Hello,
I got a P-0420 code the other day for low catalytic converter efficiency. Could someone tell me how to test whether this is the catalytic converter or the oxygen sensor? The van has about 104,000 miles and wouldn't have expected the catalytic converter to go so early.

Also, does anyone know how to reach those bolts to change the catalytic converter? Looks very difficult to access.

Thanks!

 

The computor test's cat efficiency by comparing the upstream o2 to the downstream. If they both cycle at the same rate, it assumes cat failure.

You get to them from underneith with a long extension and a swivel socket.

 

Thanks Tizzy1!

Does anyone know how to test the oxygen sensors? Would be great if I can get away with just replacing the oxygen sensors. Replacing the catalytic converter does not look very fun.

 

I use my real scanner to read the values. you could also use a DVOM (electrial meter multi meter). P0420 is RARELY caused by a bad sensor. To replace the sensor you should get an Oxygen sensor socket available at any autoparts store. A simple test for a bad converter is to hit is with your hand (obviously when cold) if you hear a rattle it's definitely shot. replacing a cat is EASY if you have the proper tools, equipment and knowledge.

 

Thank you 92dak5,

I have AutoEnginuity. So, I will try to scan the real values. I like your idea about banging on the cat. So, I will give that a try too.

I've done a lot on cars but I just hate to get under the car to an extended period of time as I do not have a lift. I was thinking of trying to change the cat with the minivan on ramps. I have never had luck cutting exhaust pipes either.