That’s a very interesting question. There are two ways to answer this.
The easiest way is that any OBD2 reader can read the “P” codes on these cars, but you won’t get the codes for the Transmission and ABS.
Other than the formidable, and rare, PDU which can do everything, there’s the WDS, which can do everything BUT resetting the base idle adaptations.
After that, there’s the Genrad 500 or 510 handheld code reader, which can monitor points, as well as pull all of the codes. Unlike the WDS and PDU, it cannot reset a TPS, reorient oxygen sensors, etc. It is strictly a code reader and point monitor, which I think is what you’re looking for. It is also rare, but they do pop up from time to time.
After that, it get’s pricey. I am not sure whether the AUTEL or FOXWELL units read ABS and Transmission codes from our older cars. I’m sure if you do a forum search, you can find some owners, but will they be owners of the AJ16 engines?
Here is a list I’ve pulled from anther site. Hopefully this helps:
•AutoEnginuity, tested on 2003 XK8, 2000 XJ8, 2011 XJ, 2004 STR amd 2007 XKR (enhanced sensor/function availability, for an additional charge (issues with 1996 and older)
•TOPTQK, tested on 2000 XKR and 2003 S-typeR
•Innova 2030, tested on 2001 XK8 and 2004 XJ8
•Innova 3030, tested on 2001 S-Type, 2008 XKR and 1996 XJR6
•Innova 3100, tested on 2002 XK8 (My 3 year old INNOVA 3100 says ‘CAN compatible’ on the face, has the color coded LEDs and PC link reports)
•Innova 3100f, tested on 2006 XK8
•Innova 3120, tested on 1995 XJ12
•Innova 3130, tested on 2000 XJ8
•CodeKey, tested on 1995 XJ6, 1999 XK8
•Actron CP9035, tested on 2003 X-type
•Actron CP9175, tested on 2001 S-Type and 1996 XJR6
•Actron CP9180, tested on 2004 S-type
•Actron CP9185, tested on 2002 XKR
•Actron CP9575, tested on 1999 XJR
•Actron CP9580A, tested on 2004 XJR
•BAFX BAFX in conjunction with Torque for Android, tested on 2006 XKR
•OBDkey, tested on 2001 S-type and X350 XJR
•OBDCOM, tested on 1998 XJR, 2000 XK8, 2001 S-Type, 2003 S-type, 2005 S-Type R and 2009 XF
•CEN-TECH 94169, tested on 2007 XJ8
•CEN-TECH 98614-2VGA Scanner, tested on 2000 XK8 with real time data logging
•CanOBD2 3030, tested on 2002 X-type
•carcode.com software based and cable unit, tested on 2001 XKR and 2003 S-type
•Craftsman 87702 (Innova 3100g), tested on 2005 XK8 and XJ8
•ELM327 bluetooth or hardwired version, with Torque app (for Android), tested on 1998 XJR, 2003 XJ8 and 2005 XJ8,
•Kiwi PLX bluetooth, with Torque app (for Android), tested on 2003 S-Type R
•Memoscan U480, tested on 1999 XJR and 2006 S-type
•ProScan under www.myscantool.com, tested successfully on 1996 XJR6, 2003 XJ8, and 2001 S-Type