Skip the auto shop - Our mechanics make house calls

Q: Check Engine Light came on gave me a O2 sensor code. A week later the car broke down and won't start. It now has catalytic converter code.

asked by on

about 2 weeks ago the check engine light came on in my car. We plugged in the carmd and it gave us a code and we googled it and it was the 02 sensor. I was waiting until payday to get it fixed and the car seemed to be running fine. I ran to the grocery store (a mile down the road) and on my way home the car died not even 200 ft out of the grocery store parking lot. We towed it home as it wouldnt start (it sounded like it wanted to but just wouldnt). Once getting home we plugged the carmd in and it gave us a catalytic converter code. So my question is , is it my o2 sensor or my catalytic converter? There is a pretty big difference in the cost to fix the 2.The car is a 1 owner car. Always had routine maintenance and obviously very little use for the year and amount of miles. It was my elderly uncles car and he passed away a little over a month ago and he always took care of anything that needed to be done right away.

My car has 53000 miles.
My car has an automatic transmission.

A: It is helpful if you include the codes numb...

It is helpful if you include the codes numbers. There are numerous O2 sensor and catalytic converter codes. There are two O2 sensors on your car. One is monitors the fuel ratio and the PCM (powertrain control module) uses it to calculate fuel mixture. The other monitors the catalytic converter efficiency. The code number will designate which O2 it is.

When a car dies as it has, there is a time that the car will run bad. During this time, it will negatively affect the catalytic converter. Not to mention, if the O2 that monitors the catalytic converter is the one that needs to be replaced, both of these situations will confuse the PCM as to the condition of the catalytic converter. This code should not be acted on until the car runs again and which O2 is setting the code is made clear.

Neither of these will cause your car to quit running. The present situation needs to be diagnosed before the O2 or catalytic converter codes are addressed. There a several things to check and confirm when a car won't start. There are two no start conditions that need to be differentiated. Is it a no crank or a crank no start? One has to do with the starter system and the other has to do with the motor running. I am going to assume you car is a crank no start based on your description.

When we have a crank no start we need to check for the presence of fuel pressure, spark, injector pulse, and camshaft timing. Depending on which one of these is missing, this will determine the diagnostic path to be followed. Check for fuel pressure with a pressure gauge, check for injector pulse with a noid light, check for spark with an inline spark tester and check for camshaft timing by checking the compression of all the cylinders. It may become necessary to inspect the camshaft timing directly by disassembling the front of the motor.

If you should require further assistance with this, I recommend having one of or mobile technicians perform an inspection on your car's no start condition to pinpoint what exactly is at fault and make the necessary repairs to your vehicle. Best of luck.

Good luck!

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: No injector pulse but does spark.

Hello There, You are correct in that if the crankshaft position sensor or the pickup coil were bad there would likely not be any spark to the plugs. In relation to your no injector pulse problem, check the wiring harness...

Q: Loud, hot-rod type sound when driving

Hello. It sounds like the catalytic converter gaskets may be causing a leak in the exhaust system. It is also possible that there is a leak or bad baffle in the muffler. This may be causing the hot-rod sound. It...

Q: Getting my vehicle to crank

Hello. Thank you for writing in. With checking the ignition for a power supply, what other tests have you done? The first thing to always check in this situation is the starting system. Does that battery have at least 10...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...