I pulled codes with a OBDII code reader and it gave me three codes. (1) P1166- Primary HO2S (No.1) Heater System Electrical. (2) PO134- O2 Sensor circut no activity detected (bank 1 Sensor 1). (3) PO845- Transmission Fluid Pressure Sensor/Switch "B" Circut. What does this mean???

there are about a dozen O2 sensor codes. Tell us which one you have

Did you replace the right one ? This code does not necessarily mean the O2 sensor is bad . The code description say O2 heater " CIRCUIT " bank 1 sensor 2 Did you check the wiring , the fuse ?
P0141 - O2 Heater Circuit (Bank 1, Sensor 2) Description: See the description for DTC P0135. Possible Causes: See the possible causes for DTC P0135. Diagnostic Aids: See the diagnostic aids for DTC P0135. Application Key On Engine Off Key On Engine Running Continuous Memory All GO to Pinpoint Test DW . P0135 - O2 Heater Circuit (Bank 1, Sensor 1) Description: During testing the heated oxygen sensor (HO2S) heaters are checked for open and short circuits and excessive current draw. The test fails when the current draw exceeds a calibrated limit or an open or short circuit is detected. Possible Causes:

• Vacuum hose disconnected on exhaust gas recirculation (EGR) system module (ESM) applications
• Short to VPWR in the harness or HO2S
• Water in the harness connector
• Open VPWR circuit
• Open GND circuit
• Low battery voltage
• Corrosion or incorrect harness connections
• Damaged HO2S heater

Diagnostic Aids: Check the HO2S electrical connector for damage, corrosion, and water intrusion.
Damaged HO2S heater. Application Key On Engine Off Key On Engine Running Continuous Memory All GO to Pinpoint Test DW .

HYUNDAI OBDII DTC

P1100 Manifold Absolute Pressure Sensor Range/Performance
P1102 Manifold Absolute Pressure Sensor Circuit Low Input
P1103 Manifold Absolute Pressure Sensor Circuit High Input
P1123 Lang Term Fuel Trim Adaptive Too Lean
P1124 Long Term Fuel Trim Adaptive Too Rich
P1127 Long Term Fuel Trim Multiplier Too Rich
P1128 Long Term Fuel Trim Multiplier Too Lean
P1134 HO2S Bank 1 Sensor 1 Transition Time Switch (Bank 1 Sensor I)
P1154 HO2S Bank 2 Sensor 1 Transition Time Switch (Bank 2 Sensor 1)
P1166 HO2S Bank 1 Sensor 1 Controller Adaptive Diagnosis Fault (Bank 1)
P1167 HO2S Bank 1 Sensor 1 Controller Adaptive Diagnosis Fault (Bank 2)
P1168 HO2S Bank 1 Sensor 1 Heater Power Incorrect (Bank 1 Sensor 2)
P1169 HO2S Bank 1 Sensor 1 Heater Power incorrect (Bank 2 Sensor 2)
P1372 Segment Time Incorrect
P1400 Manifold Differential Pressure Sensor Circuit
P1440 EVAP System Vent Solenoid Circuit
P1443 EVAP System Fault (Fuel Tank Cap Missing)
P1510 Idle Control Valve Opening Circuit Shorted (Coil 1)
P1511 Idle Control Valve Command Signal Shorted (Coil 2)
P1513 Idle Air Control Valve Opening Coil Circuit Open (Coil 1)
P1521 Power Steering Switch Input Circuit
P1529 Customer Snapshot Request VIA CAN
P1552 Idle Air Control Valve Closing Coil Circuit Shorted
P1553 Idle Air Control Valve Closing Coil Circuit Open
P1586 Encoding Signal Circuit Not Rationale
P1602 Serial Communication Fault with Transmission Control Unit
P1605 Rough Road Sensor Circuit
P1606 Rough Road Sensor Circuit Not Valid
P1611 MIL Request Signal Circuit Low Input
P1613 ECU Self-Test Failed
P1614 MIL Request Signal Circuit High Input
P1616 Main Relay Fault
P1623 Diagnostic Lamp Power Stage Fault
P1624 MIL On Request Signal//Cooling Fan Relay Low Circuit
P1625 Cooling Fan Relay High Circuit
P1665 Power Stage Group 'A' Fault
P1670 Power Stage Group 'B' Fault

Hello there:
P1167 and P1166 codes relate to the primary O2 sensor heater malfunction.
there are two different O2 sensors, a "universal" sensor from Autozone and a supposedly OEM sensor from O'Reilly's. Both of them may cause the car to throw a p1166 or P1167 code and run rough. so i highly recommend getting a O2 sensor from Honda, and this will fix the problem .
It turns out that none of the aftermarket probes from Bosch or Denso will work on a ULEV (F23A4) 4 cyl. engine. Honda had different part number probes for the normal VTEC 4 cyl. and the ULEV Vtec engine and the probes look different and have different length cables. The computers at O'Reilly's, Autozone, or NAPA made no distinction between these two engine types.

and what is he bpt?? what does that refer to?

P1166. Primary HO2S (No. 1) Heater System Electrical.

Replace O2 sensor. Iif it smells rich then you are getting too much fuel. You may have a problem with the fuel pressure regulator or a leaking fuel injector. This can also be caused by bad oxygen sensors.

Hops helps (remember to rate this answer).

P1166 refer to O2 sensor heater circuits malfunction, HO2 Heater system electrical, bank 1.

Hi:
This code refers to the front oxygen sensor on Bank 1. Basically the oxygen sensor is inactive. Here's why:
The powertrain control module (PCM) provides a baseline voltage of about 450 mV on the oxygen sensor signal circuit. When cold, the PCM detects the the internal resistance of the sensor is high. As the sensor warms up the resistance is lowered and it starts producing voltage based on the oxygen content in the exhaust. When the PCM determines that the time it took for the sensor to warm up is greater than one minute or that the voltage is inactive (not reading outside 391-491 mV it views the sensor as inactive or open and sets the P0134 code.Potential Symptoms
One or more of the following may occur:

• Check engine light illumination
• Poorly running/engine missing
• Blowing black smoke
• Poor fuel economy
• Dying, stuttering

Causes A code P0134 may mean that one or more of the following has happened:

• Bad O2 (oxygen) sensor
• Bad heater circuit in the O2 sensor
• Wiring or connector to the sensor frayed / broken
• Blown heater circuit fuse
• Holes in the exhaust system
• PCM failure

Possible Solutions The most common fix is to replace the oxygen sensor. But that doesn't rule out the possibility of:

• Rusted exhaust pipe
• Inspect wiring & connector(s) for problems
• Excessive amperage blowing heater fuse (still requires replacement of sensor but also replacement of blown fuse)
• Replace PCM (only as last resort after all other possibilities are covered.

P1166 O2 Sensor - controller adaption diagnosis malfunction (bank 1).

Trouble area:

* P1166 is case for HO2S (Bank 1, Sensor 1) Signal line open
* Fuel system (Fuel tank/Pressure regulator/Fuel pump/PSV) failure
* Poor connection to fuel line hose/sealing/cut
* Sealing between purge valve and fuel tank
* Air leakage in exhaust system
* Ignition system (ignition coil, spark plug, cable) failure
* Surge tank and intake port failure

P0155 OBDII code refers to HO2S heater circuit - bank 2 sensor 1 , not knowing your engine size and engine vin code thats about as far as we can go with our answer . we can say bank 2 sensor 1 is the passenger side upstream oxygen sensor has a heater circuit problem , could possibly be a bad oxygen sensor . you ask what is that - thats what it is ... cheers .