Checking Lambda probe heating Z29 for Lambda probe after catalytic converter — AUDI

Checking
Lambda probe heating
Z29
for Lambda probe after 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 4-pin connector (brown) for
Lambda probe after catalytic converter
G130
.
Connect multimeter (resistance measurement range) between contacts
1
and
2
.
Specification: 6.4 ... 47.5 Ω (at room temperature).
If specification is not obtained:
Renew Lambda probe after catalytic converter.
If the specification is obtained:
Check voltage supply for Lambda probe heating.
Checking voltage supply for Lambda probe heating
Connect multimeter (voltage measuring range) between contacts
1
(positive) and
2
(earth).
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 4 of
“measured value block 041”
.
If there is no voltage reading:
Connect multimeter (voltage measuring range) between contact
1
(positive) and vehicle 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
1
of connector via fuse to fuel pump relay.
If the voltage supply is OK:
Connect multimeter (voltage measuring range) between contact
2
(switched earth connection from engine control unit) and battery positive.
Start engine.
Specification: approx. battery voltage (may fluctuate).
Note
The point at which the engine control unit switches the Lambda probe heating on and off can be observed in display zone 4 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
2
63
Repair wiring connection if necessary.
If the wiring connection is O.K. but the Lambda probe heating has no switched earth connection:
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
”
.