I have a 98 A4, 2.8. quatto. The check engine light came on. Code PO432. Brought it to monroe muffler. Replaced right side cat and after cat O2 senser. After about 60 miles the code came back. Check engine light on. Went back to monroe. They rescaned it, everything looked good it time the light came on and real time. Cleared code and it came back again after 60 miles. Is there some thing we are missing?

 

I'm not sure what model years are affected but some of our cars have the cat efficiency tolerances set too strict in the ECU. Dealership can recode the ECU to accept a looser tolerance. that should fix you problem

-it is possible I have no idea what I'm talking about

 

P0432 is "Main Catalyst Efficiency Below Threshold (Bank 2)". Bank 2 is the side of the engine that doesn't contain the #1 cylinder. Looking at the front of the engine, cylinders 1-3 are on the left side of the engine and cylinders 4-6 are on the right side of the engine. However, right and left are usually used as if you were sitting in the driver's seat. So if you changed the right cat and O2 sensor (as if you were sitting in the driver's seat) then you would have changed the cat and sensor for bank 1. If you haven't already, you should be looking at the driver's side as being the culprit. Just trying to clear things up.

 

Jeckel is correct. Bank 2 is on the drivers side of the vehicle. Go back to those morons , get your money & your old cat back.
Replace the cat with a factory one , install 2 new o/2 sensors reset faults & be done with it.
Aftermarket cats are crap & only a temporary fix at best!

 

i have been a mechanic for 14 years, and i agree with M5S5 aftermarket catalytic converters are complete crap. they may be cheaper but you do get what you pay for and there is a reason that they are hundreds of dollars less. they go lite one some compounds that are used in the chemical reaction and completely skip others. i try to sell my customers only OE converters and if they wont buy one and want an aftermarket i make it very clear what the outcome of that could be.

 

Thanks,

They replaced the wrong side. But, what I don't understand is when looking at real time data all 4 O2 sensors look good. When they went to look back at the time the light came on, all was good also. Before sensors were reading around -0.5 to 1 and the after ones were both reading 99.2.

 

What scanner were they using? If they were using somthing different than a VagCom or a 5052 than i would not rely on what they are reading.

 

that 99.2 number is a percentage value and is totally useless all you want to look at are voltage readings. the upstream sensors should change from around 0.2V ish to around 1.0V and the down stream sensor should be a mostly steady reading if it is changing at the same rate as the upstream then the converter has failed. scantools show a lot of data in the datastream but some of what they show you has no tangible diagnostic value.

 

Where can I check the voltages? I know the 4 sensor plugs are on the right side on the fire wall.

 

Either with a scantool or with a labscope a volt meter doesn't sample at a fast enough rate, even the scantool is slow but if it has graphing capibility it will do the job. I usually use a scantool when I'm diagnosing a converter issue.