What Causes Trouble Codes P0052, P1129 and P0406?
The trouble codes you've mentioned, except for P0406, are related to your vehicle's Bank 2 Oxygen Sensor 1; this is the oxygen sensor on the engine side which cylinder 2 is located and it refers to the oxygen sensor located before the catalytic converter (pre-CAT). We suspect that this oxygen sensor is defective, as P0052 - OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1) - suggests that there is a problem with this O2's heater circuit.
P0052 - OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
We recommend making sure there is no break in the oxygen sensor wiring and connector, as well as checking for proper voltage and ground at the O2 terminals leading from the computer. An aftermarket oxygen sensor (aftermarket) should roughly run around $50.00, plus an hour of labor to replace. This does not include the diagnostics time which will be required to determine whether the sensor is actually defective or the wiring has a problem. You'll want to be certain the sensor is defective before spending any money replacing it.
P1129 - OBD-II Trouble Code: Closed Loop Fueling Not Achieved Bank 2
P1129 is common to see when there is any trouble related to the oxygen sensor. Closed loop means the engine has sufficiently warmed up and fuel delivery is now being adjusted by input from the oxygen sensor(s). When an oxygen sensor is defective, and incorrect data is being delivered to the computer because of it, the computer will not allow the engine to go into Closed Loop; which is what is probably happening here. The engine control computer has identified a problem with the O2 sensor and triggered a P0052. The same problem with the oxygen sensor is also not allowing the engine to go into closed loop; thus triggering a P1129. You can see these two codes are related. Once the P0052 is corrected and the engine codes erased, more than likely neither code will return.
P0406 - OBD-II Trouble Code: Exhaust Gas Recirculation Sensor "A" Circuit High
The curve ball... P0406 is the only code here not related to the oxygen sensors and rather the EGR sensor, unless the fault which is triggering the P0052 (defective heater circuit in the O2) is due not to a problem with the o2 sensor itself but rather with the electrical wiring leading to the sensor, and the same electrical wiring which leads to the O2 sensor also leads to the EGR valve sensor... and so now, both sensors show as defective when the actual trouble is with the electrical wiring. If this is in fact the case and the problem is within the wiring to both sensors, we'd recommend inspecting both sensor terminals for good ground first and then 5v voltage. You'll need to back probe from the sensors to the computer and good ground. It is possible the ground and/or 5v to these sensors originate from the same pin on the ECC (engine control computer). Should you find no electrical trouble in the wiring and proper ground and voltage exist at the sensor terminals, P0406 is pretty straight forward. There is either a problem with the EGR valve itself, i.e. the solenoid in the EGR valve (electric EGR valve) is bad, the EGR valve sensor (located within the EGR valve) is defective, or excessive carbon build-up in the EGR valve is not letting the valve open and close properly. By removing the EGR valve it'll be easy to see how much carbon has collected in the valve, and by applying 12 volts to the valve you should be able to see if the valve solenoid has movement. The EGR valve has a built in sensor. The sensor has reference voltage of 5 volts from the engine control computer. The 5v voltage from the computer as well as the reference voltage out of the sensor must be tested as well. With a P0406, more than likely the problem is with the EGR sensor component rather than the solenoid inside the EGR valve. On average this component (aftermarket) runs around $75.00. Replacing it will usually take around 1.5 hours of labor; not including diagnostics time. As with the O2, don't replace it if it only needs cleaning. Spending a little money on diagnosis will save you a lot of money on parts.
Once you've repaired the fault, remember to clear the computer of the trouble codes. You can use a scan tool to reset the computer. The check engine light should turn off. Drive your vehicle for at least 200-300 miles and over the course of a few days. You'll need to do this for two purposes. One, you'll want to see if you've really fixed the problem, ensuring the check engine light or malfunction indicator lamp no longer illuminate, and second, your vehicle will need to complete a Drive Cycle in order to get the Emission Monitors complete and the vehicle ready for the smog test.
