check engine light on with code PO138 is that before or after catalytic converter oxygen sensor?

Question

if after the catalytic converter oxygen sensor where can i find a good website that shows how to replace it(DIY) with pictures/photos without buying haynes/chiltons repair manual ? would adding fuel injector cleaner/seafoam/or the tightening the gas tank lid works ?

Answer 1

that code is pre cat easy to change and needs only a wrench

Answer 2

PO138 o2 sensor circuit high voltage (bank 1 sensor 2) This does not indicate a bad sensor. If it was bad there would be no signal or an erratic signal. High voltage could indicate a rich mixture in the exhaust system and possibly a bad cat. This sensor is after the cat. Bank one varies depending on where the # 1 cylinder is on the engine, left or right side. You need a scanner that can produce a graph to check o2 sensors properly. Injector cleaner in the tank may help as a dirty injector can cause rich mixture. You can add the cleaner and have Auto Zone or some auto supply turn off your check engine lite and wait to see if it comes back on. It won't go off by itself. If your car is a little sluggich or is starting to lack power you have a cat.problem. A continuing rich mixture will damage the cat by overheating it. NEVER replace a part till you know the problem.

http://www.autotap.com/technical_library.asp
Go here and get educated about sensors.

Answer 3

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How much did this dealership charge you for this "service"? It sounds to me like he was shooting from the hip, into the dark. "P0138" merely indicates that the circuit voltage for the Oxygen sensor is high. Why? Time for DIAGNOSTICS !! "P0420" indicates that the Catalytic efficiency has deteriorated below a threshold level that could cause emissions to rise to an unacceptable level. How does the computer know that? Time for DIAGNOSTICS !! There are tests to run for both conditions. It takes a while, and a qualified emissions shop could run both tests in less than a half an hour, though they would probably charge an hour's worth of time. The voltage could be high due to a dirty air filter, or contaminated oil. The sensors COULD be defective and need replacement, but it is unethical to spend the customer's money with such cavalier abandon. In many states, it is also illegal. It is impossible to tell by merely checking codes what is the cause of the failure. As for the Cat, the means for determining the efficiency is another oxygen sensor. That is all. Suppose that sensor is faulty? You may have replaced the cat for $1,800.00, and still have a failure. But they will cover that by replacing the sensor at the same time as the cat (and not tell you about it), or charge you for it as being "…the proper repair, with ALL the necessary parts. Find a QUALITY repair shop that specializes in emissions, preferably an ASE certified shop, and get another opinion, diagnostics, estimate, and CORRECT repair.

Answer 4

PO138 21 Downstream H02S shorted to voltage Harness and connector / Downstream HO2S

This code is for the O2 Sensor behind the cats.
Your O2 Sensor has gone bad.

The sensor is on Bank 1 Sensor 2. Meaning driver's side, sensor behind the catalytic converters.
This code is indicating the voltage the O2 sensor is detecting is too high. Generally a O2 sensor generates it's own electricity and send the signal to the computer to control the air/fuel mixture or to check to make sure the Catalytic converters are working efficiently. They usually have a range of 1-5VDC. The OBDII Computer on your car is detecting a high voltage. In your case, the O2 sensor involved is checking to make sure your cats are working.

When a O2 sensor goes bad, it is common to find this problem of high voltage triggering the code.

Answer 5

Well, you are talking about a dealership, $2300 is about right. Save yourself $ and chance out the Cat yourslef. First, I would just replace the O2 Sensors and see if its still throwing a code. Some times its some thing that simple that will fix it. Don't just assume that since your O2 (oxygen) sensor is throwing a code, that your cat needs to be replaced.

Answer 6

Po138 Code

Answer 7

after