OB99W

The info I'm looking at on TCU code 23 is for a '95, so it might not be totally applicable to your '92. It says that the symptom related to a code 23 would be lack of lock-up after the engine is warm. The procedure is to first check for the signal getting from the ECU to the TCU -- if it's not, check for wiring/connector problems between them. If the signal is getting to the TCU, the TCU itself is the problem. If the signal isn't getting out of the ECU (ECM), it says 'Conduct diagnostics for ECM's ignition system'. What exactly that means, I'm not sure, but both the crank and cam sensors play a part in determining ignition timing/advance. There's no indication that TCU code 23, by itself, would cause engine running problems.

Best of luck. Please let us know the eventual outcome.

Yes, see P0400 info in http://endwrench.com/images/pdfs/Emissions.pdf

I'm not sure how the ECU derives the engine rev signal that it sends to the TCU. The signal loss detected at the TCU could be due to a disconnect between the ECU and TCU, but given the engine running problems I'd be more inclined to think a sensor feeding the ECU is the problem. Are you sure that there are no stored codes in the ECU? Perhaps the CEL is out since the impact -- can you verify that it lights when the ignition is turned on, just to make sure the lamp works?

For code 42, check operation/adjustment of the throttle position sensor (TPS). Battery and brake light coming on typically indicates a charge problem, often due to a failing alternator. I'd deal with those two issues first and see if the trans problem persists afterward.

I want to expand on why it might be time for a dealer or sharp independent to look things over. Assuming that the problem's cause isn't obvious (since it hasn't been resolved easily via 'remote control'), good diagnostic skills could be key. For example, what if the timing belt has slipped a notch or two? It might explain starting and gas mileage issues, yet without some basic tests to rule that out, parts could keep being thrown at the problem. Sometimes it's worthwhile to bite the bullet, even given the chance that something 'simple' was missed and the result is 'overpaying'.

I sympathize -- your situation must be frustrating. If you aren't able to directly interact with the mechanic, then it's unfortunately possible that parts are being replaced without diagnosis. In your other thread concerning this problem, I asked if the fuel pressure regulator operation had been checked, but I didn't see a reply. It would have been useful to know both the fuel pressure and whether applied vacuum was properly controlling it. If the pressure was correct, it would obviously suggest looking elsewhere; if it was wrong, the vacuum (and associated hoses, etc.) would typically be checked before replacing the regulator. Probably the easiest way to reset the ECU is to disconnect a battery cable for a while -- 30 minutes will ensure the stored data will be erased and that the memory won't be corrupted (which sometimes happens with a shorter time). Of course, radio station presets and clock settings can be lost. When the cable is put back and the engine started, let the engine warm for about 10 minutes without touching the accelerator so that the ECU will 'relearn' proper idle conditions. Checking for intake vacuum leaks has been suggested. Such leaks could result in either a lean or rich mixture, and be the cause of starting and other problems. For example, any air that enters the intake beyond the airflow measuring device (either MAF or MAP) is an amount over what the ECU 'thinks' the engine is using, and insufficient fuel will be injected for the air volume, resulting in lean running. On the other hand, if a leak causes loss of vacuum to the fuel pressure regulator, the pressure can be too high. Considering the circumstances, it might be prudent to have the problem diagnosed by a dealer or independent shop very familiar with Subarus if you're unable to look things over yourself.

Did you check the regulator's operation before replacing it? If so, what was the fuel pressure? Have you tried resetting the ECU after parts replacement?

The DTC being referred to concerns an auto trans solenoid circuit fault -- it has nothing to do with the service brakes (the ones that stop the car). In http://www.ultimatesubaru.org/forum/showthread.php?t=96778 you said that the engine had been pulled. If the trans problem showed up right after the engine work, it's likely that the cause is either a damaged wire or improperly plugged in connector to the trans that happened during the engine repair. In that case, a careful visual inspection will likely be revealing.

The blown fuse would certainly explain lack of alternator field current. It could have happened when the wrong alt was wired in, which is why I asked about that. Congrats on getting it resolved.

Those two lights will come on when there's an alternator field circuit problem. Do a search in this forum on 'alternator field brake', which will turn up a few related threads with the explanation. Is this the car that got an incorrect alternator spliced in previously?

Does the car pull left or right at all when the problem occurs? If not, and the only obvious symptom is the need for substantially increased pedal effort, then it's still likely that there's a failure of brake vacuum boost. The effort goes up dramatically if a vacuum booster isn't working, since it can add a few hundred pounds of pressure to your leg power when it's operating correctly. The vacuum line check valve operation is even more important with a turbo than it is with a normally-aspirated engine, since intake manifold 'vacuum' is replaced by 'pressure' during turbo boost -- if the check valve doesn't close, the vacuum stored in the booster is immediately displaced. If the valve is 'sticky' and doesn't open when vacuum is present, there will be no brake boost even when there's sufficient intake vacuum (no turbo boost). In order to help determine what to concentrate on, you might 'T' a vacuum gauge in the line between the check valve and the booster, and see what it reads when the problem occurs. If it's okay, there could be a porting problem within the booster.

Okay, but I don't bury the needle very deeply into E territory before I chicken out. Now Nipper's going to be really annoyed.

I do run some Techron periodically, so that might explain my gauge's, umm, 'accuracy'... or not. More likely, just random luck.

Now who's showing off?

Nah -- showing off would be if I actually got anywhere near the 30 MPG.

You're forcing my hand. I wouldn't call mine 'accurate', but from E it takes nearly 14 gals to fill. However, it's very optimistically non-linear at the top end of the gauge, looking like I'm getting 30 MPG for the first 1/4 of the tank and then dropping like a rock for the rest of the way to compensate.

Nipper, if enough people reply to this thread, I suspect you're going to become annoyed. (I won't say what mine takes to fill from E until others chime in, but it certainly isn't 10 gals.)

Welcome to the forum. We could probably better advise you if we knew what specific fault is causing the CEL. The larger automotive parts stores (AutoZone, Advance, etc.) usually will read the OBD-II trouble code at no charge. If you have one nearby, get the code read and let us know what it is (the Pxxxx number, not the code definition, please).

Model and year, please. EDIT: Your profile lists '84 EJ Brat' and '98 imp obs' -- can we assume it's one of those?

Moisture in brake lines isn't good. However, even without the bleeding/flushing procedure that wtdash used, it's very unlikely that there could be enough water in the brake hydraulic lines to freeze, at least under normal circumstances with systems running glycol-based fluid. Those fluids are hygroscopic, and moisture will disperse throughout the fluid, rather than form pockets that could solidify. The chances are much greater that moisture-contaminated fluid would boil under hard usage (and/or cause brake system corrosion) long before it could freeze.

Certainly a possible cause/effect relationship on sufficiently cold days. You're welcome, I hope that's it.

See this thread: http://www.ultimatesubaru.org/forum/showthread.php?t=93492

Sounds like it might be a problem related to the vacuum booster. What's the temperature on the days you've had the problem?

That's normal behavior, especially under weather conditions this time of year where you're located.