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Are you getting both the same codes back or just one of them? What did the shop say about their work? Do you have California emissions?
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Bank one sensor one is on the exhaust manifold and the wire is strapped to the upper radiator hose and the connector for it is by the back of the cylinder head if you have a 4 cylinder like you mentioned above.
Please clarify somethings for me. P1135 is a California spec code only for the AFR sensor which is different from a O2 sensor. They just look the same. You said you do not have California emissions. Can you recheck the code numbers. P0135 is a heater malfunction for the B1S1 non California emissions. A heater circuit malfunction will not set a P0171 code either.
I have to step out for a couple of hours and when I get back this evening I will post all of the info you need to make your head hurt. It is a 4 cylinder and not a V6 and you are certain of the code numbers correct?
Check back 11pm or so EST
The P1135 is a low current malfunction on the AFR heater circuit of bank 1 sensor 1. Ideally you need to test the voltage at the computer Pin HTAF it should read 12 volts. With in a minute or two the voltage should drop to 0 to 2 volts when the computer turns the ground circuit on to energize the circuit and heat up the sensor. If the voltage is not 12 volts then you need to check the voltage at the sensor. If the computer never drops the voltage then the driver is bad in the computer. 90% of the time the AFR sensor is bad but in some rare cases I have seen them take out the computer also. Click the link below for some more info. Theoretically the P0171 could set if there is an exhaust leak just befor the AFR sensor but it is virtually impossible on this engine. About the only way to set a P0171 code is because of fuel restriction or low pressure becasue of the MAP sensor on this engine.