And now im getting P0138 and P2253 codes only when i start the car after a drive. If i clear the codes before starting the engine, it doesn't come on until i turn it off and start it again. Very strange.

Im using Cobb, is there a way to ensure that CEL doesn't come on again?

 

Why did you hook the wideband to the rear 02?

Did you cut and splice the wires?

 

I connected the white wire from the AEM gauge to yellow wire of the rear 02 sensor under the passenger seat. So my tuner can see wideband AFR on the logs as he is tuning my car remotely.

Yes i did cut the yellow wire and connected to the lengthened wire coming from my Wideband gauge.

Is there a way to turn off 02 sensor CEL with COBB? Or do i have to rewire the yellow wire to the rear 02 sensor again?

 

You should reconnect the 02 sensor properly and weld a separate 02 bung for the wideband.

Your CEL is probably due to an electrical issue from the splicing.

 

I do have a separate O2 bung for the wideband, but in order to see the logs via OBII, i had to spile into the connector going from rear 02 to PCM and feed it wideband signal coming from AEM wideband.

 

For P2253 Double check the connection for the front o2 sensor, its required. It may be damaged.

P0138 is fine if you have the wideband sensor hooked up. The o2 sensors are low voltage sensors (0-1 volts) and the wideband is feeding it 0-5 volts.

 

OP, did manage to solve it? im having the same problem but slightly different. i got the codes p2252 and p0037. but if i disconnected the ground wire (from the orange wire) the only code i get is p0138 which is fine but the AFR readings will be 1.1 richer on the AP.

 

p2252 indicates a negative signal is being fed.
I imagine it's hooked up backwards. (Positive coming from the gauge is hooked to the negative, and negative coming from the gauge is hooked to the positive feed)

 

As stated above fix the stock wiring and put the wideband in another bung. It can be in the testpipe or near the rear 02. Depending on what exhaust company you have. But usually there is a extra bung somewere on the exhaust

 

I made sure that the yellow wire connected to the white wire from the WB gauge. If im facing the connector, the yellow wire is at the bottom and right. But when i look at the diagram it says the yellow is #3 which is to the left. Can someone confirm?