Air Flow Meter/Sensor: Testing and Inspection
Mass Air Flow (MAF) Sensor -G70- Checking
Special Tools and Equipment
- VAG1526A
- VAG2594A
- VAG1598/31
- VAS5051 with VAG5051/1
Test requirements:
- Coolant Temperature at least 80 °C.
- Electrical consumers switched off (radiator fan must NOT run during test).
- A/C switched off.
Checking function
- Connect VAS5051 tester and select vehicle system "01 - Engine electronics". Engine must run at idle for this. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAS 5051 Tester, Connecting and Selecting Functions" Testing and Inspection
Display on VAS5051:
- In selection -1-, click on the diagnostic function "04 - Basic setting".
Display on VAS5051:
1 - Enter display group Max. input value = 255
- Select function "002" in button field -2- for "display group number 002" and press Q button to confirm input.
Display on VAS5051:
- Check specified values for load detection in display fields -3- and -4-.
Display Group 002:
If specified value is obtained:
- End function "04 - Basic setting" by pressing <- button.
Evaluation display group 002
Display Group 002:
Voltage Supply For Mass Air Flow (MAF) Sensor, Checking
Test requirements:
- Fuse for Mass Air Flow (MAF) sensor OK
- Fuel Pump (FP) relay OK. Testing and Inspection
NOTE: Voltage is supplied to Mass Air Flow (MAF) sensor from Fuel Pump (FP) relay.
- Disconnect connector from Mass Air Flow (MAF) sensor.
- Connect multimeter for voltage measurement as follows.
- Operate starter briefly (engine can also start).
- Specification: approx. battery voltage
If specified value is not obtained:
- Check wire connection from terminal 2 of connector to Fuel Pump (FP) relay via fuse for open circuit and short circuit to Ground (GND):
- Repair open circuit or short circuit if necessary.
- Connect multimeter to terminal 2 and terminal 3 of connector for voltage measurement.
- Operate starter briefly (engine can also start).
- Specification: approx. battery voltage
NOTE: Ground (GND) from the ECM is present at terminal 3 of connector.
If specified value is not obtained:
- Check wire connections.
- Connect multimeter to terminal 3 and terminal 4 of connector for voltage measurement.
- Specification: about 5 V
If specified value is not obtained:
- Check wire connections.
Check wire connections for Mass Air Flow (MF) sensor
NOTE: Signal wire is also checked during wire test.
- Connect VAG1598/31 test box at wiring harness to Engine Control Module (ECM), do not connect ECM. Refer to "Scan Tool Testing/Wire and Component Testing Using VAG1598/31 Test Box" Testing and Inspection
- Check the following wire connections for open circuit and short circuit to Ground (GND) and B+:
- Repair open circuit or short circuit if necessary.
- Also check all wires for short circuit to each other.
If wire connection is OK:
- Replace Mass Air Flow (MAF) sensor -G70-.