Checking lambda probe heating for lambda probes upstream or downstream of catalytic converter — AUDI

AMM AMX ASM BDV
Special tools and workshop equipment required

V.A.G 1526 A
V.A.G 1594 A
V.A.G 1598/31
V.A.G 1788/10
VAS 5051 with VAS 5051/1

or

V.A.G 1551 with V.A.G 1551/3 A

Note:

The lambda probe heating circuit is monitored by the self-diagnosis system.

Interrogate fault memory=> Page
01-9
.

Connect vehicle diagnostic, testing and information system VAS 5051 or fault reader V.A.G 1551 and select engine electronics control unit with "Address word" 01 => Page
01-3
For this purpose, the engine must be running at idle speed.

Rapid data transfer
HELP
Select function XX
Indicated on display

Enter "08" to select the function "Reading measured value block" and confirm entry with Q key.

Reading measured value block
Q
Enter display group number XXX
Indicated on display

Enter "041" for "display group number 041" and confirm entry with Q key.

Read measured value block
41
⇒
1
2
3
4
Indicated on display

Check specifications in display zones 1 and 3:

Note:

By increasing the engine speed the achieving of the specified values can be accelerated.

Display zones
1 · 2 · 3 · 4
Display group 041: Lambda probe heating (bank 1) at idling speed
Display · xxx kOhm · --- · xxx kOhm · ---
Display · Bank 1, probe 1 · Status of heating · Bank 1, probe 2 · Status of heating
Range · Htg. u.c.c. ON / Htg. u.c.c. OFF · Htg. d.c.c. ON / Htg. d.c.c. OFF
Specified value · 0...0.9 kOhm · Htg.u.c.c. ON/OFF · 0...0.9 kOhm · Htg. d.c.c. ON/OFF

Important notes on display zones 1, 2, 3 and 4:

If the lambda probes have not reached their operating temperature there is no display in display zones 1 and 3, i.e. both zones are empty. (Increase engine speed to achieve specified values.)
After reaching the operating temperature of both lambda probes a resistance of lower than 0.9 Ohm must be shown in display zones 1 and 3.
Only carry on with test when a resistance value lower than 0.9 kOhm is shown in display zones 1 and 3.
In certain operating points, the engine control unit "cycles" for the lambda probe heating. This means that at these points the lambda probe heating is continuously switched on and off. It is also possible that "Htg. u.c.c. OFF" or "Htg. d.c.c. OFF" is displayed as specified value in display zones 2 and 4.

Press Ckey.

Reading measured value block
Q
Enter display group number XXX
Indicated on display

Enter "042" for "display group number 042" and confirm entry with Q key.

Read measured value block
42
⇒
1
2
3
4
Indicated on display

Check specifications in display zones 1 and 3:

Display zones
1 · 2 · 3 · 4
Display group 042: Lambda probe heating (bank 2) at idling speed
Display · xxx kOhm · --- · xxx kOhm · ---
Display · Bank 1, probe 2 · Status of heating · Bank 2, probe 2 · Status of heating
Range · Htg. u.c.c. ON / Htg. u.c.c. OFF · Htg. d.c.c. ON / Htg. d.c.c. OFF
Specified value · 0...0.9 kOhm · Htg. u.c.c. ON/OFF · 0...0.9 kOhm · Htg. d.c.c. ON/OFF

Important notes on display zones 1, 2, 3 and 4:

If the lambda probes have not reached their operating temperature there is no display in display zones 1 and 3, i.e. both zones are empty. (Increase engine speed to achieve specified values.)
After reaching the operating temperature of both lambda probes a resistance of lower than 0.9 Ohm must be shown in display zones 1 and 3.
Only carry on with test when a resistance value lower than 0.9 kOhm is shown in display zones 1 and 3.
In certain operating points, the engine control unit "cycles" for the lambda probe heating. This means that at these points the lambda probe heating is continuously switched on and off. It is also possible that "Htg. u.c.c. OFF" or "Htg. d.c.c. OFF" is displayed as specified value in display zones 2 and 4.

If specified value is not attained:

Check the voltage supply to the lambda probe heating =>Page
24-138
.
Check lambda probe signal line and actuation => Page
24-131
.

Checking voltage supply for lambda probe heating

Fitting location of connectors => Fitting locations overview Page
24-5

Test requirements:

Fuse for lambda probe heating OK.

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

Fuel pump relay OK; checking =>Page
24-65
.

Disconnect 4- pin connector to relevant Lambda probe.

Connect multimeter between contacts 1 and 2 to measure voltage.

Start the engine.
Specified value: approx. battery voltage, may fluctuate

Notes:

At certain operating points, the engine control unit "cycles" the earth for the lambda probe heating. This means that at these points, the earth is continuously switched on and off. For this reason, the voltage reading on the tester may fluctuate.
Points at which Lambda probe heating is switched on and off by engine control unit can be observed in "Reading measured value block" function, display group number 041 and 042.

If no voltage is present:

Connect multimeter as follows to measure voltage:

Connector / Contact · Measure at
1 (positive) · Vehicle earth

Operate starter briefly.
Specified value: approx. battery voltage

If again no voltage is present:

Check the wiring from contact 1 on the connector via the fuse to the fuel pump relay for an open circuit.

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

If voltage supply is OK:

Connect multimeter as follows to measure voltage:

Connector / Contact · Measure at
2 (earth actuation by engine control unit) · Battery positive

Start the engine.
Specified value: approx. battery voltage, may fluctuate

Switch ignition off.

If no voltage is present:

Connect test box V.A.G 1598/31 to wiring harness for engine control unit; do not connect the engine control unit => Page
24-17
.

Check for open circuit in the following wiring connections:

Lambda probe heating -Z19 Bank 1 upstream of catalytic converter:

Connector / Contact · Test box V.A.G 1598/31 / Socket
2 · 5

Lambda probe heating -Z28 Bank 2 upstream of catalytic converter:

Connector / Contact · Test box V.A.G 1598/31 / Socket
2 · 4

Lambda probe heating -Z29 Bank 1 downstream of catalytic converter:

Connector / Contact · Test box V.A.G 1598/31 / Socket
2 · 63

Lambda probe heating -Z30 Bank 2 downstream of catalytic converter:

Connector / Contact · Test box V.A.G 1598/31 / Socket
2 · 6

If no wiring fault is detected:

Replace appropriate lambda probe.
Read out readiness code =>Page
01-74
.