Air Flow Meter/Sensor: Testing and Inspection

Exhaust Gas Recirculation and Mass Air Flow sensor function can be checked via Output Diagnostic Test Mode (DTM) Function 03 and by also calling-up measuring value block 03 (Function 08). To do this, activate the Output DTM component: EGR Vacuum Regulator Solenoid valve N18 and then after exiting the Output Diagnostic Test Mode, check N18 via the -C- button.
By using this sequence, the EGR valve continues to be pulsed so that with the help of measuring value block 03 (display zone 3) the extreme values for the EGR valve/Mass Air Flow sensor can be displayed.

Special Tools, Testers And Auxiliary Items:
- VAG 1551/1552 Scan Tool with VAG 1551/3 adaptor cable
- VAG 1595/15 Test Box
- Fluke 53 multimeter (or equivalent)
- WV 1594 adaptor kit
- Wiring diagram

Test Sequence:
- Connect VAG 1551/1552 Scan Tool
- Start engine and let idle
- Press 0 and 1 buttons to select address word o1 "engine electronics"
Display will appear as shown:

Rapid data transfer HELP
select function XX

- Press 0 and 3 buttons to select Function 03 "Output Diagnostic Test Mode"
- Press Q button to enter input
Display will appear as shown:

Rapid data transfer Q
03 Output Diagnostic Test Mode

NOTE: Individual DTM components are activated for 30 seconds. Various work sequences must be carried out with the Scan Tool within this period as well as reading the displayed values. Read over the following work sequence first to familiarize yourself with the procedure.

Display will appear as shown:

Output Diagnostic Test Mode ->
start of injection valve - N108

- Press -> button
Display will appear as shown:

Output Diagnostic Test Mode ->
Exhaust gas recirculation valve - N18

- Press C button
- Press 0 and 8 buttons to select Function 08 "Read measuring value block"
- Press Q button to enter input
Display will appear as shown:

Read measuring value block HELP
Input display group number XXX

- Press 0, 0 and 3 buttons to select "display group 3"
- Press Q button to enter input
Display will appear as shown:

Read measuring value block 3 ->
840 rpm 272 mg/H 268 mg/H 54%

- Indicated on display

NOTE: The values in display zones 3 and 4 must fluctuate within the following control mode:
- Specification display zone 3
Lower range: 230 to 310 mg/stroke.
Upper range: 360 to 480 mg/stroke.
- Specification display zone 4:
Lower range: 2 to 5%.
Upper range: 90 to 95%.
Due to the slow refresh rate of the VAG 1551 Scan Tool, the displayed values can greatly vary. Ensure that the upper and lower range values in display zones 3 and 4 are obtained. Only regard the minimum or maximum values

If specifications not obtained, check Mass Air Flow sensor and EGR valve voltage supply as follows:
- Press -> button
- Press 0 and 6 buttons to select Function 06 "end data transfer"
- Press Q button to enter input
- Switch OFF ignition





- Disconnect harness connector -1- from Mass Air Flow sensor -2-
- Switch ON ignition
- Select 20 Volt measurement range





- Perform voltage measurement using Fluke 83 multimeter between following connector terminals:

Connector on terminal G70 Specification
3 + Ground Battery voltage (approx)
3 + 5 Battery voltage (approx)

Connector on terminal G70 Specification
1 + Ground Approx. 5 Volts
1 + 5 Approx. 5 Volts

If specifications not obtained:
- Switch OFF ignition





- Connect VAG 1598/18 Test Box to ECM harness connector
- Check wiring for open circuit between Test Box sockets and harness terminals using Wiring diagram:
terminal 1 + socket 19
terminal 2 + socket 33
terminal 3 + socket 23
terminal 5 + socket 1
terminal 6 + socket 13
Wire resistance: max. 1.5 Ohms.

- Also check wires for shorting to one another
Specification: Infinite Ohms.

If specifications obtained, check EGR Vacuum Regulator Solenoid valve N18 as follows:
- Disconnect N18 valve harness connector
- Switch Fluke 83 multimeter to resistance range





- Connect multimeter between valve terminals and measure resistance:
Specification: 14 to 18 Ohms.

If specification not obtained:
- Replace EGR Vacuum Regulator Solenoid valve N18
- Display the readiness code

If DTC memory was erased:
- Create readiness code again

If specification obtained:
- Switch ON ignition





- Connect Fluke 83 multimeter between connector terminal 1 and engine Ground using jumper wires from VW 1594 adaptor kit
Specification: approx. battery voltage.

If specification not obtained:
- Switch OFF ignition
- Check wiring for open circuit/short to positive or negative between Test Box and connector using wiring diagram:
terminal 1 + socket 68
terminal 2 + socket 25
Wire resistance: max. 1.5 Ohms.

- Also check wires for shorting to one another, to Ground and battery positive:
Specification: Infinite Ohms.

If wiring OK:
- Replace Diesel direct injection system ECM J248
- Display the readiness code

If DTC memory was erased:
- Create readiness code again