I have a 2014 buick verano 2.4 ecotec. I was on vacation and my sister-in-law "ACCIDENTALLY" put diesel in it. She turned it on and it died pretty much rite away from what she said. She got it towed and she had a mobile mechanic come and drain the tank and put actual gas in it. It started but when it started the po420 code popped up. I replaced the oxygen sensors which did nothing and even tried the spacer for the downstream o2 sensor to keep it out of the exhaust which did not clear the code. Its running normal but I don't know what else I could do it what it could be? I have emissions coming up unfortunately and I'm hoping it's not the cat's but I'm thinking thats all it could be. Do you have any ideas?
In normal circumstances, P0420 usually indicates the catalytic converter needs to be replaced. Granted it could be upstream or downstream of the cat, but usually it is the cat.
But with diesel cars, they don’t have catalytic converters. Diesel burns “dirtier” than regular gas. Diesel have a special filter to help filter out diesel exhaust.
In your circumstance, by using diesel in a gas car, my guess since diesel is dirtier, it clogged up the catalytic converter.
Granted it could be upstream or downstream of the cat
what could be?
The culprit of the P0420.
P0420 sets when the oxygen storage capacity of the catalytic converter has degraded beyond a threshold.
Inspect for the following conditions:
- Verify there are no HO2S, fuel system, or misfire DTCs set
- O2 sensors are secure, and are OEM parts
- the wiring is not damaged, or contacting the exhaust
- The exhaust system for leaks, damage, or missing hardware
Turn on the car,
Connect an OBD2 scanner,
Let the car warm up for a while,
Go to live data,
Look at upstream and downstream O2 sensor values.
If only upstream is fluctuating, and the downstream too - it's likely to be a shot cat
(if you do not find other issues)
Otherwise, if the upstream is fluctuating but the downstream has one single steady ratio - it might not be cart.
Alternatively, reset the car's computers, go on a ride according to the requirements set in place by the I/M readiness monitors - what are the results?
