Exhaust Gas Recirculation and MAF Sensor Function, Checking
NOTE: The Mass Air Flow signal is required for the ECM to calculate the optimum amount of fuel to inject and the degree of EGR control to administer. The smaller the Mass Air Flow signa4 the smaller the quantity of fuel injected.
Special tools, testers, measuring instruments and auxiliary items required
- VAG 1551/1552 Scan Tool using VAG 1551/3 adaptor cable
- VAG 1598/22 Test Box
- Fluke 83 multimeter
- VW 1594 Adaptor kit
- Wiring diagram
Test sequence
- Connect VAG 1551/1552 Scan Tool. Testing and Inspection
- Start engine and let idle
- Press 0 and 1 buttons to select Address word 01: "Engine electronics"
WARNING! Secure Scan Tool to rear seat and operate from this position using a second technician.
Display will appear as shown
Rapid data transfer HELP
Select function XX
- 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, 1 and 0 buttons to select "Display group 10"
- Press Q button to enter input
- Observe display in display zone 1.
- Specification: 240 to 340 mg/H
Read measuring value block 10 ->
309 mg/h 1027 mber 1011 mbar 0.0%
If specification not obtained
- Check Exhaust Gas Recirculation.
If specification obtained
- Accelerate vehicle in 3rd gear from about 1500 rpm under Wide Open Throttle.
- Press PRINT button on VAG 1551 at approx. 3000 rpm.
- Specified value in display field 4:100 %
Read measuring value block 10 ->
830 mg/h 1027 mbar 1850 mbar 100%
If specification not obtained
- Repeat test and accelerate vehicle under Wide Open Throttle
- Specified value in display field 1:800 mg/H minimum
(intake air mass)
Read measuring value block 10 ->
830 mg/h 1027 mbar 1850 mbar 100%
If specification not obtained
- Replace Mass Air Flow sensor.
- Display Readiness code. Testing and Inspection
If DTC memory has been erased
- Create Readiness code. Testing and Inspection
If display field 1 shows constant 550 mg/H (firm replacement value):
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End transfer"
- Press Q button to enter input
- Switch OFF ignition.
- Disconnect Mass Air Flow sensor harness connector. Service and Repair
- Switch ON ignition.
- Measure Mass Air Flow sensor voltage supply between the following connector terminals:
G70 connector terminal Specification
2 + Ground Approx. battery voltage
2 + 3 Approx. battery voltage
4 + Ground Approx. 5 Volts
4 + 3 Approx. 5 Volts
If specifications not obtained
- Switch OFF ignition.
- Connect VAG 1598/22 Test Box to ECM wiring harness.
- Check wiring for open circuit between Test Box and harness connector using Wiring diagram.
- Terminal 2 + socket 2 and 28
- Terminal 3 + socket 4
- Terminal 4 + socket 50
- Terminal 5 + socket 52
- Wire resistance: 1.5 Ohms maximum
- Check wires for short to one another, to vehicle Ground and to battery Plus.
- Specification: Infinity Ohms
If wiring OK
- Replace Diesel Direct Injection system ECM J248.
- Display Readiness code. Testing and Inspection
If DTC memory has been erased
- Create Readiness code. Testing and Inspection