I really appreciate the info on this forum regarding the ECU trouble codes and how to access them. I did exactly as instructed and managed to get 4 error codes from the Check Engine light.

 

My problem is that I'm not sure which of these problems to address first, and would really appreciate some advice here.

The error codes (from my '90 Legacy) are:

11 Crank angle sensor.

13 Cam angle sensor.

23 Air flow sensor.

35 Canister purge solonoid valve.

** Edit** How do I clear the codes? The same thread/sticky? that gave me the procedure was unclear on how to clear them.

Thx in advance for any/all advice.

bob

Well, it depends on the problem you're having. Out of those listed, I'd say that 23 is the worst. It can keep your car from running at all. Try to find one from a junkyard as Air flow sensors that are new are extremely expensive.

 

In order to reset the ecu, you can either pull the ECU/TCU fuse for 45 minutes or pull the negative terminal wire for 45 minutes. After that, reconnect the fuse or wire and turn the car on without any accessories on for 10 - 15 minutes (or if it gets up to operating temperature faster do that). Don't touch the throttle and have it in neutral (MT) or Park (AT). Then you will have retaught the ECU.

 

To clear the codes, you'll need to do something a little different.

 

Josh (Legacy777) wrote up a very good article on how to handle ECU stuff.

http://www.surrealmirage.com/subaru/engine.html

Josh's writeup is where to start. Don't get wound up in the list of codes yet, as some may have been around for awhile (depending on how you got the ECU to cough them up). I had 3 on my new-to-me 90, and after I read them and cleared the codes they have gone away. These were probably from pulling the engine and recharging battery, confusing the ECU.

Well, it depends on the problem you're having. Out of those listed, I'd say that 23 is the worst. It can keep your car from running at all. Try to find one from a junkyard as Air flow sensors that are new are extremely expensive.

 

In order to reset the ecu, you can either pull the ECU/TCU fuse for 45 minutes or pull the negative terminal wire for 45 minutes. After that, reconnect the fuse or wire and turn the car on without any accessories on for 10 - 15 minutes (or if it gets up to operating temperature faster do that). Don't touch the throttle and have it in neutral (MT) or Park (AT). Then you will have retaught the ECU.

 

To clear the codes, you'll need to do something a little different.

 

Josh (Legacy777) wrote up a very good article on how to handle ECU stuff.

http://www.surrealmirage.com/subaru/engine.html

 

Thx much, both of you... Forgive my ignorance, but what is the difference between "re-setting the ECU" and "clearing the codes"? Isn't that the same thing?

Apparently not. Although maybe not accurate, I view it as resetting short term memory (current codes) and long term, saved memory (stored codes).

Clearing the codes just clears the trouble codes. Resetting the ECU all together resets all the settings that have been learned on the ECU since it was last reset (which for most cars was at factory).

Resetting occurs pretty much anytime ECU loses battery power for more than a few minutes, which on these cars would be several times over the years.

Resetting occurs pretty much anytime ECU loses battery power for more than a few minutes, which on these cars would be several times over the years.

It takes 30-45 minutes to completely erase the memory of the ECU.

 

Remember, if you reset it, the ECU has to relearn the system. If you clear the codes, you don't have to relearn anything.

After all of the above and probably least important, for the purge solenoid code 35, check the solenoid with an ohmeter. If it reads out of range grab one at a junkyard. I couldn't find a new one reasonably priced. You could stick a resistor in there to fool the computer until you find a good solenoid.

Thank you all very much for the great input....

code for both crank and cam- did the t. belt jump time?

code for both crank and cam- did the t. belt jump time?

 

that was my first thought. what's the car doing?? why did you check the codes in the first place? did the light come on or did you notice a difference in how it runs / drives?

 

leave the battery cable off over night, run the car for a day and then check the codes. anything that comes up then will be current.

that was my first thought. what's the car doing?? why did you check the codes in the first place? did the light come on or did you notice a difference in how it runs / drives?

 

leave the battery cable off over night, run the car for a day and then check the codes. anything that comes up then will be current.

 

I have no idea if the t-belt jumped timing, but guess I'll have to have a Subaru dealer check that...

I checked the codes because the Check Engine light was on/off/on/off while driving. It can come on with the engine fairly cold and when hot. Doesn't come up as soon as the car is started.

thx

bob