Checking Lambda probe heater Z19 for Lambda probe G39 — AUDI

Checking
Lambda probe heater
Z19
for
Lambda probe
G39
Special tools and workshop equipment required
V.A.G 1526 A
V.A.G 1594 A
V.A.G 1598/31
Test sequence
Note
Coolant temperature at least 80 °C
Fuse for Lambda probe heating OK
Current flow diagrams, Electrical fault finding and Fitting locations
Unscrew the protective cover
arrows
.
Unplug the 6-pin connector (black) to the
Lambda probe
G39
.
Connect up the multimeter (resistance measuring range) between contacts 3 and 4.
Specification: 2.5 ... 10 Ω (at room temperature)
If the reading does not match the specification:
Replace the
Lambda probe
G39
.
If the reading matches the specification:
Check voltage supply for Lambda probe heating.
Checking voltage supply for
Lambda probe heater
Z19
Connect up the multimeter (voltage measuring range) between contacts 3 and 4.
Start engine.
Specification: approx. battery voltage
Note
The point at which the engine control unit switches the Lambda probe heating on and off can be observed if applicable in the
“Reading measured value block”
function, display group number 041, display zone 2.
If there is no voltage:
Connect up the multimeter (voltage measuring range) as follows.
Connector
Contact
Measure to
3 (positive)
Vehicle earth
Briefly operate the starter.
Specification: approx. battery voltage
If there is still no voltage:
Check for open circuit in the wiring from contact 3 of the connector via the fuse to the fuel pump relay:
If the voltage supply is OK:
Connect up the multimeter (voltage measuring range) as follows:
Connector
Contact
Measure to
4 (engine control unit switched earth connection)
Battery positive
Start engine.
Specification: approx. battery voltage
Note
The point at which the engine control unit switches the Lambda probe heating on and off can be observed if applicable in the
“Reading measured value block”
function, display group number 041, display zone 2.
Switch off ignition.
If there is no voltage:
Connect the test box
V.A.G 1598/31
to the wiring harness to the engine control unit, but do not connect the actual engine control unit
Chapter
.
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.
Current flow diagrams, Electrical fault finding and Fitting locations
If the wiring is OK but there is no earth supply for the Lambda probe heating:
Replace the engine control unit
Chapter
.