Catalytic Converter & all 4 O2 Sensors replaced - CEL now says all 4 02 Sensors are bad

[ggeorgia]

Hi guys.

About a month ago the CEL lit up on my '04 Tahoe. I went to O'Reilly to get the code checked and they came back with P0420. Since the truck has 181k miles on it, I figured it was time to replace the catalytic converter as well as the 4 oxygen sensors.

I replaced the OEM catalytic converter with Magnaflow 93419. The OEM oxygen sensors (wiring looked pretty chewed up I might add) were replaced with 4 Bosch 15284 sensors. I didn't expect to have an issue using these aftermarket sensors since the reviews of others with the same make/model truck reported nothing but success. After installing all of the new hardware, the CEL was still on after 100 miles so I reset the computer by disconnecting the battery and reconnecting it.

Today -- a week after installing-- the CEL lit up. I went to AutoZone to have them scan for the codes and am getting: P0135, 0141, P0135, P0141 -- basically it's saying that all 4 oxygen sensors are bad after I replaced them with new ones. Any ideas on what might be wrong?? I checked the fuses for the oxygen sensors in the underhood fusebox they looked ok -- even swapped them with other compatible fuses to make sure this isn't the problem.

 

[mizzouguy]

http://troubleshootmyvehicle.com/gm/4.8L-5.3L-6.0L/upstream-oxygen-sensor-diagnostic-1

Here's a diagnostic procedure for it. Basically you check for power and ground on the vehicle connector to each sensor you are having issues with. If you've got power and ground, you check resistance. Bosch are cheap. It's possible you got 2 bad ones if you already verified the fuse or fuses powering the heater circuits is/are good. P0135 is for bank 1 sensor 1 (drivers side upstream) and p0141 is bank 1 sensor 2 (drivers side downstream) and then they repeat, so you are only showing issues with the 2 on the drivers side.

 

[ggeorgia]

I got 2 of the Bosch sensors from eBay after buying the first 2 from RockAuto since they were cheaper. Now that I think about it, I believe those are the two on the driver's side. Lesson learned -- you get what you pay for. Thanks for the help!!