1997 mk3 No OBDII connection to ECU

[andy_k]

I've tried the obvious removing the K Line from the back of the stereo and disconnecting the ABS pump but stilll my OBD II reader can't pick up a connection to the ECU - it works fine on other vehicles so the reader is not suspect.

Any ideas?

[lee1989]

Not sure if urs will be the same mate but it happened to mine i bought 2 and it turned out i blew a fuse lol worth a look 

[itavaltalainen]

mk3 golf is not obd 2 - which adapter do you have?

[andy_k]

I thought Golf 3 was OBD 2 after 1996

It has the plug next to the ashtray

Using an elm 327 interface

[gazareth]

why you need to plug it in anyway?

[andy_k]

Curiosity

It runs a little rough/underpowered around 2000 rpm so before I put it on a gas analyzer (which I don't own so would have to pay for) I was looking for fault codes - particularly those that mentioned Lambda or MAF

[itavaltalainen]

Nope, Mk3 Golf is KKL (OBD1) not OBD2 - it only has the same plug as OBD2.
This forum here is particularly 'bad' for people calling it OBD2 despite it not being that at all; at best you could call it OBD1.5 .... The protocol is STILL the same as it was for the early Mk3 that had the 2x2 connectors - only the shape of the connector has changed.
Hence the ELM327 adapter unfortunately won't work on your Mk3 Golf.

You need a KKL Adapter that speaks KWP-1281 (most of them also do KWP-2000) and vcds lite.
Only VWs from around 2000 (Diesels mostly) and petrols about 2 years later can deal with OBD2 - however OBD2 is not as powerful as the VW protocols, it can only access exhaust (engine) related issues.
For the full array in a VW you would need KKL (or on later cars - mk5 golf on you need CAN).

Go get yourself a AutoDia K409 or similar if USB is desired or better; get a serial adapter ELV VDA100 (and if your PC does not have a serial port anymore get yourself a Brainboxes US-101 USB<=> RS232 converter).

What year and engine code is your Golf?
Could also be knock sensor that's acting up - had that on a 94 2E once.

[andy_k]

It's a 97 2.0L GTi with an AGG engine

[itavaltalainen]

check ignition coil for cracks,
check knock sensor for cracks in insulation,
have a look at air mass sensor (clean only with 99.9% iso propyl aclohol and a cotton bud; rinse copiously with IPA after using cotton bud, allow to dry before putting it back in or better spray dry with dry air out a can),
clean throttle body,
measure temperature sender at 3 points (measure temp in expansion tank) and see if response is within spec (how to is here) or alternatively check temp with VCDS,
check lambda is working with VCDS measuring blocks (you could also connect a mini DSO, i.e. pocket oscilloscope to the lambda - they are about 50£ on ebay)

[andy_k]

Coil is fine, MAF has been cleaned with spray MAF cleaner and then dipped in IPA and blown dry with compressed air from a can like you suggest. Throttle body has been cleaned, new HT leads. plugs, rotor arm, dizzy cap (normal service stuff really).

Next step is to replace the MAF with a known 'good' one and inspect the knock sensor (are there on or two?)

I'll need to get it plugged in somewhere to read/clear fault codes after that - hence the question about OBDII

Thanks for your input - it's much appreciated