Checking lambda probe 1 heater after catalytic converter Z29 — AUDI

Checking
lambda probe 1 heater after catalytic converter
Z29
Special tools and workshop equipment required
Portable 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
121-pin adapter cable
V.A.G 1598/31
(test box)
Conditions
Coolant temperature at least 80 °C
Fuse for lambda probe heating OK
Current flow diagrams, Electrical fault finding and Fitting locations
Test sequence
Unscrew protective cover
2
arrows
.
Unplug 4-pin connector (brown) to
lambda probe after catalytic converter
G130
.
Connect up multimeter (resistance measuring range) between contacts
1
and
2
.
Specification at ambient temperature: 6,4 … 47,5 Ω.
If reading does not match specification:
Replace lambda probe downstream of catalytic converter.
If reading matches specification:
Check power supply of lambda probe heating.
Checking power supply of lambda probe heating
Connect up 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:
Connect up multimeter (voltage measuring range) between contact
1
(positive) and vehicle earth.
Briefly operate starter.
Specification: approx. battery voltage
If there is still no voltage:
Use current flow diagram to check wiring from contact
1
of connector via fuse to fuel pump relay for open circuit.
If power supply is OK:
Connect up multimeter (voltage measuring range) between contact
2
(engine control unit switched earth connection) 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:
Connect
121-pin adapter cable
V.A.G 1598/31
(test box) to wiring harness to engine control unit, but do not connect actual engine control unit
Chapter
.
Check for open circuit in the following wiring:
Connector
Contact
121-pin adapter cable
V.A.G 1598/31
Socket
2
63
Repair wiring if necessary.
If the wiring is OK but there is no switched earth connection for the lambda probe heating:
Replace engine control unit
Chapter
“
Removing and installing engine control unit without protective housing
”
or
Chapter
“
Removing and installing engine control unit with protective housing
”
.