Can't reset ECU?

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DLC
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Can't reset ECU?

Post by DLC »

After pulling a Knock Sensor code, i replaced it with the new version. To my dismay, two attempts to reset the ECU and clear the codes have been unsuccessful. I've tried disconnecting the negative battery terminal for about 45 minutes, then the positive last night for 8 hours or so.

Codes still came up after reconnecting the battery...

Is there any other way besides having someone with a Select Monitor reset them? The instructions i have on my own page about resetting with the connectors are a bit confusing, and i'm wondering if anyone has ever tried that method.

Dave
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Post by boostjunkie »

I've tried the "other method" of connecting the connectors under the dash as described by Josh's site. I don't remember off-hand but you can find it on his site.

I connected whatever needed to be connected, started the car, and then drove around. I didn't abide by the keeping it in the 20mph range, just did some city driving . . . once I drove at a fairly constant speed for about a mile, the CE light blinked repeatedly at a constant rate, indicating the ecu was cleared.

I was told that the battery method was a more sure-fire way to do the reset, however. Have you checked all of the connections to and from the knock sensor? I would suspect that if you reset the computer via the battery-dance, that there might be a wiring/installation problem. *shrug*
[url=http://www.angelfire.com/md3/91turbolegacy/images/On_the_Lawn.jpg]1991 Legacy Turbo (RIP)[/url]

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Post by DLC »

I'd suspect the wires from the knock sensor, if there wasn't a MAF and Cannister Purge Solenoid code in there as well.

I don't know if my codes will reset with the "driving around method" because i never connected my neutral sensor. No harm in trying though, i suppose.

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boostjunkie
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Post by boostjunkie »

The fact that you have all three of those codes showing immediately after installation for the knock sensor (I'm assuming these other two codes weren't present before), leads me to believe that it is, in fact, a wiring problem in the knock sensor, or perhaps a faulty sensor.

When I accidentally disconnected the MAP sensor wire I ended up having four codes show up. MAF, MAP, knock, and something else. I think the ecu is trying to assess the different readings and if one is off, and they are all interrelated somehow in engine function, the ecu doesn't know which sensor input is correct. It throws a code for everything!

I would definitely look into the connections again.
[url=http://www.angelfire.com/md3/91turbolegacy/images/On_the_Lawn.jpg]1991 Legacy Turbo (RIP)[/url]

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Post by vrg3 »

Dave, I'd definitely suggest using the method on your web page. Some ECUs (I don't know about any particular ones) do store trouble codes in nonvolatile or semi-nonvolatile memory, so a battery disconnection doesn't delete them.

There's also a bonus with the "proper" memory clearing procedure: it has a self-diagnostic built in. Basically, the ECU does some active checks for problems. Only if the problems are actually gone will it clear the codes. If your neutral switch is missing, but the other problems aren't still there, it should clear the other codes, I think.

It's not as complicated as the instructions sound. Just hook up both sets of connectors (the green pair and the black pair), and turn the ignition on. You'll hear various solenoids cycle and stuff as the car tests them. Then start the engine and drive for a while normally. The CEL start blinking after a while.

If it's making 1-second long blinks about a second apart, then the codes are cleared. If it's blinking a trouble code, then it still found that problem.
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Post by DLC »

boostjunkie: those three codes were there before the knock sensor replacement.

vrg3: i think you're probably right, maybe mine has a later ECU or some wierd thing that needs to be reset with the D-Mode connectors of SelectMonitor only.

I'll try the drive method.

Dave
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Post by Legacy777 »

Yeah....you need to do the green & black connectors together.

Here's the exact procedure....it's from the FSM

ECU clear memory procedure is as follows for auto and manual transmissions:

With engine at operating temperature, turn engine off. Place gear shift lever into park (auto transmission cars only).

Locate the two ECU check connectors, for most cars they are located under the steering column and consist of a black plastic male and female connector, and a green male female connector. The exact location of the connectors varies with the different year models, but generally they are located under the steering column on the drivers side.
NOTE: sometimes they are still taped over with some small amount of plastic tape, so look hard, they will be there!
With the ignition OFF connect black to black and green to green.

Turn on ignition, do not start the engine, (and for auto transmission, cycle the gearshift lever from park to neutral and back to park ), depress the accelerator pedal to full throttle and hold for a few seconds, and then release. Start engine and then drive for at least one minute, keeping road speed above 10 mph.

ECU is now re-set.

At this point the check engine light should start to flash the all clear signal (steady 1/2 second interval flashes). If the check engine light does not flash, or indicates some other sequence, there is a fault present in the system, and should be checked for necessary repairs.

Once done, stop the car and turn off the engine.

Disconnect the plugs.
Josh

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Post by DLC »

I did that. I've got 35 (canister purge solenoid) and 51 (inhibitor switch).

That 35 is getting on my nerves, and i'm not sure what to do about the inhibitor switch.

Does it still reset the ecu, even if it pulls codes?

Dave
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Post by Legacy777 »

Dave.....I'd suggest to just go ahead and replace the canister purge valve. I think you could probably get one for about 70 bucks new from an online dealer. Installing it isn't that difficult. The other option would be to put a resistor inline to trick the ECU into thinking it's there and just chillin. You of course then don't have a functioning evaporative emissions system.....but ya know.....

I'd probably just replace it.....but that's me.

The inhibitor switch. I'll take a look at my FSM's and see what we can do about that. If I forget and don't reply in a day or so......PM me or do something to get my attention :)

"Does it still reset the ecu, even if it pulls codes? "

Which connectors did you connect? both sets?

Here's a fine a line, which I have been trying to find out, and after looking at the select monitor....I think I have a grasp or good working theory.

Resetting the ECU and clearing the codes are two procedures that are talked about......however I was not really sure whether they exclusive or not. After the unplugging my O2 sensor bit.....I had about 5 degrees of timing retard at a certain throttle.....even after plugging the O2 sensor back in. I then ran a clear memory procedure to clear the codes, and once I did, the 5 degrees of timing retard went away. So...using that example I will pretty safely say that clearing the codes does mean resetting the ECU. I'd like to do a few more tests before I say this with 100% confidence......but I'm pretty sure.

Dave as for your situation. Those two sensors are probably dead and throwing out-of-whack signals to the ECU. So even if you reset it, they are still going to be there when check the codes.

The ECU does respond a little differently with codes in it....even if they are past codes. So it would be advantageous to get rid of them for good.
Josh

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Post by DLC »

Yeah, the CPV should probably be replaced...

I'm almost certain that the inhibitor has something to do with the start inhibitor, where the clutch has to be pressed in in order to be able to start the car. I obviously don't have that connected, and i'd have to look in an FSM to find out if it could be done.

As an addendum to my previous post, at no time with the two d-mode connectors plugged in did it ever flash regularly, but i don't think i drove around very long with both sets plugged in. When i unplugged the d-mode connectors after driving for a bit, the codes on the other connectors were still there, which is puzzling.

I'd like to be able to reset these myself, or not have to drive to SLC to have a friend do it.

Dave
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Post by Legacy777 »

The inhibitor has to do with the shift lock mechanism you had on your auto. The manual cars have a ignition/clutch switch that acts the same way. If you can get a switch and if it operates the same as the inhibitor, you can just stick the switch in, and be good to go.

Other option would be just to bridge the connector, and that way it should think everything is cool. Like I said....I'll look a little more closely when I get home.

The way D-Check mode works is that it runs the more active diagnositic......if it finds errors or problems. It won't ever blink steadily. So if both of those things are there, and causing problems, the computer won't clear them.
Josh

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Post by Legacy777 »

Book says on the CPV.

If you test it....it should read 36 ohms at 68 degree F

The inhibitor switch.

It looks like it should conduct when in neutral, and not conduct when in any other position.

The manual tranny's neutral switch is actually backwards. In neutral, 1M ohm min.......which should be an open circut. Any other position 0ohms

So it's possible that the ECU is expecting 0 ohms now that the MT/AT identifier has changed.

You should either be able to ground the pin for that lead or if it's connected....disconnect it.......Sorta depends on how it was setup when you did your tranny swap.
Josh

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Re: Can't reset ECU?

Post by Vubawoo »

bringing back a thread from the dead but I have a similiar concern.

ej22t auto. Bought the car used with this issue. Recently replaced items - speedo cable, starter, alternator 12v battery, oem cam and oem knock sensor. Maintenance items - Valve cover gasket, spark plugs, oil change/filter, timing belt and cam/crank seals.

When I have the black connectors connected I read 11, 13, 22. crank, cam and knock sensor. I repaired wiring to crank and cam (brittle and wires exposed or broken), also replaced cam and knock sensor (due to car dying or no start and cam sensor was aftermarket). Ohm out wiring for crank, cam and knock sensor and Im getting 0.5ohms and no changes when I wiggle wires Car runs fine and no issues. When trying to clear the codes with green connector cconnected during driving I get codes 22. Some times I get 22 and 51.

After driving I recheck codes and I get 11, 13, 22 still. I've try a couple different procedures I've read online to clear codes but none have worked. Im leaning towards possible ecu issue or some ground issue? But then again it seems to be driving fine.

any thoughts?
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Re: Can't reset ECU?

Post by wtdash »

HI,
I'd strongly suggest searching on here/online for microphone (or just mic) wire for the KS. Those wires are all suspect under the throttle body/intake manifold. FWIW, my 1st EJ22T had the same issue, seemed to run OK, but was in limp mode. Fixed the KS and had full boost (and ignition advance) - big improvement. 51 is likely just a phantom code related to the KS. Common for the main culprit to set off other, non-legit, codes.

Yes, could still be an ECU issue, and I'm not sure how to test for that possibility. And the EJ22T 5-speed and Autos use the same ECU from '91-'94.

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