Mass Air Flow Sensor, Checking
Use only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) Sensor -G70-.
Special tools and workshop equipment required
- Multimeter.
- Wiring diagram.
Test requirements
- The Mass Air Flow (MAF) Sensor -G70- fuse OK.
- Battery voltage at least 12.5 volts.
- All electrical consumers such as, lights and rear window defroster, switched off.
- Vehicles with automatic transmission, shift selector lever into position "P" or "N".
- A/C switched off.
- Ground (GND) connections between engine/transmission/chassis OK.
- Coolant Temperature at least 80° C.
- Ignition switched off.
Test procedure
-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .
Start diagnosis
-- Connect the scan tool.
-- Start engine and let it run at idle.
-- Using the scan tool, Check the air flow quantity of the Mass Air Flow (MAF) Sensor -G70- at idle:
| Diagnostic text | Specified value | |||
|---|---|---|---|---|
| Air flow quantity at Mass Air Flow (MAF) sensor | ||||
|
2.00 to 5.00 g/sec | |||
-- End diagnosis and switch ignition off.
If specified value was not obtained:
Checking voltage supply
-- Disconnect the Mass Air Flow (MAF) Sensor -G70- electrical harness connector -1-.
-- Start the engine and let it run at idle.
-- Using a multimeter, check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminal 2 to engine Ground (GND).
Specified value: battery voltage.
-- Switch the ignition off.
If specified value was not obtained:
-- Check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminal 2 to the Power Supply Relay (terminal 30, B+) -J317- terminal 6/87 for an open circuit.
Specified value: 1.5 Ω max.
If the specification was not obtained:
-- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
-- If necessary, repair the faulty wiring connection.
Checking 5 volt reference
-- Start the engine and let it run at idle.
-- Using a multimeter, check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminal 3 to engine Ground (GND).
Specified value: 5V
-- Switch the ignition off.
If specified value was not obtained:
-- Check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminal 3 to the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248- electrical harness connector T80/4 for an open circuit.
Specified value: 1.5 Ω max.
If the specification was not obtained:
-- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
-- If necessary, repair the faulty wiring connection.
If no malfunction is detected in the wiring and if the voltage supply was OK:
Checking Ground (GND)
-- Using a multimeter, check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminal 5 to engine Ground (GND) for resistance.
Specified value: 1.5 Ω max.
If the specification was not obtained:
-- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
-- If necessary, repair the faulty wiring connection.
If no malfunction is detected in the wiring and if the voltage supply was OK:
Checking wiring
If the manufacturers test box is being used, perform the following step.
-- Install the test box. Refer to 68 PIN TEST BOX ADAPTER, INSTALLING .
If the manufacturers test box is not being used, perform the following step.
-- Remove the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-. Refer to ENGINE CONTROL MODULE, REPLACING .
-- Using a multimeter, check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminals to the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248- electrical harness connector T94 for an open circuit.
| Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminals | Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248- electrical harness connector T94 terminals or test box socket |
|---|---|
| 3 | 4 |
| 4 | 50 |
| 5 | 52 |
Specified value: 1.5 Ω max.
If the specification was not obtained:
-- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
-- If necessary, repair the faulty wiring connection.
If no malfunction is detected in the wiring and if the voltage supply was OK:
-- Replace Mass Air Flow (MAF) Sensor -G70-.
-- Erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
-- Perform a road test to verify repair.
If the DTC does not return:
Repair complete, Generate readiness code. Refer to READINESS CODE .
-- End diagnosis.
If the DTC does return and no malfunction is detected in the wiring and the voltage supply was not OK:
-- Replace the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-. Refer to ENGINE CONTROL MODULE, REPLACING .
Final procedures
After the repair work, the following work steps must be performed in the following sequence:
- Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
- If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
- If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .
End of diagnosis.