Was wondering if anyone had any ideas. CEL came on last week in a rain storm and code read cat convertor low efficency. Had it reset and it was fine for about 5 days. Yesterday in a rain storm it came back on. What is the likely hood of it being either 1 or both of the O2 sensors and setting off this code? The MPG have dropped a little (from 28 down to 23) over the past week. I'm going to try the "rubber mallot tap" on the catalytic convertors this afternoon and see if I hear anything loose in there.

Rubber mallot test will just tell you if the cat is rusted out. How many miles are on the car ? A drop in gas milage can be bad o2 sensors. I think the two sensors check the cat performance, before and after.

 

With the drop in gas milage, are you also feeling like the car has lost some performance. Depending upon the milage I would suspect the O2 sensor/s .

 

nipper

It's a 1995 Legacy LS with 158,000 miles on it. There may be a little drop in performance going up a steep hill, but not much otherwise that's really noticable.

 

 

Would taking off the converters and doing a visual be more effective at telling. Probably there isin't a real test for weather or not the converters are going other than the CEL though huh?

 

My concern is having to pay to replace one of the converters that may not have anything wrong with it. Is it worth doing the O2 sensors first and then the rear convertor and then the front? (Prices around here are around $170 for the rear and $195 for front, that's the low end)

I'd just replace the front o2 sensor, and leave it at that.

Was wondering if anyone had any ideas. CEL came on last week in a rain storm and code read cat convertor low efficency. Had it reset and it was fine for about 5 days. Yesterday in a rain storm it came back on. What is the likely hood of it being either 1 or both of the O2 sensors and setting off this code? The MPG have dropped a little (from 28 down to 23) over the past week. I'm going to try the "rubber mallot tap" on the catalytic convertors this afternoon and see if I hear anything loose in there.

 

Rain is the common factor...I'd check for a loose connection, or corroded connection on the o2 sensors.

Replace the O2 sensor first. The two O2 sensors once up to cnuff will tell you if the cat is working. Cat is not a cheap part to replace, so do the simple and cheap stuff first.

 

 

 

nipper

What year is your car? Subaru has 8 years or 80,000 mile warranty on there cats.

 

 

Was wondering if anyone had any ideas. CEL came on last week in a rain storm and code read cat convertor low efficency. Had it reset and it was fine for about 5 days. Yesterday in a rain storm it came back on. What is the likely hood of it being either 1 or both of the O2 sensors and setting off this code? The MPG have dropped a little (from 28 down to 23) over the past week. I'm going to try the "rubber mallot tap" on the catalytic convertors this afternoon and see if I hear anything loose in there.

How about getting a good obd2 interface for under $100 and learning how to use. Probably better than swaping good parts.

It is possible that your cat is marginal and cold water cooled it down sufficiently for efficiency to drop below treshhold. It is also possible that water temporalily fouled the sensors, wires, connections, etc. I past, I replaced a lot of good parts because of my poor traubleshooting skills. Many marginal mechanics operate this way, too. In retrospect, not worth the cost and effort.

Was wondering if anyone had any ideas. CEL came on last week in a rain storm and code read cat convertor low efficency. Had it reset and it was fine for about 5 days. Yesterday in a rain storm it came back on. What is the likely hood of it being either 1 or both of the O2 sensors and setting off this code? The MPG have dropped a little (from 28 down to 23) over the past week. I'm going to try the "rubber mallot tap" on the catalytic convertors this afternoon and see if I hear anything loose in there.

 

What is the year and model of your car? Converter codes are usually correct; unless you have an exhaust leak. Oxygen sensors do not nomally cause converter codes. Yet an air fuel ratio sensor can go bad and damage a converter; thus causing converter codes. I've seen many that come in for converter codes then come back later with codes stored for an air fuel ratio sensor failing.

Does anyone know if an OBD II scanner can tell which of the catalytic converters is faulty or failing? I'm going to pick up a scanner tomorrow. Does each converter have it's own code or will it still be a luck of the draw? Also, going to check out the sensor connections. Could this have anything to do with the slight drop in MPG? I don't appear to have an exhaust leak, but will look again tomorrow. If there were a leak, would that still give me a cat code? Will replacing/repairing it correct the problem?

 

 

Still hate to replace such an expensive part if I don't have to.

 

1995 Legacy LS wagon, 158,000 miles

Does anyone know if an OBD II scanner can tell which of the catalytic converters is faulty or failing?

No, it wont. You can only look at the tracings from front and rear O2 sensors and compare. If identical with a hot cat (after a nice drive), it's shot (poisoned).

Now, you have a 1995. OBD2 came in 1996 for most cars. You have to check if your car uses OBD1 or 2. Those are totally different standards.