Do O2 sensor errors affect performance / economy?

[JayOh]

Hello from Australia!

I have a 2004 4.0L that keeps getting P0135, P0141, P0155, P0161 errors. I keep clearing them with an OBD scanner, but within a few days they are back. Do these errors affect the PCM in any way? Would it cause poor economy? Often when it is cold started it smells like it is running rich and it rarely idles smoothly (but I don't have any other TJ experience to compare so maybe it's normal). I don't have any performance issues - it's quite responsive and there is no hesitation but it's a guzzler around town.

I have replaced the O2 sensors but no change. The complication here is the previous owner had to replace the PCM a number of years ago so he sourced a rebuilt unit from a company in Florida. The replacement unit is programmed for 4 sensors however mine only has 2. I purchased the 2 genuine Mopar items for an export emissions model from Rock Auto but they did not fix the errors. I've taken the Jeep to a local tuner shop that has HP Tuners and asked them to disable two of the sensors in the PCM programming - this worked for a few weeks but then the errors started coming back.

If the errors aren't causing the PCM to adjust air / fuel settings poorly or causing any excess consumption issues I can live with the CEL on the dash, but if the errors cause PCM issues and excess consumption then I'll need to look into a permanent fix.

Thanks!

 

[TheBoogieman]

@Wranglerfix to the rescue.

 

[Wranglerfix]

@JayOh-good day from Miami,

If the Pcm is failing it could throw those codes as well as poor fuel economy.

Who did you send the computer to? We have 10 different jeeps that we run computers in so our testing is much more thorough.

I was in Sydney and Port Douglas in 2008! You have a beautiful country mate!

 

[JayOh]

@Wranglerfix

I think they were called Solo Auto Electronics or Solo PCMS..

I'm not sure the PCM is failing, I think it was programmed to expect 4 sensors and after reading all the O2 sensor posts saying you have to use the NTK parts I'm wondering if I should try replacing the Mopar items with NTK to see if that stops the errors. If it works but only stops two of the errors I'd need to find a way to stop the errors on the other sensors that don't exist - possibly a purchase of HP Tuners gear or another visit to the tuning shop.

If that doesn't work the next step would probably be a conversation with you about replacing the PCM with one of your optimised PCMs given that mine is a 2004.

But the main question is - how does the PCM respond to those error codes, does it just flag the error or does it adjust the tuning in any way that would increase fuel consumption?