Is it possible to repair an (obd2) car that has emissions monitors that show as incomplete?

Both of my dads cars (1996 Legacy 2.2 and 95 Neon) have this problem, and its far beyond my ability to understand. I am not sure if its something that could possibly be fixed, or does it mean they are both going to be part of California's push to get all cars over 20 years old off the road as soon as possible?

On the neon, it has a code for high coolant temperature sensor circuit voltage, and all of the emissions monitors show incomplete. The gauge cluster also works only intermittently, although I am not sure that is related, because I think the decomposing dash plastic doesn't hold the gauge cluster in the right place for the pins to make contact anymore.

The Subaru has only 3 incomplete emissions monitors, the upstream oxygen sensor, downstream oxygen sensor heater and the catalytic converter.

Does anyone have any ideas of what could be wrong with either one? Or is it time to give up. If anyone has any ideas that would be awesome, its just kinda frustrating to have to try to fix something in not smart enough to understand.

The cars need to be driven more.

Really. The message that the monitors are incomplete means you need to find the part of the cycle that you can replicate that will run the monitors.

The Subie- probably need to do 40-55mph in a slow ramp or so. Those usually run on the "big hill" of the cycle. Which is an acceleration to 35, hold for 20 seconds, slow to 25, and then speed up to 55 for about a min. Then slow to a stop.

If you look up what the FTP cycle is, all of the monitors are supposed to be run within two full cycles of that.

That's interesting, the neon actually lists the test conditions in the fsm, but the Subaru doesn't. That does sound very possible though, the neon hasn't been driven much in a long time, and the Subaru has been driven daily but only a short distance at a time.

The cycle is a start from 70F, driving for 7 miles (in just under 1400 seconds), shut down, 10 min wait, and start and drive for 3 miles (505 seconds)- a total of 10 miles or so. A car that doesn't drive much may clear the codes, and a car that drives just a little may never finish all the tests.

What's hard about both cars- they are the first year for OBD, so we were all learning about how to make it work.

Interesting, I will have to try that. The Subaru has always had issues with the catalytic converter test failing and setting a code, and it has been driven pretty much everyday at least 40 miles, but the neon hasn't made any long trips in quite a while. How new does a car have to be before the emissions systems were figured out well enough? As nice as my diesel Mercedes has been with no emissions tests at all, I am selling it for other reasons but I would rather get something that isn't too big a hassle to pass the emissions tests here.

Do either have a check engine light? If not then they just need to be driven. If they do and the CEL codes are related to coolant temp sensor or 02 sensor the tests will show incomplete until the CEL is resolved.

The neon has a code for the coolant temp sensor circuit, but idk what it means. If the gauge has to be working to clear the code, that's a pretty big problem because I think the dash will have to be replaced. The Subaru doesn't have any codes, and the check engine light isn't on, but the harbor freight scan tool says it is (maybe the bulb is burned out, but if there are no codes why would it be on?).

The dash won't have to be replaced on the Neon. Intermittent gauges are a well-documented fix over at neons.org. Start with the grounds everywhere; if that doesn't cure it, it may need to be pulled out and resoldered. But it won't need to be replaced.

I never did get the Depressive Miata (1996) to clear all the incomplete monitors, despite having a bunch of different driving profiles to try.

On the neon I mean the actual plastic structure of the dashboard, not the gauge cluster, because I already changed it once and it still doesn't work, and I found out that pushing up on the bottom will make the gauges function again.

The problem (why I am even worried about this to begin with), is that if there is more than one incomplete monitor the car won't be able to pass emissions and be registered anymore.

AFAIK on OBDII cars if the computer isn't getting a correct reading from the coolant temp and both O2 sensors the monitors will never complete. The computer is looking for the engine to be in a certain temperature range and uses the O2 readings to determine if the converter is functioning properly under certain conditions. I think once you fix the CEL on the neon the monitors will complete. There are two sensors, one for the computer and one for the gauge so the gauge not functioning shouldn't have anything to do with it. I'd try a new coolant temp sensor. It should be located near the thermostat housing with a two wire pigtail. The smaller sensor with one wire is for the gauge.

The Neon dash needs the pins resoldered on the circuit board. The reason it didn't change when you put a used one in, is that none of them work until you resolder the pins.

The coolant temp code doesn't have anything to do with the dash. It needs a sensor, or a wire connector, or a broken wire repaired, or a new ecu.

I am still really not sure what to do :(, it sounds like the Neon needs a new wiring harness then (for a 19 year old car that had terrible wiring harness problems since when they were new), and for the Subaru I need to blindly throw $1k in parts at it and hope something fixes it, then give up and sell it to the state to scrap it when it still has the exact same problem. I hate new cars, and I hate California emissions laws...

In reply to Travis_K:

I understand the despair, but I really don't think the Neon is that hard a fix. Start with replacing the coolant temp sensor that is throwing the code. The dash resolder is not that hard. Those are the obvious sources of trouble, and fixing them may fix the OBDII issues.

Or you could buy a coolant temp sensor for the neon, clear the codes and drive it for a few days. Then drive the subie for a few days and see if the monitors complete.

Not the end of the world unless you are looking for a reason to scrap them.

I can try a new coolant temp sensor on the neon and see what happens, I guess there is no way to tell without fixing the gauge cluster first, but a used sensor would be cheap. Its already on its second engine harness though, so failed wiring seems a lot more likely. I have been driving the Subaru 20 miles back and forth to work everyday for the last couple months and the monitors still haven't completed, so its possible that it just hasn't been driven in the right conditions, but more likely that there is a problem somewhere. We have put 300k miles on it since we got it at 150k and it has had pretty much constant oxygen sensor or catalyst efficiency codes that whole time, and even replacing the cat once and the oxygen sensors many times it never really fixed it.

Neither car has the original engine, the one in the neon has ~75k, and the one in the Subaru has about 250k, but I have a 98k mile engine and 160k mile transmission for the Subaru that I got for less than $300 for both, and since the rest of the car is still fine, I do want to keep using it longer if it can be repaired enough to pass emissions again.

I would really like to fix them, I am just very bad at figuring out new things, if its something that I have a pretty good idea what needs to be done before I start (like a front suspension rebuild, timing belt, clutch, etc) that's fine, but trying to diagnose and fix weird electrical problems or stuff like this seems impossible.

In reply to Travis_K:

Here's a video on the Dash repair for the Neon:

https://www.youtube.com/watch?v=CtwnsPmkX1M

A cheap soldering iron from Radio Shack or Fry's, some solder and a little practice. Get to it.

Coolant sensor just unscrews (though you may want to drain the coolant a bit first to avoid getting it all over the place) and if that doesn't fix it, then look at the connector or wiring and either splice in a new connector (Its a pretty standard GM weatherpack connector, take the old sensor in to a decent auto parts store to find the proper connector) or repair the broken wire(s) by carefully unwrapping the harness until you either find a break to fix ot uncover the entire wire to the firewall and you can splice in a new pair of wires from there. Just pretty standard old car repair stuff really.

As for the Subaru, yeah the catalytic converter for Cali cars won't be cheap. Oxygen sensors shouldn't be too bad and you might find them all cheaply enough on RockAuto to get by long enough to sell the car.

BTW, it isn't just Cali rules, I'd have to deal with the same thing up in here in Portland, Oregon or even in metro areas of Washington. My 79 924, 88 944 Turbo, 94 740iL all passed tailpipe emissions tests and the Porsche's aren't anywhere near to stock, but all of the EFI sensors were working properly (even if the BMW is showing other errors on the dash). Wife's 01 Highlander passed emissions without issue as well. If you want to avoid the emissions testing, then move to an area of Cali that doesn't require emissions testing (they do exist). Otherwise do as the rest of us do, roll up your sleeves and fix the problems.

Just check with the scanner to see if the cel comes back on after the new sensor. On the subie try and borrow a scanner with live data capabilities so you can see what the O2 sensors are reading.

In reply to Travis_K:

Think of electrical circuits as plumbing if that helps. The electrons (or water) needs to be flowing in the proper directions in order for the system to work. If it isn't then you've got a problem with the circuit someplace (a broken or blocked pipe would stop the water flowing, just like a broken wire would stop the electrons from flowing). Isolate the problematic circuit at both the start and the end and verify continuity with a continuity tester. Do this for each circuit and you'll can eliminate that circuit as a problem and move to the next piece in the system.

Coolant sensors can be tested using a thermometer, a DVM and a pot of boiling water assuming you know the resistance to temp conversion, which has been covered by the MegaSquirt conversion folks you can verify if the sensor is working properly:

http://forums.neons.org/viewtopic.php?t=297158

moparman76_69 wrote: Just check with the scanner to see if the cel comes back on after the new sensor. On the subie try and borrow a scanner with live data capabilities so you can see what the O2 sensors are reading.

this. You don't even need to put the sensor in the engine.

The code is a wiring code problem- be it a wire, a pin, or the sensor. The circuit is open somewhere. I would mention- it's probably between the sensor and the computer- if it were on the other side of the sensor, it would trigger multiple codes, as many sensors used the same source voltage as a reference. If that was bad, lots of stuff would be bad. So it's somewhere in the direct link between the engine coolant temp and the computer.

As for the subie- it's not broken.

Let me say that again- it's NOT BROKEN. At least it does not say that it is. Throwing parts at it will not make it run the monitor all of a sudden. See if there's a subie board that explains the driving range that runs that test.

It's not telling you it's broken, it's telling you that it has not been able to finish the test, yet. Very very different messages.

The Neon is telling you it's broken. Which is somewhere in the wire between the engine temp sensor and the ECU- which is probalby a very different sensor than the one the broken dash uses.

CA resident here, I was struggling with my Saturn, replaced the cat (it was bad) with a CA legal magnaflow and the o2 sensors with Denso quality replacements. Drove it to work (16miles/30min each way) and a trip to San Diego and back (3hrs each way) it was still showing "not ready," followed the GM "readiness monitor cycle" procedure more than once to no avail.

Digging online somewhere someone mentioned engine coolant temperature sensor and so I replaced that and once I got it up to temp, I scanned it with my code reader and sure enough it showed ready. No fancy drive cycle with x min/miles @ x rpm or mph or anything.

So in my case it had to do with the engine not being at the correct temp due to a faulty sensor to trigger the readiness monitors. No CEL or indication that it wasn't happy other than the "not ready" status and the temp gauge reading being slightly off.

And in regards to your Neon, I tend to agree with Alfa, the dash just displays the error, very unlikely it's the cause. You can use a scanner to see what the real issue is but it still may fail smog visual if the CEL isn't displaying/working correctly on the dash.

So, I had totally forgotten about this, but the engine in the Subaru is actually the second replacement with a junkyard long block.

The cat was replaced at about 280k with an aftermarket one, because we took it to the dealer (because it kept setting a catalytic converter effiency code) they said it was $1600 for the factory one, so it got a $600 one instead. I think now that might have been a big mistake, but I didn't know at the time.

After about 6 months the cat code was back again, then not long after that we decided to replace the engine because it was getting tired and burning a lot of oil. As soon as we drove it with the new engine, the cat code never came back. Unfortunately, the new engine got ruined due to the factory torque spec on the crank pulley being too low, and the only replacement we could find had higher mileage and the code came right back again. I had forgotten about lain, and it might explain why the test won't run, but the only reason the check engine light is off now is that we put a spacer in with the downstream oxygen sensor to make it read different enough to stop it from setting the code.

Is it burning oil?

Were the sensors swapped with the engine swaps?

Not a lot, but it may be enough. I guess I could swap the other engine in and see what happens, I am not really sure what else to do.

Really high end OBDII scanners can sometimes force readiness on the monitors, depending on the scanner\car