I took my car to an auto center after the check engine light came up. I bought a universal Denso o2 sensor and replaced the bad sensor. I made sure 100% that all the wires were connected correctly. I then disconnected both battery cables for about 15 minutes to reset the computer. A day later the check engine light came up again. What could be the problem? The p0137 code says that the secondary o2 sensor has low voltage.