ABS Light on = No Check Engine Light?

[RallyKeith]

I've got a 96 Legacy GT Wagon 4EAT that has had the Check Engine Light on for a legitimately bad front Catalytic convertor. A few months ago I broke one of the ABS tone rings in the front trying to get a rotor off. I don't drive this ca very often, but yesterday I drove it and noticed that while my ABS light comes on a soon as I hit the brakes for the first time, my check engine light is no longer on. Is that normal? Before someone asks, the bulb for the light is still good. The light comes on and goes out when I first start the car.

 

Keith

[j2coe]

I think that the ABS system has its own controller and wouldn't trigger the check engine light since the systems are diagnostically unrelated. I'm admitedly not as versed in the newer models and am still larning things like this. I had a chevy lumina that had a common ground for the AC, fan and some unrelated trouble light so periodically the light would go on and the fan and AC would fail to work. shut off the car, start it again- light was out everything worked. weirdest thing. had to take it to the dealer when it was doing it for them to believe me.

[Strakes]

CEL, and ABS lights are not related. I bet that the ABS light is because of the broken tone ring. The CEL is probably because something else. What was the CEL code?

 

I got a CEL and it went on and off a few times over several months until I got a steady CEL that wouldn't go away. The front 02 sensor was the culprit...the code was P0420: catalyst sytem efficiency below threshold bank 1. The Autozone dude, who read the code, immediately declared it the convertor, but wise usmb people told me that the cats rarely fail, and the front 02 sensor should solve the problem. It did.

 

Also, the CEL will disappear after the condition isn't repeated for iirc 3 times. My pesky 02 sensor failed slowly/intermittantly over time, hence the CEL going away and coming back.

[RallyKeith]

CEL, and ABS lights are not related. I bet that the ABS light is because of the broken tone ring. The CEL is probably because something else. What was the CEL code?

 

I got a CEL and it went on and off a few times over several months until I got a steady CEL that wouldn't go away. The front 02 sensor was the culprit...the code was P0420: catalyst sytem efficiency below threshold bank 1. The Autozone dude, who read the code, immediately declared it the convertor, but wise usmb people told me that the cats rarely fail, and the front 02 sensor should solve the problem. It did.

 

Also, the CEL will disappear after the condition isn't repeated for iirc 3 times. My pesky 02 sensor failed slowly/intermittantly over time, hence the CEL going away and coming back.

 

Mine had been throwing the P0420 code for literally two years, but I know I have a partially clogged front cat. You can actually hear it wistle above 3000RPM and also at full throttle. I know the ABS light is on because of the broken tone ring. I just don't understand why my CEL is no longer on when I haven't touched anything in the exhaust.

[nipper]

ABS light is the broken tone ring.

 

How do you know the converter is truly bad and its not a lazy O2 sensor?

 

 

nipper

[RallyKeith]

ABS light is the broken tone ring.

 

How do you know the converter is truly bad and its not a lazy O2 sensor?

 

 

nipper

 

Nip, did you read my last reply at all? (I'm just teasing you)

 

First off:

I know the ABS light is on because of the broken tone ring.

 

Second off:

Mine had been throwing the P0420 code for literally two years, but I know I have a partially clogged front cat. You can actually hear it wistle above 3000RPM and also at full throttle.

 

Here's my thinking on the Cat/O2 Sensor. Please comment:

If it's not the cat, then something else is causing my exhaust to wistle, and it's only gotten worse as time goes on. The car has just shy of 200k miles so I'm not going to completely rule out the O2 sensor, but I've also owned several other +200k mile subarus that never had a bad O2 sensor so to me it's a toss up in that respect.

 

Also, this car had a motor in it that "burned" 1 quart of oil every 150 miles due to improper valve guide seal installation. That motor was in for about 3500 miles so it went through 24 quarts of oil. Not all of that oil gets burned in the engine, some of it gets burned up in the cat which is why I believe the cat may have over heated at some point and started to melt causing the whistle.

 

Keith

[nipper]

Yes i did read silly.

 

Cats can handle oil consumption surprisingly well. The O2 sensors don't like though. What cats can't handle is ra gasoline. When you burn oil it all does get burned (for arguments sake).

 

If the light is off, see what happens. If you Bang the cat with your hand and it doesnt rattle (when its cold) then your cat is fine.

 

It's possible the O2 sensor has cleared itself up. On a sooby an O2 sensor can go bad at any time over 80,000 miles, but more typically its in the 180,000 range.

 

nipper

[OB99W]

Another possibility to consider -- an exhaust leak can both cause a whistle and set P0420.

[RallyKeith]

Another possibility to consider -- an exhaust leak can both cause a whistle and set P0420.

 

I hadn't considered an exhaust leak since it passes inspection, but they check for leaks at idle so it might be a small enough leak to not be detected at idle.

 

Car goes for inspection next week so I'll be curious to see if the mechanic finds anything.

 

Keith