Mass Air Flow Sensor, Checking
MASS AIR FLOW SENSOR, CHECKING
Special tools, testers and auxiliary items
- VAG 1551 Scan Tool (ST) or vehicle system tester VAG 1552 with VAG 1551/3 adapter cable
- VAG 1598/18 test box
- Multimeter (Fluke 83 or equivalent)
- VW 1594 connector test kit
- Wiring diagram
Test conditions
- Electrical consumers switched off (radiator coolant fan must not run during the check)
- Air conditioner switched off
Test sequence
- Start engine and run at idle speed.
- Connect VAG 1551 scan tool (VAG 1552) and insert "Engine Electronics" address word 01. Carry out selection at idle, refer to "On-Board Diagnostics II With VAG 1551". Testing and Inspection
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08.
- Press -Q- button to confirm input.
Indicated on display
Read measuring value block HELP
Input display group number XXX
- Press -0-, -0- and -1- to input display group number 001.
- Press -Q- button to confirm input.
Indicated on display (1, 2, 3 and 4 = Display fields)
Read measuring value block 1 ->
1 2 3 4
NOTE: If something different is indicated on the display:
See Scan tool operating instructions.
CAUTION! Do not continue with the check until engine coolant temperature exceeds 80 °C (display field 2).
- Press -C- button.
- Press -0-, -0- and -3- to input display group number 003.
- Press -Q- button to confirm input.
Indicated on display (1, 2, 3 and 4 = Display fields)
Read measuring value block 3 ->
1 2 3 4
- Check engine load signal in display field 2.
Specification: 0-5%
If the specification is not attained or the value remains constant when revving-up:
- Continue check according to following table.
Checking Voltage Supply
- Separate 4-pin connector to MAF sensor.
- Connect multimeter to measure voltage at connector terminals 1 and 3.
- Switch ignition on.
Specification: Min. 9 volts
- Switch ignition off.
- Reconnect MAF sensor harness connector.
If no voltage is present:
- Check wiring according to wiring diagram.
Checking wiring
- Connect VAG 1598/18 test box to ECM wiring harness.
- Check wiring for open circuits between test box and 4-pin connector, according to wiring diagram.
- Terminal 2 and test box socket 16
- Terminal 4 and test box socket 17
- Wire resistance: Max. 1.5 Ohms
- Check wires at 4-pin connector for shorts to one another.
- Terminal 2 and test box socket 17
- Specification: Infinity Ohms (no continuity)
- Check wiring at 4-pin connector terminals 2 and 4 for short circuit to battery positive voltage (B+) according to wiring diagram.
If no wiring malfunction is detected:
- Replace MAF sensor G70.