Checking lambda probe and lambda regulation after catalytic converter — AUDI

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
Test box V.A.G 1598/31
Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Adapter set V.A.G 1594
Current flow diagram

Check conditions

Coolant temperature must be at least 80 °C, =>display group 04, display zone 3.
Exhaust system between catalytic converter and cylinder head must be free of leaks

Functional check

Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit. When doing this the engine must be running at idling speed.
(Connecting fault reader and selecting engine control unit
=> Page
01-13
.)

Rapid data transfer
HELP
Select function XX
Indicated on display:

Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

Read measured value block
HELP
Input display group number XXX
Indicated on display:

Press keys 0, 3 and 0 for the "Display group number 30" and confirm entry with Q key.

Read measured value block
30
⇒
1
2
3
4
Indicated on display:
(1...4 = Display zones)

Check lambda regulation status before catalytic converter (display zone 2):
Specification: 1 1 0

Note:

The 3rd bit in display zone 2 (lambda regulation active) will not be set to 1 until the engine is run under part throttle conditions (2500-4000 rpm).

Significance of 3 digit number block in display zone 1:

Significance if display = 1
1 · 2 · 3
x · Lambda regulation active (specification: 1/0)
1 · Lambda probe operationally ready
1 · Lambda probe heating on

Notes:

The lambda control of lambda probe (after the catalytic converter; B1-P2) is not active when the engine is not running under load.
The first digit of the three-digit display (heating) fluctuates between 0 and 1.

If the specification is not obtained:

Check lambda probe heating after catalytic converter
=> Page
24-31
.
Check basic voltage => Page
24-112
.

If the specification is obtained:

Press ⇒key.
Press keys 0 and 4 for the function "Initiating basic settings" and confirm entry with Q key.

Basic setting
HELP
Input display group number XXX
Indicated on display:

Press keys 0, 3 and 6 for "Display group number 36" and confirm entry with Q key.

System in basic setting
36
⇒
1
2
3
4
Indicated on display:
(1...4 = Display zones)

Apply brake and hold down brake pedal. The engine speed will be raised automatically. After a moment, the following appears in display zone 2:
B1-P2 OK

If "B1-P2 n.OK"
appears in display zone 2,

Check lambda probe 2 voltage at idling speed in display zone 1.
Specification: 0.000...1.000 V
Continue check according to following table.

Display · Cause · Continuation of check
Between 0.400... / 0.500 V · Open circuit · => Page checking lambda probe wiring 24-113
1.105 V · Short to positive
0.000 V · Short to earth

If the lambda regulation in display zone 1 does not fluctuate as stated:

Press ⇒key.
Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
Carry out road test and burn lambda probes clean and repeat check.

Observe the valid safety precautions when carrying out a road test => Page
24-27
.

If the the specifications in display zone 1 are not obtained even after a test drive, or the value does not fluctuate by at least 2 %:

Check basic voltage => Page
24-112
.

Checking basic voltage

Unplug 4-pin connector for lambda probe (G130) -2-.

Connect multimeter with aux. cables from V.A.G 1594 to measure voltage at contacts 3+4 (connector to engine control unit).
Switch on ignition and measure basic voltage.
Specification: 0.40...0.50 V
Switch off ignition.

If the specification is obtained:

Renew the lambda probe after catalytic converter (G130).

Checking lambda probe wiring, lambda probe 2

Unplug 4-pin connector for lambda probe (G130) -2-.

Check wiring for open circuit between test box and 4-pin connector (to control unit) using current flow diagram.
Contact 3+socket 68
Contact 4+socket 69
Wire resistance: Max. 1.5 ω
Check the wiring at connector contacts 3+4 for short circuit to contacts 1+2.

If no fault is detected in the wiring:

Renew the lambda probe after catalytic converter (G130).