Checking air mass meter -G74 for control unit no. 8A0 906 266 B (08.92 >) — AUDI

Special tools and workshop equipment required

V.A.G 1526 A
V.A.G 1527 B
V.A.G 1594 A
V.A.G 1598 A
V.A.G 1598/11
VAS 5051 with VAS 5051/1 and VAS 5051/2

or

V.A.G 1551 with V.A.G 1551/1

Installation position => Installation position overview - Page
24-6

Checking function

Read measured value block, Display Group 001, engine at idling speed =>Page
01-114
.

Read measured value block 1
⇒
1
2
3
4
Indicated on display:

Checking display in display zone 2.
Specification: 1,470 ... 1.620 V

If the values are not as specified or if the fault memory has recorded a fault relating to the air mass meter, check the voltage supply to the air mass meter.

Checking power supply

Test requirements:

Fuse OK (in fuse holder)
▸ 06.93: S27; 07.93 ▸: S32.

Detach connector from air mass meter.

Connect voltage tester V.A.G 1527 B as follows:

Connector / contact · Measure to
3 · Engine earth

Switch the ignition on.
The LED should illuminate.

If the LED does not illuminate:

Check the wiring between contact 3 of connector and fuse for open circuit/short to earth and repair if necessary..

=> "Current Flow Diagrams, Electrical Fault Finding and Fitting Locations" binder

Note:

Use only gold-plated contacts when repairing the contacts in the plug connectors.

Checking earth supply

Pull connector off airmass meter.

Connect voltage tester V.A.G 1527 B as follows:

Connector / contact · Measure to
2 · Battery positive

The LED should illuminate.

If the LED does not illuminate:

Check wiring between contact 2 of connector and earth connection in wiring harness on right of engine compartment for open circuit and repair if necessary.

=> "Current Flow Diagrams, Electrical Fault Finding and Fitting Locations" binder

Note:

Use only gold-plated contacts when repairing the contacts in the plug connectors.

Testing signal wiring for air mass meter

With the ignition switched off, connect test box V.A.G 1598 A with adapter V.A.G 1598/11 to connector A only of engine control unit (control unit remains disconnected) => Page
24-15
.

Check for open circuit and short to positive or earth in the following wiring connections:

Connector / contact · Test box V.A.G 1598 A / socket
1 · 42

Rectify any open/short circuit as necessary.

=> "Current Flow Diagrams, Electrical Fault Finding and Fitting Locations" binder

If the wiring is OK, replace the air mass meter (G70).

Checking signal voltage

Test requirements:

Wiring OK
Air mass meter connected
Electrical consumers switched off (radiator fan must not run during the test)

Push back rubber grommet at connector of air mass meter
Connect multimeter to contacts 1 and 2 of air mass meter connector to measure the voltage.

Note:

Pin assignment is marked on back of connector.

Switch the ignition on.
Specification: 0.3 ... 1.1 V

Start engine and run at idling speed.
Increase engine speed and observe change in voltage.
Specification:
With increasing engine speed, and thus increasing air throughput, signal voltage increases proportionally up to approx. 3.4 V at 4000 rpm.

If voltage does not change, or if voltage dips with increasing engine speed:

Replace air mass meter.