OBDII Socket on W163

[myblueml]

Hi All

When I checked the brakelight switch I took a look at the OBDII socket, There are a few more wires connected than I wouild have expected.

This is what I found.

OBDII Socket pinouts

1. -
2. Bus positive Line of SAE-J1850
3. -
4. Chassis ground
5. Signal ground
6. CAN high (ISO 15765-4 and SAE-J2234)
7. K line of ISO 9141-2 and ISO 14230-4
8. -
9. -
10. Bus negative Line of SAE-J1850
11. -
12. -
13. -
14. CAN low (ISO 15765-4 and SAE-J2234)
15. L line of ISO 9141-2 and ISO 14230-4
16. Battery voltage

What do pins 1, 3, 8, 9, 11, 12 and 13 do on the socket and why are 2 and 10 not connected.
I put a MaxScan GS500 on the car and it would read live data and said tha there was 1 code stored but it will not tell me what it is.

Any ideas or info apreciated.

Cheers.
Pete.

 

[lynall]

Switch under a tenner from merc.



Lynall

 

[richard]

6 & 14 arent connected as car does not have CANbus (its optional for OBD-II/EOBD, and OBD-II/EOBD only cover emissions related control units)
2 & 10 are for J1850 which is the protocol that Ford/GM (2 subtly different varieties) chose to use for talking to the emission related control units
The rest of the German manafactures when with K line protoocol (or K/L) which uses 7 and sometimes 15. (dont think MB ever used the L line, but VW did)

The other pins are all the other control units in the cars. OBD-II/EOBD define those pins as manafacurer use, and Merc connect all the other control units on the car. Technically they could put them all on 1 pin, but have chosen not to, presumably because they tested interaction between the units in the configuration they chose.
- over time more and more units have become configured via CANbus rather tha discrete K line type control. for instance my W164 only has the power (4.5.16) and CANbus lines.
Mercedes (before complete CANbus) use pin 8 for switched ignition. And before OBD-II put one control unit on a signle pin in the 38 pin connector that was under the bonnet (on W210 and before)

The maxscan (assuming its a OBD/EOBD code reader) is only reading the emissions related control units (On W163 ML that is the engine management system only), and if it can see a code it should be able to read it and tell you what it is !

R

 

[myblueml]

Fitted a new brake light switch and up to now not had a recurrence of the initial problem of ABS ESP etc. It was a piece of cake to fit once I knew there was a latch to press to get it out. I had another look at the OBD socket and I can confirm that all pins except 2 and 10 are wired. so what they do is a mystery.

cheers

Peter.