Chrysler 300M engine light - o2 sensor?

My engine light is on (2002 Chrysler 300M). The car does not even have 60,000 miles although it is ten years old.

The primary codes that have shown on quick diagnostic are: p0135. ALSO once – possibly either p0141 or 441? (I don’t know the code as the the oil change shop erased the code before giving me the number. They think it said something about the o2 sensor or evap purge system…)

Yesterday I took the car to a local repair garage. He did not do a diagnostic as I already have the 0135 code from AutoZone. He said to apply the $90 (the cost of the diagnostic) to the repair. He said ideally I should have all 4 o2 sensors replaced. I can’t afford to have ALL replaced - I can barely afford to replace one. Is this a scam? Do I need to replace all 4 at the same time? Can I just replace the one that has gone bad?

How long can I drive with the 135 code - will it hurt my engine?

He also suggested that I erase the code, drive until the engine light comes on again and get that code too — then we’ll have stock of the various codes the car has been showing…


I would erase the code and see if it comes back. If it does, then just have the one sensor replaced, not all 4. This is the code for the front sensor on the drivers side and its not the sensor itself that has gone bad. This is a heated sensor and the heater circuit is not working. The first step is check the wiring, if it checks good, then the sensor has to be replaced. Checking the wiring should be part of your mechanics $90 diagnostic fee. If it’s not, then he is not doing his job and you should find another mechanic. AutoZone does not do wiring checks for you.

Since it is only the heater part of the sensor, there is no reason to replace any other sensors at this time.

How long can you drive with a P0135 code? Theoretically forever. The heater only operates when you first start the engine in order to reduce emissions during warmup. The exhaust gasses eventually warm up the sensor so that it starts operating normally. Many vehicles locate the front sensors so close to the engine that they don’t even need the heater.

But here is the downside, the CEL will be on all the time so you will not know if something else goes wrong. You could end up with more serious damage if you don’t detect any new faults. also if you have to pass a smog test in your area, you won’t until you get it fixed.

One more thing, the code for a purge control valve is most often caused by over filling the gas tank. If you keep adding gas after the pump handle first clicks off (topping off the tank), the gas will expand and liquid gas will enter the vent lines and getting into the charcoal canister. This will impede the flow of vapors during the vent cycle and give the code. The simple thing to do is never add gas after the pump handle clicks off. There are other causes for this code but that is the most common cause.

The other downside is with an oxygen sensor heater not working, if that is the case, it can take a long time for the engine to go to ‘closed loop’ operation. Which means you will get poor fuel mileage, likely reduced performance, and possibly be shortening the life of your catalytic converter(s).

I’d clear the codes, wait until the light comes back on, then see what codes you have, not guess based on a half-remembered conversation with someone. You can retrieve the basic codes on your car without a scanner by flipping the ignition on-off-on-off-on. (don’t start the engine) The codes will blink out on the check engine light with a pause between them—eg. 0441 would be four blinks, a pause, 4 blinks, a pause, then one blink. Then a pause and if there are more codes, they would follow. You might have to repeat the process to be sure what you’re reading. This will only display the codes, not clear them.

Reset the codes…(most auto-parts stores will do this for free) wait until the cel comes on again. Read the new code(s)…Fix what is wrong and no more.

For a few bucks you can buy a OBD-2 to USB cable and a basic diagnostic program that will allow you to use a lap-top computer to read your own codes and clear them without paying anyone $90 to perform this service…Cables are available on eBay…Here is one such adapter. There are many more.

Thanks much for your suggestions. Helpful!

You can also buy a Bluetooth device that plugs into the diagnostic port and communicates with a smartphone. This can be used to view and clear codes as well. I have the “Torque” app for Android that has a lot of monitoring capability as well as being able to view and clear codes, but there are many others, and I’m sure there are iPhone apps as well that do the same.

If you’re interested in going this route, Google bluetooth obd2 and you’ll find quite a few. I have a model made by ELM, and it works well. I’d avoid the super cheap no-name brands. Note: using a Bluetooth adapter for this presumes that you have the technical knowledge to at least pair a Bluetooth device with your smartphone, and are comfortable with installing an application and configuring it.