P0135 and P0155 - 02 Sensor Heater Circuit Malfunction Solved Finally

[Scrambler62]

I have a 2003 Wrangler Sport 4.0 5 speed
For the past year or more I have been chasing code P0135 and P0155 - 02 Sensor Heater Circuit Malfunction (Bank I Sensor 1, Bank 2 Sensor 1)
Replaced O2 sensors multiple times, checked wiring everything spot on.

The fix Wrong Thermostat. I replaced radiator and thermostat when I first got jeep but I put in 180 degree thermostat.
The factory spec is 195
Computer is programed for engine to heat to above 195 in certain set time, if it doesn't it throws code.

Engine idles better, shifts smoother, no cel over 3 weeks, now running at 207

Check thermostat for correct operation and heat range if you experience same.

Hope this is helps, Best

 

[greg92jeepxj]

Thank you for your post and for sharing your success with the forum. This will no doubt serve very informative to show how proper diagnostics is performed. Too often is it perceived that because a DTC is set that a part must be changed. You have proven that there was a leading cause that ultimately resulting in a knee jerk reaction of the engine management system to attempt to richen the fuel system to lower combustion temperature and pressure by using a richer mixture to cool the cylinders and reduce spark knock. You have successfully looked past the trouble code to find the initial condition on the lengthy check list which served you appropriately finding your cause and fix. Thank you for supporting proper diagnostics . It's tough sometimes but if we calmly sort out the good conditions from the bad , we can be successful as you are now.

 

[JPNinPA]

If the O2 isn't NTK you will have issues.

 

[greg92jeepxj]

X2. Hope the replacement O2 sensors were NTK ? Chrysler is finicky in this way .

 

[Scrambler62]

Guy's I always used NTK, I have a collection of them.
The fix was getting engine to temp faster with Spec 195 thermostat.
Jeep is running better than ever.
Never came across this fix in all my searches. Hope this helps someone with same situation.

 

[Scrambler62]

Forgot to say,
If you have a 195 thermostat and you have similar problems the thermostat could be stuck open, causing long heat up time, lower engine temp.
setting DTC, CEL

 

[Scrambler62]

Forgot to say,
If you have a 195 thermostat and you have similar problems the thermostat could be stuck open, causing long heat up time, lower engine temp.
setting DTC, CEL