Diagnosing a BAD oxygen sensor that's making the check engine light light (CEL) up with a P0141 isn't hard at all.
In this tutorial, I'll show you how to do it with a multimeter. This article applies to several GM makes and models... you can check out the ‘Applies To:’ chart on the right column to see if your vehicle is included.
In case you're wondering, where the oxygen (O2) sensor that the code P0141 is accusing of being BAD is... this bad boy is located on the exhaust pipe after the catalytic converter.
To help you navigate this article, here are its main points:
If the heater element within the oxygen (O2) sensor goes bad, the PCM (Powertrain Control Module = Fuel Injection Computer) will light up the check engine light (CEL) on your instrument cluster.
You'll also see one or several of the following symptoms of a BAD oxygen sensor heater:
Here's a basic list of tools you'll need:
The oxygen (O2) sensor has to reach a certain temperature to activate and start measuring the oxygen content of the exhaust.
As surprising as it may seem, the temperature of the exhaust gas isn't enough to keep the oxygen sensor hot enough to perform 100% of the time.
The solution? Place a heater element inside of it so that it stays hot as long as the PCM commands it.
The only thing that sucks about this... is that the heater element (inside the oxygen sensor) doesn't last forever and fails very frequently.
If you take a close look at the connectors (engine wiring harness connector and the O2 sensor connector), you'll see that four letters are embossed on both of them.
These four letters are A, B, C, and the letter D. These are the letters that you'll need to test the rear oxygen sensor with the instructions in this tutorial.
IMPORTANT: One last thing... the wires have colors only on the engine wiring harness side AND THESE COLORS MAY NOT MATCH THE ONES ON YOUR VEHICLE (On the oxygen sensor side... there's really no dependable way to identify the circuits with their colors). But this is no cause for concern, since you can still identify them with the letters embossed on the O2 sensor connector.
Just to further clarify this, if the colors in the chart below don't match those for the rear (post-catalytic converter) oxygen sensor.... you can still use the info in this article! Since the circuit descripitions are the same, all that you have to do is identify the wire by its letter.
|Heated Oxygen Sensor Circuits|
|A||Tan w/ White stripe||HO2S Low Signal|
|B||Purple w/ White stripe||HO2S High Signal|
|C||Black w/ White stripe||Heater Element Control Circuit (Ground)|
|D||Pink||Heater Element Battery Voltage|
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