After some research it seems that code refers to the post cat o2 sensors giving abnormal readings.

The message said "BANK 1(5)"

How do I know which post cat sensor is giving abnormal readings? I would like to switch the sensors around to see if its the sensor or the cat but I don't know how the ECU will tell me which sensor it is.

The truck has over 261,000 Miles on it and runs great. My guess would be the Cat is the issue.

 

bank one is drivers side exhaust, and referred to when both sides come together into one. bank 2 is pass. side until it merges with bank 1. if it's dual exh., then it remains bank 2. sensor(s) 1 are before cat, sensor(s) 2 are after cat.

 

So the drivers side manifold and the sensor after the cat is bank 1?

 

yes. bank 1 sensor one is pre cat. bank 1 sensor 2 is post cat.

 

So I picked up a Actron code scanner cp9580.

I looked at the real time date while the engine was running and there are three sensors which look to be the o2 sensors

Recorded Values while at engine idle 680-720rpm for about 31 seconds. Values seem to jump all over the place and never stay in a steady range.


Bank 1 Up Stream Sensor O2s11 (min value: .014v max value: .910v)
Bank 1 Down Stream Sensor O2s13 (min value: .190v max value: .755v)

Bank 2 Up Stream Sensor O2s21 (min value: .075v max value: .915v)

Error was originally for bank 1 and my guess is both up stream sensors will vary a lot in value since they are before the cats but the one after the cat should be fairly steady? If its a problem with the down stream sensor's values than I believe that is a different sensor than upstream so I wouldn't be able to swap that around. At 261,000 miles I wouldn't mind replacing the CAT but what do you all think?


I read on the forum somewhere the o2 sensors values shouldn't jump around and if they do then the cat could be bad?

 

The o2 sensors are supposed to move constantly. 99.9% of the time po420 is a bad cat

 

Ok, I'll just bite the bullet and get a new cat and pipe assembly. Thanks