Testing lambda probe heating -Z19 at lambda probe (before catalytic converter) — AUDI

ARG AVV
Special tools and workshop equipment required

V.A.G 1526 A
V.A.G 1594 A
V.A.G 1598/31

Requirements for test:

Coolant temperature at least 80 °C

Fuse for lambda probe heating OK

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

Test sequence

Unplug 6-pin connector (black) for lambda probe (before catalytic converter) -G39.

Note:

For access to connector, unscrew bolts securing coolant expansion tank and pivot expansion tank clear to the side. The coolant hoses do not have to be disconnected.

Connect multimeter (resistance measurement range) between contacts 3 and 4.
Specification: 2.5 ... 10 ω(at room temperature)

If the specification is not attained:

Replace the lambda probe 1 (before catalytic converter) -G39.

If the specification is obtained:

Test voltage supply for lambda probe heating.

Testing voltage supply for lambda probe heating

Connect multimeter (voltage measurement range) between contacts 3 and 4.
Start the engine.
Specification: approx. battery voltage

Note:

If required, observe Display Group 041, display zone 2 in the "Read measured value block" function to find out when the engine control unit is switching the lambda probe heating on and off.

If no voltage is present:

Connect multimeter (voltage measurement range) as follows:

Connector / Contact · Measure against
3 (positive) · Vehicle earth

Operate starter briefly.
Specification: approx. battery voltage

If there is still no voltage reading:

Test for open circuit in wiring connection between fuel pump relay and contact 3 on connector via fuse:

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

If the voltage supply is OK:

Connect multimeter (voltage measurement range) as follows:

Connector / Contact · Measure against
4 (switched earth connection from engine control unit) · Battery positive

Start the engine.
Specification: approx. battery voltage

Note:

If required, observe Display Group 041, display zone 2 in the "Read measured value block" function to find out when the engine control unit is switching the lambda probe heating on and off.

Switch off ignition.

If no voltage is present:

Connect test box V.A.G 1598/31 to wiring harness for engine control unit. Do not connect to the engine control unit itself.
=> Page
24-10
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Test for open circuits in the following wiring connection:

Connector / Contact · Test box V.A.G 1598/31 / Socket
4 · 5

Rectify any open circuits.

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

If the wiring connection is O.K. but the lambda probe heating still has no earth connection:

Fit a new engine control unit => Page
24-13
.