Air Mass Meter Test
CAUTION:
When disconnecting air duct outlet from air mass meter, do not allow "O" ring to fall into inlet side of air mass meter.
- Start and run engine until cooling fan cycles. Stop engine and disconnect air duct outlet from air mass meter. Start engine and increase engine speed to over 2500 RPM.
- Turn ignition off. After 4 seconds, observe air mass meter inlet for a one second glow of hot wire. If glow does not occur, go to step 3). If glow occurs, but system is still operating in limp-home mode, the air meter and ECU should be checked by substituting known good units, one at a time. Proceed to FUEL INJECTION BASE LINE VALUE adjustment.
- Pull air mass meter connector boot back (do not unplug connector). Connect voltmeter positive lead to pin No. 1 and negative lead to pin No. 4, from rear of connector. See Fig 1 .
- Start and run engine until cooling fan cycles. Start engine and increase engine speed to over 2500 RPM. Allow engine to return to idle. Stop engine and observe voltmeter for a 1-second, 4-volt reading.
- If voltage is okay, replace air mass meter and proceed to FUEL INJECTION BASE LINE VALUE adjustment. If voltage is not present, verify correct wiring between air mass meter and ECU by checking for continuity between air mass meter pin No. 4 and engine ground at lifting hook. Also verify that continuity is present between air mass meter pin No. 1 and ECU harness connector pin No. 8.
- If wiring is okay, start engine and check for battery voltage between pin No. 2 (positive lead) and pin No. 4 (negative lead) of air mass meter. Stop engine. Repair wiring if necessary.NOTE: The following checks are to be made with the air mass meter and ECU harness connectors unplugged. The ignition must be off when connecting or disconnecting the ECU. Repair any problems as they are found before proceeding to next step in test procedure. Always probe from rear of each connector to avoid enlarging connector pin holes.
- Place a jumper wire across pins No. 3 and 6 of air mass meter connector, and check for continuity between pins No. 6 and 7 of ECU harness connector. Place a jumper wire across pins No. 5 and 6 of air mass meter connector, and check for continuity between pins No. 6 and 14 of ECU harness connector.
- If wiring checks okay, air meter and ECU should be checked by substituting known good units, one at a time. If any unit is found defective, and replaced, proceed to FUEL INJECTION BASE LINE VALUE adjustment.