OBD port pinout

**PaddyB** · 08-07-2010, 03:45 PM

Been looking at the OBD port on my PFL & I'm curious about the pinout.

Pins 4, 5, 7 & 16 are there which means it can talk ISO9141/14230. Pin 1 is also present & is mentioned in the specs as propriety - in our case for displaying error codes when grounded.

Pins 9, 11 & 12 are also present. These are not mentioned in any specs I've seen. Does anyone know what they do ??

Cheers.

**foxdie** · 08-07-2010, 04:07 PM

It's funny you should be bringing this up now, I've been doing some research into this myself the last couple of days, I'll share my findings;

First of all, here's what I believe to be the pinout from my trawlings of various forums;

Pinouts for the diagnostic connector on the car:

Suspected L-Line (ISO9141-2) - Goes to C3P6 on EFI ECU - Grey with red stripe
N/C
N/C
GND (Chassis) - Black
GND (Signal) - Black
N/C
K-Line (ISO9141-2) - Goes to C3P12 on EFI ECU - Red with white stripe
N/C
ETACS Terminal - Green with orange stripe
N/C
Unknown - Yellow with dark stripe
Unknown - Yellow with dark stripe
N/C
N/C
N/C
+VE (12V from car) - Red with black stripe

There are 2 important points at this stage:

We're told to short Pin 1 (suspected L-Line) to Pin 4 (GND) to get EFI (engine) diagnostics mode, I currently believe this is WRONG as it's mentioned in numerous forums to move Pin 1 on the cars connector to Pin 15 on the cars connector, and Pin 15 is typically the L-Line as part of the ISO9141-2 standard.
Some cables come with Pin 9 connected to Pin 15, you MUST remove this pin from the cable (or the car, but highly recommend the cable), this has been known to DISABLE THE BRAKES on the car by confusing the ABS system

I've tried the inverse of the first bullet above (I tried "adding" pin 1 to my generic vag-com cable and bridging it to pin 15), I didn't have any luck though but I now suspect that to have been a bug in EvoScan v2.5, I'm going to try with v2.7 Beta later tonight.

I have more information, I'm digging it up now, I'll add more to this post when I've got more

**foxdie** · 08-07-2010, 04:10 PM

Here we go, taken from My Rolling Road (Evo specialist forum), pin 9 is for the ETACS terminal, I've amended my post above.

I'm not sure why this would relate to our cars though, I don't think we have ETACS (Electronic Time and Alarm Control System)?

**PaddyB** · 08-07-2010, 04:23 PM

I was wondering about ETACS too. I've read that on MMCS equipped cars ETACS is a system that allows the user to change things like rear intermittent wipe period, how long the lights stay on, etc. Makes sense for it to be pinned out.
Well kind of.

On later MMC cars, ETACS can also control the windows/sunroof/mirrors. MMC ETACS is also found on Hyundai & some Kia cars too. It looks like it might be interesting ....

**foxdie** · 08-07-2010, 04:25 PM

And some further musings on why we shouldn't be bridging Pin 1 to GND;

My reasons for looking into the above was because I was frustrated at my generic cable not being able to log AYC / ABS.

It's well known that OpenPort 1.3U cables will connect to the ABS / AYC system, and after looking at the schematics for such a cable I realised my generic VAG-COM cable was nearly identical (same chipset, near identical layout etc)..

Another thing I noticed was that some people were noting that they couldn't log until they'd moved the wire in Pin 1 to Pin 15 on the cars diagnostics connector, and after looking at ours I realise we may be on the same lines.

A couple of months ago I tried bridging Pin 1 to Pin 15 on my VAG-COM cable (as it's easier to do than the car diagnostic connector), but when testing it I found I could neither log the AYC/ABS systems or the EFI (engine) system either so I reverted my cable back and went back to the drawing board.

I've since learnt that the version I was using (v2.5) had quite a few people bitching that they couldn't log AYC / ABS with their OpenPort 1.3U cables, and subsequently a couple of revisions later the problem is supposedly fixed, so I've upgraded to v2.7 and will try it later this evening and report back

Ps. There's confusion over upgrading, Hamish (the EvoScan developer) implemented new licensing methods, you don't need to purchase the software again to get an upgrade, you just need to file a support ticket on his brand new but hidden website with your old key / registered email and he'll issue you out an updated license key

**Nutter_John** · 08-07-2010, 04:28 PM

or you just could goto

www.evoscan.com

**foxdie** · 08-07-2010, 04:47 PM

Originally Posted by Nutter_John

or you just could goto

www.evoscan.com

Ahh he has that many of the damned things

**foxdie** · 09-07-2010, 12:16 PM

Okay small update, first I'm bumping because I've updated my first post to include an image of the OBD connector on the car, and wire colourings.

I tried moving pin 1 to pin 15 and had no luck, EvoScan v2.7 just wouldn't connect. When it was trying to connect, the dash lights started flashing briefly, then stopped.

I guess I'm just going to have to bite the bullet and buy a 1.3U cable.

**foxdie** · 09-07-2010, 12:31 PM

Referencing Kitty's VR4's awesome EFI ECU Pinout thread, I've updated the pinout list above.

**foxdie** · 09-07-2010, 03:22 PM

Hmm, hopefully some more interesting titbits, with more "thinking out aloud"

Referencing a couple of Kitty's VR4's pinouts for AYC systems, there's mentions of the 2 lines, for this example we're using the ASC-AYC pinout research, on the 12 pin (3rd / C3) connector, we've again got a mention of the 2 MUT-II cables, RED-WHITE (C3P2) and GREY-RED (C3P8), I guess it makes sense that all relevant devices use these 2 lines to communicate with the MUT-II.

What's interesting is the K-Line (RED-WHITE) is listed as "Diagnosis data input/output", and the L-Line (GREY-RED) is listed as "Diagnosis change input", which would make sense that you'd use the second line to select which ECU you wish to speak to if you're using a common line for data exchange.

So bringing this line low (GND'ing it) allows you to communicate with the EFI ECU, I wonder what happens if it's held high? Personally I don't think it's that simple, but I'm willing to try for science at the weekend

**Davezj** · 09-07-2010, 03:50 PM

interesting stuff, but holding pin 1 high will select which ECU?

you have a few to choose from ayc, tcu, abs, SRS.

**foxdie** · 09-07-2010, 03:59 PM

Originally Posted by Davezj

interesting stuff, but holding pin 1 high will select which ECU?

you have a few to choose from ayc, tcu, abs, SRS.

Yeah that's a given! I was just musing.. "if holding it low selects EFI, what does holding it high get?"

I guess I need to get my hands on an OpenPort 1.3U and a 2 channel logic analyser / oscilloscope or something

Edit: WOO! 1337 posts

**Davezj** · 09-07-2010, 07:29 PM

you may well find that if what suspect is true about the single wire data in/out is occurring, then pin 1 is actually and address line and it is just convenient that the engine ecu is at address 0000.

**PaddyB** · 09-07-2010, 08:29 PM

Been a looking.

Pins 1 & 7 go to a lot of places.
Engine ECU: pins 56 & 62 resp.
A/T ECU: pins 23 & 63 resp.
TCL ECU: pins 1 & 14 resp.
ABS ECU: pins 14 & 7 resp.

Pins 1 & 11 goes to A/C ECU pins 18 & 17 resp.

Pin 1 also goes to keyless entry ECU, pin 7.

Pin 12 is a single wire interface to the MUT-II connector.

Pin 9 goes to the ETACS ECU, pin 8. Thats the thing that does the ding ding ding when you've left your keys in. It also switches interior lights off, the intermittent rear wipe intermittentness & it's also plumbed into the sunroof (if fitted), power windows, central locking & lots of other stuff.

So my best guess ATM is that:
pins 1 & 7 is an addressable bus,
pins 9 & 12 are single wire interfaces to ETACS & MUT-II resp.
pins 1 & 11 go to the aircon but can't thhnk how that might work
pins 4 & 5 are ground
pin 16 is 12V (10A fused)

**PaddyB** · 09-07-2010, 09:09 PM

There's also the 'other' diagnostic connector to muddy the water, the 12 pin one.

Reading on ISO 9141: the K line (pin 7) is a single wire addressable bus. Any device can talk & listen on this line. The L line (susp pin 1) is exactly the same as the K line but only external hardware can talk on this line.

What I'm trying to achieve is a OBDII data logger; thus far I've acquired an embedded micro with UARTS & ADC agogo. Seeing as ISO 9141 is not an open protocol I'm considering getting an ELM323 to do this bit.

**scott.mohekey** · 10-07-2010, 12:19 AM

My thoughts are that pin 1 is a 'bus enable'. Holding it high will have the same effect as not doing anything I imagine, unless it floats (which is unlikely). It's possible it needs to be pulsed to select different ecus. But from what Paddy says above about pin 7 being addressable, that pin is simply bus enable.

**PaddyB** · 10-07-2010, 01:26 AM

I'm building on fox's hypothesis that pin1 is really a relocated pin15 (is his fault really)

If we agree that pin 7 in the ISO 9141-2 K-line then all devices on that line can talk & listen to each other. I can't find out [yet] if a packet header states the source/destination - what I've read (which isn't the spec) suggests that it's some time multiplexed system. It's supposed to be the same as RS232, etc. except levels so it should be sniffable.

The true nature of pin 1 is the issue - if it is pin 15 then why not put it there. Pin 1 is reserved for proprietry use according to the spec so what's going on there is not in the public domain. All I know is that it goes to every ECU available, even more that pin 7. Might be bus enable - very possible - but I'd imagine that these systems would chatter with each other regardless of the state of pin 1

I have 'scope, openport 1.3 & evoscan - I'll endeavour to have a go this w/e. If it carries the same signals as pin 7 (the K line) during initialisation then it woudl suggest it's the L-line.

**scott.mohekey** · 10-07-2010, 02:25 AM

Sorry, when I say bus enable, I mean for diagnostic purposes. I.e. it would be my guess that during normal operation, pin 1 is always floating/high.

**foxdie** · 10-07-2010, 09:50 AM