Generations

Engine Codes

Engine code	MY	Model	ECU	Notes
APB	1998-2001	North American S4	see below
ASJ	2000?	RS4	F-box
AZR	2001?-2003	RS4	Q/K-box
AGB	1997-2001?	European S4	C/D-box	No post cat O2 sensors, Bosch MAF, original intake manifold
AZB	2001?	European S4	G/N/P-box
APB	?-2002	Allroad/A6	X/L-box
BEL	2003-?	Allroad/A6	R/MX/S/T-box

MY	ECU	Build Date	MAF	BPVs	ESP	Transmission	F-hose	Notes
1997-1999	C-Box	09/97-08/99	Bosch	710	no	6-speed	yes	AGB engine code (Not available in North America), Flush door handles, Early door mirrors, Thin door trim, Analog clock in dash, No plenum chamber cover, Reversed battery terminals, Face down spare, Square side repeaters, Washer nozzles located on top of hood, Manually operated seats, Split (2-piece) Xenons with separate side repeaters
2000	A-Box	09/99-05/00		710		6-speed	yes	Possibly Al uprights, interchangable with ESP/Hitachi equipped cars but requires engine recode and a Bosch MAF
2000	B-Box	09/99-05/00		710A		Tiptronic	no	Possibly Al uprights, interchangable with ESP/Hitachi equipped cars but requires engine recode and a Bosch MAF
2001	H-Box	06/00-09/00	Hitachi	710A	yes	6-speed	yes	Steel uprights, introduction of ESP, interchangable with M-Box but requires cluster recode
2001	J-Box	06/00-09/00		710A		Tiptronic	no	Steel uprights, interchangable with L-Box
2001.5	L-Box	09/00-05/01		710B		Tiptronic		Revised TBB, updated intake manifold, sport package (w/Al mirrors) avail, Avant avail
2001.5	M-Box	09/00-05/01				6-speed, updated synchros/sliders
2002	T-Box	06/01-07/01				6-speed, updated synchros/sliders		Interchangable with M-Box
2002	AA-Box	06/01-07/01				Tiptronic		Interchangable with L-Box

Note: The build date cutoff for 2001 to 2001.5 is inconsistent and sometimes arbitrary. Both '01 and '01.5 cars have been reported as 09/00 build.
Note: Manufacturer Year is inconsistent and sometimes arbitrary. See Notes below.
Note: It is a common misconception that 2001.5 introduced updated oil lines. There is no conclusive evidence of this.

MY	Sedan	Avant	total
2000	5647	25	5672
2001	4770	1228	5998
2002	642	198	840
Total	12,096	1451	13,547

2002 is build date of 06/01 to 07/01

(MY = Model Year. CY = Calender Year)

1999MY: No '99MY Imported / Sold in the U.S.A.
2000MY: No '00MY Imported / Sold in the U.S.A.
2001MY: 1,257 Total Imported / Sold in the U.S.A. (Automatics: 404 Units. 6-Spd Manuals: 853 Units.)
2002MY: 283 Total Imported / Sold in the U.S.A. (Automatics: 188 Units. 6-Spd Manuals: 283 Units.)
2003MY: No '03MY B5/S4 Avants Sold.

Notes:

Total of 1,540 B5/S4 Avants were imported to / sold in the U.S.A.
Automatics: 592 Total Units. 6-Speed Manuals: 948 Total Units.
Audi did sell some B5/S4 Avants in 2000CY, but they were early '01MY models.
Audi is not able to differentiate between 2001MY and 2001.5 MY S4 Avants in their U.S. Market Import / Sales records.
Audi did not produce a 2003MY B5/S4 Avant. However, there were a few "left-over" 2002MY units sold in 2003CY.

Source: Audi's "Product Support Engineering" office in Auburn Hills, Michigan.

http://forums.audiworld.com/s4/msgs/802094.phtml
poll here: http://forums.audiworld.com/s4/msgs/2447926.phtml
There is some confusion with cars near the 5/00 build mark (none verified)
1. Some 2001 cars came with Bosch MAFs (and presumably A-Box ECUs).
There is some confusion with cars near the 09/00 build mark (none verified)
1. Some are 2001, some are 2001.5
2. Some 2001.5 came with H-boxes and do not appear to have F-hoses
3. Some 2001.5 are reported to have mismatching wheel/trunk badges
Andy Whittaker's UK 1999 S4 seems to have a C box as too does Nilesh "Ram" Ramrattan's MTM Stage IV car (also UK spec).
The L and AA box information may be incorrect. Please mail me or post a comment in the talk section.
If the OEM equipment on your car does not fit into this table and you are the original owner, please post a comment in the talk section.
If the OEM equipment on your car does not fit into this table and you are not the original owner, it is highly likely that some of the parts have been swapped out.