0 - Automatic
1 - SAE J1850 PWM (41.6 kbaud)
2 - SAE J1850 VPW (10.4 kbaud)
3 - ISO 9141-2 (5 baud init, 10.4 kbaud)
4 - ISO 14230-4 KWP (5 baud init, 10.4 kbaud)
5 - ISO 14230-4 KWP (fast init, 10.4 kbaud)
6 - ISO 15765-4 CAN (11 bit ID, 500 kbaud)
7 - ISO 15765-4 CAN (29 bit ID, 500 kbaud)
8 - ISO 15765-4 CAN (11 bit ID, 250 kbaud)
9 - ISO 15765-4 CAN (29 bit ID, 250 kbaud)
A - SAE J1939 CAN (29 bit ID, 250* kbaud)
B - USER1 CAN (11* bit ID, 125* kbaud)
C - USER2 CAN (11* bit ID, 50* kbaud)

There are several CAN physical layer standards:
    ISO 11898-1: CAN Data Link Layer and Physical Signalling
    ISO 11898-2: CAN High-Speed Medium Access Unit
    ISO 11898-3: CAN Low-Speed, Fault-Tolerant, Medium-Dependent Interface
    ISO 11898-4: CAN Time-Triggered Communication
    ISO 11898-5: CAN High-Speed Medium Access Unit with Low-Power Mode
    ISO 11898-6: CAN High-speed medium access unit with selective wake-up functionality
    ISO 11992-1: CAN fault-tolerant for truck/trailer communication
    ISO 11783-2: 250 kbit/s, Agricultural Standard
    SAE J1939-11: 250 kbit/s, Shielded Twisted Pair (STP)
    SAE J1939-15: 250 kbit/s, Unshielded Twisted Pair (UTP) (reduced layer)
    SAE J2411: Single-wire CAN (SWC)

For initial tests, I used a Debian or Ubuntu laptop with the minicom program to capture output from the Bluetooth-paired OBDLink MX scantool, which Linux offers as /dev/rfcomm0, a regular soft tty. (On Ubuntu 10.10, bluetooth-agent failed to handle random password, while blueman-assistant worked on the first try.) nOBDy's genericbod2 provider plugin will log data from the OBDLink MX with no problem, but, at the moment, the underlying libobd communication library only supports the OBDII (15765-4) protocol. The OBDLink MX is a bit expensive compared to many scantools, but most don't populate pins 3 and 11 or read MS-CAN communications (see below).

1. Auto-protocol for OBDII on pins 5, 6 and 14
   At minicom, I type: "ATSP0;ATDPN"
   Vehicle responds: "A6 [AT]"
   I type: "ATSP0;STRPRS"
   Vehicle responds: "AUTO, ISO 15765-4 (CAN 11/500) [AT]"
   
2. HS CAN (ISO 11898, 11-bit Tx, 500kbps, var DLC) on pins 3, 11 and 5 (?)
   I type: "STP31; STPRS"
   Vehicle responds: "HS CAN (ISO 11898, 500K/11B)"
   
3. MS CAN (ISO 11898, 11-bit Tx, 125kbps, var DLC) on pins 3, 11 and 5 (?)
   I type: "STP51;STPRS":
   Vehicle responds: "MS CAN (ISO 11898, 125K/11B)"
   

Sample Log file from Mazda 3 raw CAN monitoring session

Compare HS-CAN and MS-CAN data from madox.net. A quick comparison shows that a lot of the same IDs appear in my MS-CAN (protocol 51) data stream (201, 265, 401, 433) and HS-CAN (protocol 31) data stream (200, 20F, 231, 433, 4B0) although it's not obvious that the behavior matches that of madox's 2006 Mazda 3. For example, in my vehicle, 20F PID appears to be a monotonically increasing counter in least-signicant byte, while madox identifies bytes 2 and 3 as speed. Pinning down an interpretation of many of the parameters is clearly possible but will require investment of some time.

080-11 DRIVE MODE[LF, L3]

- Using the OBD-II drive mode, the monitoring item requested by OBD-II
regulations can be easily diagnosed.
- Performing the Drive Mode inspects the OBD-II system for proper
operation and must be performed to ensure that no additional DTCs are
present.
- The OBD-II drive mode is divided into the specific drive mode and single drive mode.
- For the specific drive mode, specified drive modes have been set for
each individual monitoring item requested by OBD-II regulations, and
they can be diagnosed individually. For the single drive mode, the
entire monitoring item requested by OBD-II regulations can be diagnosed.
- The following modes are in the specific drive mode. The applicable
system is diagnosed by driVing in the following drive modes.

  PCM (Powertrain Control Module): Adaptive Memory Produce Drive Mode
  EGR (Exhaust Gas Recirculation): System Repair Verification Drive Mode
  H02S heater, H02S, and TWC Repair: Verification Drive Mode
  EVAP System Repair: Verification Drive Mode

- The following systems are diagnosed with the single drive mode.

  EGR system
  Oxygen sensor (H02S)
  Oxygen sensor heater
  Catalytic converter (TWC)
  Fuel, misfire and evaporative (EVAP) system


PCM Adaptive Memory Production Drive Mode
1.	 Start the engine and warm it up completely.
2.	 Verify the following conditions and correct if necessary:
- All accessory loads (AlC, headlights, blower fan, rear window defroster) are off.
3.  Perform no load racing at the engine speed shown in the graph,
then idle the engine for more than 60 s after the cooling fan has
stopped. If possible, monitor RPM PID for engine speed during this
procedure.

p. 63-71, shop manual, 9-page table including and associated fault conditions.

DIAGNOSTIC MONITORING TEST RESULTS[LF, L3]
The purpose of this test mode is to confirm the result of OBD-II
monitor diagnostic test results. The result values stored when
particular monitor is completed are displayed. If the monitor is not
completed, initial value is displayed.

p. 2128:

ON-BOARD DIAGNOSTIC [ELECTRO HYDRAULIC POWER ASSIST STEERING (EHPAS)]
B1238 EHPAS control module
B1317 Battery power supply
B1318 Battery power supply
B1342 EHPAS control module
B1352 Ignition power supply
B2477 EHPAS control module configuration
C1099 Electric power steering oil pump (motor)
C1278 Steering angle sensor
U0073 CAN bus communication error
U0100 Lost communication with the PCM
U2023 EHPAS control module
B1317 DTC Fault received from other modules

p. 2129

PID Name (Definition)
MTR_AMP(Pump Motor Operation Current)
RPM_ACT (Actual pump motor revolution per minutes)
RPM_TGT (Target pump motor revolution per minutes)
ENGRPM (Engine speed signal)
STEER_RATE (Steering wheel rotation rate)
TEMP_BOARD (Printed circuit board temperature)
VPWR (Module supply voltage)
VSS (Vehicle speed)