Rick's Free Auto Repair Advice

OBDII trouble Codes

OBDII trouble Codes

I can’t tell you how many times forum members write in and say, “The computer said to replace the oxygen sensor. I replaced it and now it says to replace it again.” Let’s get one thing straight…..the computer NEVER says to replace a part. It only tell you what condition the OBDII trouble Codes.

Here’s a typical example:

P0137 – Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2)

Now most of you would say the computer has determined that the oxygen sensor is bad. That’s NOT what the code says. It merely says the circuit voltage is low. Low voltage on an oxygen sensor is almost ALWAYS caused by a vacuum leak. Why? Because as air gets into the system, the air/fuel mixture is too lean. A lean mixture produces a low voltage on the oxygen sensor. Replace this oxygen sensor without fixing the vacuum leak and you’ll get the exact same code again. Only this time, you’ll be out $80 for a sensor.

How can you tell if you should replace the sensor? Get a REAL scan tool. Then learn how to interpret short term and long term fuel trims. It’s actually very easy. Read this article on scan tools.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat


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