himile99

All fixed now. That problem was 18 years in the making. The wiring harness was pinched under the right rear seat belt tensioner. Ready for the next 300K.

I did in fact save it to my computer, gotta love free stuff! Test light worked like a charm too! It finally went off when I unplugged the rear harness at the right kick panel. The offending wire splits five ways so I started snipping them, of course, the last one I picked was the culprit! So I've got a little extra soldering and heat shrinking to do. I figure I better pull that section of harness out to see if there is any further damage. Not going to finish it today, but I feel much better knowing the mystery has been solved. Thanks for the help!

I'll be rigging up a test light later, thanks for the link to the manual!

Dang, this isn't going too well! Bulbs and sockets all looked good. Have disconnected the hatch, both tail lights, trailer harness, and both headlights. Things are still popping. I replaced the tail/clearance fuse with a 20A circuit breaker (don't shoot me, it's all I had) and the main with a 25A fuse (until it gave up). The right front clearance light lit both filaments until I fiddled with the ground contact, afterword it only lit the clearance filament but the breaker still pops. Another clue might be that the sub-fan 2 fuse was blown, I don't know for how long though, when I replaced it, the fan worked fine. This is one of the few vehicles I don't have a factory service manual for, anyone had any luck with downloads or CDROMS from Ebay?

Both those suggestions make sense, and the hatch wiring was already a thought. Also, if the Haynes manual diagram is correct, the tail light fuse is after the combination switch, so that shouldn't be the problem. I'll start checking things out a bit later...

After 301K miles, my amazingly trouble-free wagon has started popping the fuse for the tail light circuit. None of manuals I have is very helpful. Does anyone know of a weak spot in the system to zero in on? Is there a connector somewhere so the front or rear lights can be disconnected to narrow this down?

Update time... Fairtax4me - That's a plausible theory, since I don't know what the old ECU is from, you might be right. Got around to reading the TSB you posted, it looks like I should have passed without doing anything. I doubt it if the staff at the instant oil change place would've known what to do. I cleaned everything related to the EGR system from the throttle body to the head port, wow, what a mess! Turns out my old EGR valve wasn't bad, my lips leak. I got a new vacuum pump and it's fine. I picked up an extra valve and and transducer from the u pull it for $4.50, just in case... Glad I didn't spend the $150 that NAPA wants for the valve! I cleared the P0400, which hasn't come back. After clearing the code and before starting the car, 3 of the monitors were "ready". Strange, but thanks for the head start! After a good amount of driving, I get the feeling that EVAP may never go ready, just the same way that catalyst never went ready with the old ECU. It'll pass like that, so I don't care. When I have the time, I'm going to try the old ECU, and other new one, just to see what they do.

Good news! The new ECU is totally right! Not only is the EGR valve diaphragm leaking, but when I open it manually at an idle, nothing happens, so the passages are clogged too. I never knew about it because my scanner doesn't do pending codes, and given that the old ECU had memory problems, it didn't pick up on the problem for the 2 consecutive starts needed to throw the code.

grossgary- I agree with you, except when when it comes down to the possibility of having New York State telling me to park my car permanently. I was just trying to avoid spending hard earned cash on the wrong parts. I actually have a long history of building Frankenstuff. ivansimports- You were only half right. So here's the update: Put in one of the ECUs this morning, it fired right up, and even felt more lively (probably has a different spark/fuel map). Some, but not all, of the monitors went ready. The nice thing is they stayed that way after cycling the key. As of my trip home, all monitors except EVAP have set and stayed. So it appears the ECU was faulty. Here's where ivan comes in: As soon as it reached operating temperature on the second start-up, the CEL came on, P0400. Frankly, I'm not too surprised about it. Or worried. At 269,000 miles, either the diaphragm is shot, or something is plugged. No big deal,I can work with that. The funny thing is that the old ECU didn't throw the code, it had no trouble throwing others. A P0446 a month and half ago lead me to the USMB, which lead me to the mouse-chewed and corroded vent solenoid wire right over the fuel pump. If that hadn't happened, I wouldn't have been watching my monitors to begin with, so here I am. I hope this thread can get someone else out a jam, as this doesn't appear to be a common problem.

Well, I'm gonna find out tomorrow, yanked 2 at the U Pull It. $20 each, how could I go wrong! I'll give you the auto/manual interchangeability, but a previous post states the '97's pins are different, and Hollander says that the '99's are unique, with a difference for 49 state and California. I believe the numbers do have meaning, otherwise why would they change? I also believe the AD70B was the final update, since it appears to be the most common. Hopefully, I'll only have to make one more post...

I was wondering that myself... Considering the car was (and still is!) a real cream puff, I'm hoping it's just a flaw in the ECU.

I actually googled the name written in paint pen. It turned up a salvage yard in Scranton, PA, the same city I bought the car in. So at least that makes sense. Spent an hour looking around ebay and came up with an ECU from a 99 legacy GT, 49 state, MT, build date 7/98 (same as my OB), code AD67A. Code on my ECU is AC910. I can't see why a GT would be any different. At 110 bucks, I'm keeping it in mind. Heading for the U-Pull It in the morning. Got my fingers crossed....

Relegated myself to finding a new ECU, so I went to grab the numbers off it. Voila, junkyard pen on it! So it's not original after all. I can't be sure it's the right one. Anyone know the correct ECU numbers for a 49 state, 2.5L, MT? Cougar, I know it's an easy fix, but finding the right one, in working condition, for under an arm and leg is going to be the hard part.

Cougar, that is soooo not the answer I wanted to hear...

Here's a quick update. Swapped out the front O2 sensor for one with a lot less miles this afternoon. Fired it up and HO2 set quickly as normal. Got called in to work and managed to get there without setting the O2 monitor, but the catalyst had set! I figure I didn't open the throttle enough. The exhaust is solid before the front cat, might be a small leak before the second cat, but I didn't have a helper today. Since both O2 sensors are in the front cat, it shouldn't affect anything. Everything set on the way home, until I turned the key off... same 3 monitors not ready...grrr!