Checking Lambda probe and Lambda regulation: VW 1.6 (AEH, AKL)

AKL
Note:

Only gold-plated contacts may be used when servicing Lambda probe connector contacts 3 and 4.

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

Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Fault reader V.A.G 1551 (or vehicle system tester V.A.G 1552) with cable V.A.G 1551/3
Adapter set V.A.G 1594
Test box V.A.G 1598/22

Current flow diagram

Check conditions

The fuses 1, 31 and 36 must be OK.
The battery voltage must be at least 11.5 V.
Earth connection in plenum chamber OK.

Exhaust system between catalyst and cylinder head must be free of leaks
All electrical consumers, e.g. lights and rear window heating must be switched off.
If the vehicle is equipped with an air conditioner, this must be switched off.
On vehicles with an automatic gearbox the selector lever must be in P or N.
No faults must be stored in fault memory => Page
01-17
, interrogating and erasing fault memory.
Coolant temperature must be at least 80 °C, =>Display group 01, display zone 2.

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
01-5
.)

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
Input display group number XXX
Indicated on display:

Press keys 0, 0 and 1 for "Display group number 1" and confirm entry with Q key.

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

Check whether the coolant temperature is above 80 °C in display zone 2.
Change to display group 20 as follows:
Press C key.

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

Press keys 0, 2 and 0 for "Display group number 20" and confirm entry with Q key.

Read measured value block 20
⇒
1
2
3
4
Indicated on display:
(1...4 = Display zones)

Checking Lambda control operating condition in display zone 4:

Lambda control operating condition display:

No fault in fault memory:

1st position from left must display 0
Display: 0xxxxxxx

Lambda regulation not at limit:

5th position from left must display 0
Display: xxxx0xxx

Lambda regulationactive:

6th position from left must display 1
Display: xxxxx1xx

Lambda probe operationally ready:

7th position from left must display 1
Display: 00000010

Condition of mixture:

8th position from left must display 0 and 1 alternately.
Display: xxxxxxx0 = lean mixture
Display: xxxxxxx1 = rich mixture

Observe notes concerning figures in 8-digit number block => Page
01-90
.

Note:

The other positions can show 1 or 0.

Press C key.
Press keys 0, 0 and 1 for "Display group number 1" and confirm entry with Q key.

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

Check Lambda probe voltage in display zone 3.
The voltage must fluctuate
at least 30 times per minute
in the range of
0.00...1.00 V.
Press ⇒key.
Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
Switch off ignition.
Perform check according to following table:

Appears on display · Possible fault cause · Fault elimination
Fluctuates at least 30 times per minute in range of 0.00...1.00 V · - Lambda probe and Lambda regulation OK · ---
Constant approx. 5.00 V · - Short to positive via: / - Lambda probe, probe wiring, earth wiring, engine control unit · - Check Lambda probe wiring / => Page 24-97
Constant between / 1.50...1.60 V · - Wiring open circuit via: / - Fuse, Lambda probe, probe wire, earth wire, engine control unit
Constant about 0.00 V · - Short to earth via: / - Lambda probe, probe wire, earth wire, engine control unit

If the specifications for Lambda control operating conditions are not attained or the probe voltage does not fluctuate as stated:

Check Lambda probe heating => Page
24-28
.
Check Lambda probe for soot. Renew if necessary=> Page
24-13
, item
25
.

Checking Lambda probe wiring

Connect test box V.A.G 1598/22 to control unit wiring harness.

Separate 4-pin connector (brown) to Lambda probe (G39) -arrow-.

Check wiring for open circuit between test box and 4-pin connector using current flow diagram.
Contact 3 and test box connector 25
Contact 4 and test box connector 26
Wire resistance: max. 1.5 ω
Additionally check wiring at 4-pin connector for short to one another.
Specification: ∞ω

If no wiring fault is detected:

Renew Lambda probe (G39)
=>Page
24-13
, item
25
.
Interrogate fault memory, if necessary, repair any faults and then erase fault memory => Page
01-17
, interrogating and erasing fault memory.