1-2-1 (MAF Signal Absent Or Faulty)
- Connect measuring unit to fuel injection ECU. See MEASURING UNIT
under SELF-DIAGNOSTIC SYSTEM. To check Mass Airflow (MAF) sensor signal, turn ignition on. Connect voltmeter between measuring unit terminals No. 13 and 20. About 2.7 volts should be present. Start engine. About 3.5 volts should be present at idle with engine hot. Turn engine off. If voltages are okay, go to step 3) and check MAF sensor ground circuit. If voltages are not okay, go to next step.
- Turn ignition on. Connect voltmeter between MAF sensor connector terminal No. 4 and ground. See Fig 1
. Voltage should be about 2.7 volts. Start engine. Voltage should be about 3.5 volts during idle with engine hot. If voltages are correct, check voltage supply for an open or short circuit. If voltages are incorrect, go to next step and check MAF sensor ground circuit.
Courtesy of VOLVO CARS OF NORTH AMERICA.
- Turn ignition off. Connect ohmmeter between MAF connector terminal No. 2 and ground, then between connector terminal No. 1 and ground. See Fig 1
. Ohmmeter should indicate about zero ohms in both instances. If reading is okay, go to step 5). If reading is incorrect, go to next step.
- Ensure ignition is off. Connect ohmmeter between measuring unit terminals No. 20 and 8, then between terminals No. 20 and 12. Ohmmeter should indicate about zero ohms in both instances. If reading is incorrect, repeat test using new fuel injection ECU. If reading is correct, go to next step and check MAF sensor voltage supply.
- Turn ignition on. Connect voltmeter between ground and MAF sensor connector terminal No. 3. See Fig 1
. Voltmeter should indicate battery voltage. If voltage is not present, check for an open or short circuit in voltage supply. If voltage is present, repeat test using new MAF sensor.