1995 Subaru Legacy (250T) Service Engine Light

[DBF498]

I've got a 1995 Legacy 250T (BG9) with an automatic transmission and right hand drive that probably shares more with the Australian market than the US and am having a little trouble with it. The service engine light comes on, not a hard light (on all the time) which is leading me to believe it's not a serious problem but one I should address soon. From what I've read on this forum and other places the engine management system is obd2 compliant but has a 14 pin plug instead of the normal US market obd2 mandated plug. There are no labels or badges telling me what system is on this car so I've crawled around it and am pretty confident it is not obd1. I've got a cable, OBDLink SX, and software, OBDWiz, to read for a 1996 and up odb2 equipped vehicle but was wondering if anyone knows of an adapter to connect an OBD2 cable to the DLC on my car. I bought it right from http://www.scantool.net/ and one of their forum moderators states my car is not odb2 without any hesitation or reasoning. So, I thought it would be best to ask the folks here instead. Does anyone have any experience with pulling codes from this generation legacy? If I can't use what I have what code scanner is recommended? Mind you, I have unlimited wants and limited resources to pay for them with so I need to maximize my purchasing power...translation...I'm on a budget.

Here is a picture of what I'm assuming the DLC plug is. I've seen IPBs, for the 1996 and later, which show a DLC and OBD2 plug, behind an access door, and I'm assuming since there's no OBD2 plug the pictured plug is the DLC; if this isn't the case educate me on what to look for.

http://i1205.photobucket.com/albums/bb431/dbf498/fb81b2cd.jpg

[chuckthefuk]

Oh wow this ones going to be fun :-D

Its nice to see that you have done a fair amount of research so far and you are pretty much bang on about most things.

North America BD/BK/BG chassis did have the OBDII port located on the left side of the steering column

http://img27.imageshack.us/img27/3467/obdport.jpg

There has been some debate about North American OBD generation switch over dates in all Subaru models but general consensus is that in 1996 OBDII became mandatory for all vehicles but prior to that manufactures would test OBDII technology on pre-96 vehicles.

Usually its as easy as looking under your hood and finding the emissions label.

OBDII DLC's are 16 pin however the one that you have posted is 14 pin... Now a general search online for OBD1 vs OBDII yields 9 pin to 16 pin converters.. This is not helpful. More research would show that between OBD1 and 2 there was OBD1.5 and yet this is still not yielding proper results.

Now I have only spent abut 15 minutes on this subject but I find converts that go from 14 pin to 16 pin

*warning* this is for a nissan adapter! The pinouts may be different. *NOTE* nissan supplies many electrical components for FHI (Subaru)

https://sl-i.net/FORUM/images/imported/2012/08/sku_116340_1-1.jpg

or

http://www.obdreaders.com/Nissan+Consul ... 14+Pin/21/ (http://www.obdreaders.com/Nissan+Consult+Diagnostic+Interface+Tool+14+Pin/21/)

So this would lead to me to believe that your Legacy uses OBDI or II or I .. hmmmm

... Troubleshooting OBDI codes can be found here --> http://www.troublecodes.net/Subaru/

I can not give you any more information then this, I hope this helps you.

-Chuck

[DBF498]

Thank you for the kind words. I didn't want to present a challenge without giving as much of the details that I could. Just so we understand one another this is a car in Japan not in the US. So, a lot of what is found on the US version may not be on the one I have. I think there was a thread floating around on this forum that basically suggested most of the Legacy's with an automatic beginning about mid 1995 were obd2 compliant but those with manuals still had obd1 on board. I'm only speculating but I'm thinking that may be due to the automatic transmission being controlled by the computer.


OBDII DLC's are 16 pin however the one that you have posted is 14 pin... Now a general search online for OBD1 vs OBDII yields 9 pin to 16 pin converters.. This is not helpful. More research would show that between OBD1 and 2 there was OBD1.5 and yet this is still not yielding proper results.
What you found is exactly what I found. There's almost no information on the second generation legacy (BD/BK/BG) outside the factory. I've been able to find schematics for a 1996 and later, wiring is different colors, and is virtually useless.

Well, like I said I've crawled all over this car and I'd be willing to bet a frosty adult beverage it isn't odb1. It could be obd1.5 but I'm not wholly convinced it is. If memory serves, odb1 wasn't designed to handle the volume of information from multipoint (sequential port) fuel injection systems and distributerless (sp) ignitions. Oh, this car does have two O2 sensors one before and one after the catalytic converter. I'd agree with you on having the emissions label under the hood and that was one of the first things I looked for, well, at least the Japanese version of one but one wasn't there. The picture you've attached is the one I've seen before and that was the one I was referring to. I think the one I saw was for a right hand drive vehicle, which mine is, as well but I could be mistaken.

I didn't know Nissan supplied electrical components to FHI (Subaru)...hmmm...very interesting. I saw the Nissan 14 pin plug and wondered if this was the same type of plug. I'm reluctant to use a cable for a Nissan because with my luck the pinout would be different which could very well equal a very bad day.

I found this open end cable and pinout I found at OBD2cables.com the other day and wondered if it would work.

http://i1205.photobucket.com/albums/bb431/dbf498/c776eb61.jpg

http://i1205.photobucket.com/albums/bb431/dbf498/1aa3cd84.jpg

I thought that would be a good start to make my own cable...if I could find a wiring schematic for the DLC on my car I'd be golden.

I think I might find Hen's teeth before I find a schematic.

[hansvonaxion]

So have you checked the code by just plugging the plugs together yet?

[DBF498]

Which plugs are you referring to?

[hansvonaxion]

The two black ones, plug them together and switch the ignition on, long blinks of CEL for 10's short blinks for 1's... e.g. BLINK BLINK blink blink blink = 23. Worked for me when the TPS sensor was playing up.

http://legacycentral.org/library/literature/codes.htm

That site doesn't have all the codes, at least for the TT, but you can double check with a local Subaru dealer if you want to make sure. In fact they'll read it for free, when I went in and told them the code they took the car out the back to check anyway before giving me a quote to swap the sensor.


Underneath the steering column is a wide rectangular piece of plastic, the same color as the dash, which has a tray marked 'TRAY.' This large piece is held to the underside of the dash with a bunch of screws. Remove these screws and remove the plastic piece. Now there will be a bunch of wires for you to see. To the left of the steering column (at least in left hand drive cars) somewhere probably tucked away will be a bundle of wires with two pairs of electrical connectors which are disconnected. One is black and connects one wire to one wire, the other is green and roughly 'T' shaped, this one also connects one wire to one wire. With the car turned completely off, connect the black connector. Next, turn the ignition to 'ON' but do not start the car. The idiot lights in the dash will come on, and some may go out after a few moments. Watch the 'check engine' light and maybe have something you can write on to remember the codes. If there is a fault code in the ECU, the 'check engine' light will begin to flash in a particular manner. The codes range in number from 11 to 52, so we know that they all will be two digits. To signify the tens place of the number, the 'check engine' light will flash a long (1.2 seconds) flash. The single digit will be a short (.2 seconds) flash. Each flash within the same code will be separated by .3 seconds. Each error code will be separated by 1.8 seconds. Don't bother trying to time all these, just watch the light and you will begin to understand. Once the ECU has flashed all stored codes, it will loop through and repeat them. Now, for example, you see two long flashes followed by two short flashes. This means you have a code number 22. By looking at the following chart, we see that 22 is the code for the knock sensor. Once you have read and recorded all faults, turn the ignition off and disconnect the black connector.

[chuckthefuk]

I also posted this at the end of my 1st post.

https://sl-i.net/FORUM/images/imported/2012/08/subarudlcgif-1.jpg
http://www.troublecodes.net/Subaru/

-Chuck

[chuckthefuk]

And here is the OBDII pinout for a subaru
http://www.evoscan.com/technical-vehicle-manuals/136

[DBF498]

This is very similar to how I would pull codes from my old OBD1 equipped 89 Chevy Pickup. I'll give try this and see if it works.


The two black ones, plug them together and switch the ignition on, long blinks of CEL for 10's short blinks for 1's... e.g. BLINK BLINK blink blink blink = 23. Worked for me when the TPS sensor was playing up.

http://legacycentral.org/library/literature/codes.htm

[hansvonaxion]

I'm not sure but the second gen might not use OBD at all, it might be Subaru's proprietary system.

[chuckthefuk]

I was thinking the same thing when I found the Nissan info. My first post shows a secondary connector for subaru select monitors. Hmmmmm

[DBF498]

Well gents, I did what hansvonaxion recommended and connected the two black connectors under the dash. This is what I came up with; error #22 and #23.

The way I understand it from the Legacy Central ECU codes this is what I came up with.

22 = Knock sensor = Abnormal voltage produced in knock sensor monitor circuit = Sets in regular fuel map and retards ignition timing
23 = Air flow sensor = Abnormal voltage input entered from air flow sensor = Controls the amount of fuel (injected) in relation to engine speed and throttle sensor position

I was thinking that there might have been an issue with both of these items before I connected the two plugs. At low speed, under 2500 rpms, the light would come on and stay but above 2500 rpms the "service engine" light would extinguish so I of the assumption that the Air Flow code lent some credence to my thinking.

Has anyone had a similar issue with their air flow sensor? I'm tempted to clean it and see if that will make a difference. I replaced the air filter on it earlier and it had some serious gunk on it. A few particulates may hit the probes in the Air Flow sensor...then again...I could be speaking out my back side...:-)

The knock sensor seems cheap enough to replace. It's got about 146K and 17 years on it so it could be time to replace it. The Air Flow sensor on the other hand may be worth cleaning first.

I'll let you gents know if that fixes the "service light" issue. I'd still think accessing the ECU for a more thorough analysis of the engines overall operation is necessary. I'll also need to clear the codes while I'm at it.

[DBF498]

Well...it's time for an update. After the last post I got my hands on some MAF cleaner, some time ago almost impossible to find in the BX, and commenced to clean the MAF sensor. The initial cleaning solved a lot of problems and the car ran much better. However, the service engine light still came on when the AC was running. The other day the new knock sensor in and I installed it. The old one's plastic outer shell was cracked in multiple places, see attached photos, and this could have caused it to give erroneous signals. So far after replacing it the engine light has not come on. The biggest test was when allowed to idle for 5 minutes with the AC on the service engine light would come on before, now, no light. Although I feel this solved the majority of my car's ills I went ahead and replaced the MAF sensor as well. I got a new one pretty cheap, less than the knock sensor, and so far it seems to be running much better. I guess time will tell.

http://i1205.photobucket.com/albums/bb431/dbf498/messagepartguidmessagepart3AINBOX2F-4.jpg

http://i1205.photobucket.com/albums/bb431/dbf498/messagepartguidmessagepart3AINBOX2F-3.jpg

[hansvonaxion]

Good to hear.