1996 AUDI A4 AFC Engine On Board Diagnostic Multiport Fuel Injection Workshop Manual

X
Meaning of the 1-digit display:

Value "0" = ignition on and engine not running, or, engine running and fuel tank contents less than 12 liters (3.2 gal)
Value "1" = engine running and fuel tank contents greater than 12 liters (3.2 gal)
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Display group 028
Note:
Display group 028 is only used by Production. Display shows
Display/specified value
Designation
Basic setting 28
1 2 3 4 0 - 255 --------------------------------------
0 - 255 --------------------------------------
0 - 255 --------------------------------------
0 - 255 --------------------------------------
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01-211
Display group 029 (Diagnosis status)
Notes:
OBD II regulations require a display ("Readiness Code") that indicates readiness for inspection (annual exhaust emissions
test). The readiness code display (display field 1) shows that every component and/or system that affects the exhaust, which
can lead to switching on the MIL, has been operated at least once with positive result.
The readiness code is reset and/or erased:

Every time the DTC memory is erased (both with address word 01 function 05 and with address 33 mode 4).
When the battery is disconnected.
When the engine control module is disconnected (e.g. connecting test box VAG 1598/19, replacing ECM, etc.).
To generate the readiness code, take a "mixed city and highway" drive (short test). A "mixed city and highway" drive is
understood to be approx. 1-1/2 to 5 minutes at 80-100 km/h (50-63 mph) with manual transmission in 4th or 5th gear, or
automatic transmission selector lever in "D" position, preferably in 4th gear.
The "Trip Status" display (display field 2) shows which components and/or systems have been checked since the start of the
trip. After successful diagnosis, the current display value is set to "1" whether the diagnosis was recognized as OK or not OK.
The trip-status display is reset to "0" at each start since the components and/or systems are checked at each new start. A
"trip" is understood to be a drive of approx. 1-1/2 to 5 minutes at 80-100 km/h (50-63 mph) with manual transmission in 4th or
5th gear, or automatic transmission selector lever in "D" position, preferably in 4th gear, with preceding cold start.
The readiness code display (display field 1) shows whether the components and/or systems checked in display field 2 were
recognized as OK or not OK by the engine control module.
If the diagnosis is recognized as OK, the current display value is set to "0."
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If the diagnosis is recognized as not OK, the current display value is not set to "0", it stays at "1."
If every component and/or system has operated at least once with positive results, all display values of the readiness code
are set to "0."
If, during another diagnosis, a component and/or system is recognized as not OK, the readiness code is not reset to "1."
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01-212
If the trip status display is set to "1" when the readiness code is regenerated, but the corresponding display value of the
readiness code is not set to "0", the diagnosis was carried out but recognized as not OK by the engine control module. In this
case, the DTC memory should be checked to determine malfunctions and/or to carry out a selective diagnosis:

For three way catalytic converter diagnosis (Bank 1 and 2) also check display groups 035, 036 and 044.
For the Evaporative Emissions (EVAP) system leak diagnosis, also check display group 030.
For the Secondary Air Injection (AIR) system throughput and leak diagnosis, also check display groups 020 and 021.
For oxygen sensor diagnosis, also check display groups 032, 033, 034, 041, 042 and 043.
For oxygen sensor heating diagnosis, also check display group 040.
For the Exhaust Gas Recirculation (EGR) system throughput diagnosis, also check display group 017.
Display
shows Display specified
value Designation/diagnosis
Basic setting
29
1 2 3 4 X X X X X X 1 = Readiness Code
X X X X X X X X 2 = Trip Status display
0 - 40 3 = Counter for warm-up phases without new malfunctions except for "combustion
misfiring" and/or "oxygen sensor control"
0 - 40 4 = Counter for warm-up phases without new malfunctions except for "combustion
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misfiring" and/or "oxygen sensor control"
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01-213
Notes on display field 1:

All readiness code values are set to "1" by disconnecting the ECM harness connector and/or disconnecting the battery,
and every time DTC memory is erased (both with address word 01 function 05 and with address word 33 mode 4).
To regenerate the readiness code, take a drive of approx. 1-1/2 to 5 minutes at 80-100 km/h (50-63 mph) with manual
transmission in 4th or 5th gear, or automatic transmission selector lever in "D" position, preferably in 4th gear ("mixed city
and highway" trip).
Value "0" = Diagnosis carried out
Value "1" = Diagnosis not OK and/or diagnosis not carried out yet
X
X
X

X
X

X
Meaning of the 6-digit "readiness codes"

1 = Three way catalytic converter diagnosis (Banks 1 and 2)

2 = ----

3 = Evaporative Emissions (EVAP) throughput diagnosis

4 = Secondary air system throughput and leak diagnosis (Always "0" for vehicles without
secondary air injection system)

5 = ----

6 = Heated oxygen sensor diagnosis (flank rise and/or flank fall time of the voltage signal of
heated oxygen sensors in front of three way catalytic converters

7 = Oxygen sensor heating diagnosis (all four O2S heaters)

8 = Exhaust Gas Recirculation (EGR) throughput diagnosis
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Notes on display field 2:

The display values are set to "0" at each start, since the function capability of components and systems that can affect the
exhaust are checked again and again.
Leak testing of the EGR system is only carried out after a preceding cold start (water temperature -10 C to 30 C (14 to
86 F). Value "0" = Diagnosis not carried out yet
Value "1" = Diagnosis carried out
X
X
X
X
X
X
X
X
Meaning of 8-digit "Trip Status" display

1 = Three way catalytic converter diagnosis, banks 1 and 2
(for diagnostic conditions display group 044)
2 = Exhaust Gas Recirculation (EGR) system leak testing

3 = Evaporative Emissions (EVAP) throughput diagnosis
(for diagnostic conditions display group 030)
4 = Secondary air injection system throughput and leak testing
(always "0" on vehicles without secondary air injection system; for diagnostic conditions
display groups 020 and 021)
5 = Oxygen sensor control diagnosis
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