Checking Lambda probe heating Z19 for Lambda probe before catalytic converter — AUDI

Checking
Lambda probe heating
Z19
for Lambda probe before catalytic converter
Special tools and workshop equipment required
Hand-held multimeter
V.A.G 1526 A
or
V.A.G 1526 B
Adapter set
V.A.G 1594 A
or
V.A.G 1594 C
Adapter cable, 121-pin
V.A.G 1598/31
(test box)
Procedure
Coolant temperature at least 80 °C.
Fuse for Lambda probe heating OK
Current flow diagrams, Electrical fault finding and Fitting locations
.
Unbolt the protective cover
arrows
.
Unplug 6-pin connector (black) to
Lambda probe
G39
(before catalytic converter).
Connect multimeter (resistance test range) between contacts
3
and
4
.
Specification: 2.5 ... 10 Ω (at room temperature).
If specification is not obtained:
Renew Lambda probe before catalytic converter.
If the specification is obtained:
Check voltage supply for Lambda probe heating.
Checking voltage supply
Connect multimeter (voltage test 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 in display zone 2 of
“measured value block 041”
.
If there is no voltage reading:
Connect multimeter (voltage measuring range) between contact
3
(positive) and earth.
Operate the starter briefly.
Specification: approx. battery voltage
If there is still no voltage reading:
Refer to current flow diagram to check for open circuit in wiring from contact
3
of connector via fuse to fuel pump relay.
If the voltage supply is OK:
Connect multimeter (voltage measuring range) between contact
4
(switched earth connection from engine control unit) and 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 in display zone 2 of
“measured value block 041”
.
Switch off ignition.
If there is no voltage reading:
Connect
adapter cable, 121-pin
V.A.G 1598/31
(test box) to wiring harness for engine control unit, but do not connect the engine control unit itself
Chapter
.
Check for open circuit in the following wiring connection:
Connector
Contact
Adapter cable, 121-pin
V.A.G 1598/31
Socket
4
5
Repair wiring connection if necessary.
If the wiring is OK but there is no switched earth connection for the Lambda probe heating:
Renew engine control unit
Chapter
“
Removing and installing engine control unit without protective housing
”
or
Chapter
“
Removing and installing engine control unit with protective housing
”
.