riofrio

I was just reading the thread "SE Error Code Write-Up" by gsl-se addict:https://www.rx7club.com/showthread.p...ght=remove+ECU

I wanted to ask 2 things:

1)Does the error checking procedure require the engine to be at WOT?

2)If I replace the ECU, do I need to drain the battery before doing so?

Thanks.

gsl-se addict

iTrader: (3)

1. No, the engine does not have to be at WOT. Actually, the enigne should not even be running with this procedure. Just connect the lights and turn the key to 'ON' but not all the way to start.

2. If you do need to remove the ECU. You really don't have to do anything special. I would disconnect the negative battery cable as a general rule. The newer ECUs needed to discharge the internal charge using some proceedure because they stored the codes in memory. (This means that even if you fixed the problem that was causing the code, the error code would still be present). Often you would have to clear the codes by disconnecting the battery and holding down the brake pedal or something similar each time you did something to try to fix the code and then check for codes again. The SE ECU does not store codes, so if any exist, they will go away once the problem is corrected.

Please feel free to PM me if you have any other questions. I can also go over checking the AFM, ECU voltages, etc.

Kent

riofrio

Thanks man! I'll get on it this weekend and will let you know if I have any other questions.

riofrio

Ok, so I did the error code testing, and found an interesting thing...

hooked up the LED to the test connector, turned the key to 'on', LED lit for about 3 seconds and then stopped. Since I had been suspecting that the ECU was defected, I started unhooking things to see if the errors would show. First unhooked the TPS, and the correct light pattern appeared on the LED, so I hooked it back up. Then, tried the AFM... same deal. BUT, then I unhooked the O2 sensor.... and nothing! In other words, the computer is telling me there's nothing wrong with the O2 sensor even if the O2 sensor is not even plugged in! Shouldn't it display the O2 error pattern on the LED?

The O2 sensor is brand new, and it makes no difference in the idle whether the sensor is plugged or unplugged.

I tried swapping ECUs with one I found from an old SE, but this one didn't even light the LED on the 'key on' position, which means it's not working, right?

I also swapped AFMs, and it did make a difference. Idle quality is a lot better, and better yet, the quality of deceleration improved tremendously (which I don't understand why).

I'm trying to pass emissions, and I think the O2 sensor deal might be the real issue here, but I have no idea what to make of it.

Maybe I should find an ECU that works and see if it changes anything?

riofrio

...anybody?

gsl-se addict

iTrader: (3)

Okay,

I checked the FSM, and it says for the O2 sensor code, the engine has to be run at 2,000 rpm with the O2 sensor disconnected. You can run the engine while doing the error checking, I usually say that you don't need to because only the O2 sensor code requires it. You could leave the LED plugged in all the time and mount it somewhere if you wanted. It won't hurt anything.

I don't think that the O2 sensor would cause the problems that you are having since it only is really used during steady state conditions, like criusing at a constant speed. The O2 sensor is usually ignored at WOT, during accelerations, and many times at idle.

At idle, it is usually ignored because of a couple of reasons
-First, at idle the O2 sensor may not be hot enough to operate correctly
-Second, for most engines, the idle should be a bit rich to idle the best idle. Since narrow band O2 sensors, like ours, can only work near stoichiometric conditions (14.7:1 for gasoline) , they only give a linear output near 14.7:1. So they basically can tell you if you are at 14.7:1 or tell you if you are more rich or more lean than 14.7:1, but not by how much.

Anyway, I think that your ECU is probably okay. I am glad that you were able to follow the write up and were able to get the tester working. Do you have access to a multimeter? The next thing I would check is the voltages at the ECU. You could also use the multimeter to check the output of the AFM.

I think that it is pretty cool that these cars had this error code checking. But as you see, it is pretty simplistic and can only diagnose only a few problems. I think the miata has about 72 possible error codes compared to our 6.

Let us know how it goes.

Kent

riofrio

Thanks Kent, that was helpful... good to know too!
The other thing that worries me a little bit (and I'm not sure if it should) is the TPS. When I go through the standard adjustment procedure, I can get the single light to light, but no matter how far clockwise I turn the screw (heck, even if I push the TPS in all the way with my finger), I will never see both lights on.

gsl-se addict

iTrader: (3)

For the TPS, both lights should come on if the plunger is pressed in. First make sure that both lights are working. Try swapping the lights around to make sure that the bulb is good and the wiring is okay. If both lights work and the wiring is correct and you still have this problem, you may have a bad TPS. Try unplugging the TPS and measure the resistance between each "eye" of the connector and its "mouth". The connector looks something like:

| |
_

The resistance should be like 1kOhms - 5kOhms as you move the plunger in and out. Do you have the FSM? You can download it at:

http://www.wankel.net/~krwright/cars/rx7/85_manual.html

You want chapter 4B. Keep us updated on the progress.

Kent