Checking lambda probe heater -Z19 for lambda probe upstream of catalytic converter — AUDI

Special tools and workshop equipment required

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

Test requirements:

Coolant temperature at least 80 °C=>Display group 004, display zone 3
Fuse for lambda probe heating OK

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

Test sequence

Unscrew protective cover -arrows- on underside of vehicle.

Unplug 6-pin connector -1- (black) for lambda probe upstream of catalytic converter -G39.

Connect up multimeter for resistance measurement between contacts 3 and 4.
Specification at ambient temperature: 2.5 ... 10 ω

If reading does not match specification:

Replace lambda probe 1 upstream of catalytic converter -G39.

If reading matches specification:

Check power supply for lambda probe heating.

Checking power supply for lambda probe heating

Connect up multimeter for voltage measurement between contacts 3 and 4.
Start engine.
Specification: approx. battery voltage

Note:

Activation and deactivation of lambda probe heating by engine control unit can be observed if necessary in function "Read measured value block", display group number 041, display zone 2.

If there is no voltage:

Connect up multimeter for voltage measurement as follows.

Connector, / contact · Measure to
3 (positive) · Vehicle earth

Briefly operate starter.
Specification: approx. battery voltage

If there is still no voltage:

Check for open circuit in wiring from contact 3 of connector via fuse to fuel pump relay.

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

If power supply is OK:

Connect up multimeter for voltage measurement as follows.

Connector, / contact · Measure to
4 (engine control unit switched earth connection) · Battery positive

Start engine.
Specification: approx. battery voltage

Note:

Activation and deactivation of lambda probe heating by engine control unit can be observed if necessary in function "Read measured value block", display group number 041, display zone 2.

Switch off ignition.

If there is no voltage:

Connect test box V.A.G 1598/31 to engine control unit wiring harness. Actual engine control unit is not to be connected=>Page
24-12
.

Check for open circuit in the following wiring.

Connector, / contact · Test box V.A.G 1598/31, / socket
4 · 5

Eliminate open circuit in wiring if necessary.

If wiring is OK, but there is no earth supply for lambda probe heating:

Replace engine control unit => Page
24-16
.