This Sucks!!! Got code P0136 and P0139!!!!
 

Great this really bites.... it points to the downstream oxygen sensor... one code says the circuit could be at fault... the other says it's a monitoring error... wtf should i replace it (for $145) or look for some other problem

Time for a new rear O2 sensor. Look at www.oxygensensors.com for a good price and mention maxima.org for a discount.

Get a universal sensor - wire it up yourself and save about $85. An O2 sensor is an O2 sensor - Bosch is a good name (what comes on the car stock, IIRC).

Trav