Here are some test that you can do to try and figure out what is happening. Hope this helps.
80) DTC P0136, P0156, P1137, P1138, P1157 & P1158Continuous Memory DTCs P0136 and P0156 indicate output voltage of downstream HO2S is not within calibrated limits. KOER DTCs P1137 or P1157 indicate PCM does not detect output of HO2S in a calibrated amount of time (lean condition). DTCs P1138 or P1158 indicate PCM does not detect output of HO2S in a calibrated amount of time (rich condition). DTCs P0136, P1137 and P1138 are for HO2S-12. DTCs P0156, P1157 and P1158 are for HO2S-22. Possible causes are:
DTCs P0136 and P0156 can be set when leaks exist in exhaust system between engine and rear of catalytic converter. Possible causes are:
Inspect exhaust system including catalytic converter and HO2S. Repair as necessary.
Check HO2S Ground Circuit In PCMTurn ignition switch to OFF position. Disconnect PCM connector(s). Using a DVOM, measure resistance between PCM harness connector PWR GND and SIG RTN terminals. If resistance measurement is 5 ohms or more, replace PCM.