Posted on Leave a comment

Bargain Bin USB-ODB Interface

ODB Adaptor
ODB Adaptor

This is a little bit of kit I got to talk to the Webasto TT-V I salvaged from a scrap Jaguar S-Type, and converts USB-RS232 to the standard car diagnostic ODB connector. (These are a much cheaper option at £4 than the official Webasto diagnostic adaptor & loom which is over £90.

PCB Top
PCB Top

There’s really not much to this adaptor, the only signals that are routed to the ODB connector seem to be the +12v on pin 16, K-Line on Pin 7 & L-Line on pin 15. The main IC here is a CH340 USB-Serial interface, with some glue logic in the form of an LM339 quad comparator.

PCB Reverse
PCB Reverse

The reverse side of the PCB only has the power indicator LED.

Posted on 11 Comments

Jaguar S-Type Aux Heater / Webasto Thermo Top V Part 2 – W-Bus Diagnostics

As I mentioned in the previous post, these heaters have a standard interface that’s used for control & diagnostics, the W-Bus. This is transmitted over the K-Line of the vehicle bus, and all heaters, regardless of firmware modifications done by the various car manufacturers respond to this interface. Official Webasto diagnostic adaptors are available, but these are just a very expensive serial adaptor. A much cheaper option is a ~£5 Universal ODB adaptor.

ODB2
ODB2

Above shows the signals on the ODB connector – the ones we’re interested in here are Pin 16, the +12v supply, and Pin 7, K-Line. Connect Pin 16 to the positive supply to the heater, and Pin 7 to Pin 2 on the Webasto heater. (Valid for all TT-V heaters).

Device Selection
Device Selection

Once these two connections are made to the heater, fire up the Thermo Test software. The screen above will be displayed. Pick W-Bus at top left.

COM Port Selection
COM Port Selection

First thing, connect the ODB adaptor to USB, and change to the correct COM port in Thermo Test. There may be several in the list, but a newly connected USB device should show up with the highest COM number.

Thermo Test
Thermo Test

Once Thermo Test is running, start communications by going to the Diagnosis Menu > Start Diagnostic (F2 keyboard shortcut).

Initialized
Initialized

After a few seconds, communication will be established. This will show faults, if any are present, and allow testing of the heater & it’s component parts. A summary report can be generated with Diagnosis > View Summary:

Diagnosis report                                               Webasto Thermosystems
------------------------------------------------------------------------------------------


Configuration:
--------------
  W-Bus version...............................................................3.3           
  Device name.............................................................X204 SH           
  W-Bus code.......................................................715CC0E73F8000           
  Fuel type................................................................Diesel           
  Circulating pump in control idle period.......................................0           
  Heating duration limitation.................................................255 [min]     
  Factor for shortening of ventilation duration...............................1/1           
  Device identification number..........................................09007236E           
  Dataset identification number.......................................09006806H05           
  Software identification number........................................000000000           
  HW version................................................................51/03           
  SW version..................................................Tuesday/07/04 12.12           
  SW version (EEPROM).........................................Tuesday/07/04 12.12           
  Date of manufacture control unit.......................................27.10.03           
  Date of manufacture heater.............................................04.02.04           
  Customer identification number.....................................4R8318K463AE           
  Serial number........................................................0000123626           
  Test signature.............................................................4B42           
  Minimum voltage threshold....................................................10 [V]       
  Maximum voltage threshold....................................................16 [V]       
  Delay for supply voltage min. detection......................................20 [s]       
  Delay for supply voltage max. detection.......................................6 [s]       

Operating data:
---------------
  Working hours.............................................................44:03 [h:m]     
  Operating hours.........................................................5388:08 [h:m]     
  Start count...............................................................19129           
  Burning duration PH 1..33%.................................................0:00 [h:m]     
  Burning duration PH 34..66%................................................0:00 [h:m]     
  Burning duration PH 67..100%...............................................0:00 [h:m]     
  Burning duration PH >100%..................................................0:00 [h:m]     
  Burning duration SH 1..33%.................................................0:00 [h:m]     
  Burning duration SH 34..66%................................................0:00 [h:m]     
  Burning duration SH 67..100%...............................................0:00 [h:m]     
  Burning duration SH >100%..................................................0:00 [h:m]     
  Working duration PH........................................................0:51 [h:m]     
  Working duration SH......................................................121:10 [h:m]     
  Start counter PH..............................................................6           
  Start counter SH............................................................854           
  Ventilation duration.......................................................0:00 [h:m]     

Error:
------

------------------------------------------------------------------------------------------
12.03.17  17:17:30                                       Webasto Thermo Test  2.16.1

This shows all the important stuff, including running hours. (5388Hrs on this heater!). Most importantly, there are no faults listed.

Heater Running
Heater Running

The heater can be fully tested by issuing a start command from the Command Menu > Parking Heating option. Obviously cooling water will be required for this, along with an external water pump. (The water pump control output on these heaters seems to be totally disabled in firmware, as they rely on the engine’s coolant pump). I used a bucket of water along with a small centrifugal pump to provide the cooling. During this test I noted that the firmware is much more aggressive in these units. The marine versions shut down at ~72°C water temperature, whereas these don’t so the same until ~90°C.

Now I’ve managed to communicate with the heater, I’ll get onto building a standalone controller so I can dispense with the Windows VM for control.