary, shorts/opens in circuit wiring between MAF sensor connector terminal No. 4, and ECM terminal No. 25.
NOTE:
Do not disconnect the intake air hose or the MAF sensor harness connector.