I installed a Bosal exhaust on the '98 Max. It's a DD, gently driven car, so I went OEMish.

After a couple hundred miles it threw an P0138 O2 code along with the ghost 0325.

The Bosal system has that funky post cat O2 hump pipe in a slightly different arrangement than the original exhaust. It comes in at a 90 degree, rather than being slightly outbound on the hump like the original exhaust. I'm thinking that perhaps it's sniffing more and throwing the code? Another thought is that maybe I damaged the o2 sensor in removal - it did not want to come out and I had to use the impact wrench on it. I was gentle, but it is an impact wrench.

Thoughts? Should I try an extender on the O2? Or should I put in a new sensor? My time with this car is a little limited, so I need to hit this fairly soon and know it's working. Maybe do both for good luck :-) ?

PS. How long do the O2 sensors usually last on these cars?

 

I've seen people use spark plug foulers in places of the o2 sensor bung on the exhaust, then bolt the o2 sensor to the plug fouler and get rid of the codes. Personally unless you have emissions i wouldn't stress. But I'd try new o2 there like 19 bucks new.

 

We do have testing here, so I need to get the code off. The bosal exhaust puts the sensor in an exposed location a little too low anyway, so a 90 degree extender might solve both issues. But, the sensor has 114k miles... I suppose it's due for replacement soon anyway. I may try both items... :-)