Is it safe to ignore a check engine light if the car drives fine?
When a car drives normally after a warning light comes on, drivers face a gamble between ignoring a potential catalytic system failure and spending thousands on repairs that might uncover deeper issues. This uncertainty makes it difficult to know if fixing the problem will actually secure the vehicle's long-term longevity or just waste money.
What the numbers show
Counted from the threads quoted below. How we count
- The most recent one is from October 2026.
- This comes up 9.1× more often in r/MechanicAdvice than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Driving the car until the fuel tank emptiesDid this help you?
- 2Using fuel system cleanerDid this help you?
- 3Switching to a higher octane fuelDid this help you?
- 4Having a mechanic clear the diagnostic trouble codeDid this help you?
- 5Buying a new or different vehicle and taking on new car paymentsDid this help you?
- 6Sourcing a used low-mileage engine or a donor car with a compatible engine from a marketplace or auctionDid this help you?
- 7ignoring the warning light and running the vehicle in two-wheel drive modeDid this help you?
- 8getting rid of the vehicleDid this help you?
- 9riding them out until they fail completelyDid this help you?
- 10replacing the injectors immediatelyDid this help you?
- 11Trading in the vehicle before complete failure.Did this help you?
- 12Monitoring the fluid level and cleaning the area with brake cleaner or solvent to check for new wet spots.Did this help you?
- 13Trying to ignore the noise and move onDid this help you?
- 14Lifting the cover to investigate the source of the soundDid this help you?
- 15basic maintenanceDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“If i drop around $2000 to fix the engine, will it be worth it? Im afraid they’ll be some underlying problems, but I’m really shooting for longevity.”source ↗
“Would that be that simple or do I to have to have a deeper look into my catalytic system?”source ↗
“Should I just ignore it or have a look at the catalytic system?”source ↗
“I am tempted to just ignore the light and let it run in 2wd mode. Do I risk damaging the transmission and other systems if I don’t it fixed?”source ↗
“four of them passed four of them failed according to them the ones that failed showed low output at various test points, which were around 9 to 10 cc low. Do y’all think I should just ride these injectors till they go out? Is that risky or should I replace injectors?”source ↗
“Injector place said I could ride them with no misfire or anything but they would probably replace them but as I said, I just got the car spent 200 to get them cleaned and was wondering if I should ride it out”source ↗
“got my oil changed today and everything was good but i’m “leaking oil” asked the bloke if it was serious and if i needed it fixed he said nah just monitor it. Just need advice if i should get it looked at again?”source ↗
“My girlfriend has a 2018 Toyota CH-R 110k miles with a bad bearing in the transmission.”source ↗
“No shop will open it up and replace the bearing of coarse.”source ↗
“Anyway, my question is should I wait until the transmission fails or is it going to fail in a way thats dangerous?”source ↗
“I’ve been contemplating a new engine because I work from home. What is a reasonably cost to have one put in?”source ↗
“There is something wrong internally and the garage told me it’s going and to take it to the dealership. I took it to the dealership and they’re like your engines going it’s $7k-$10 to replace 🤮.”source ↗
Where this came up
People with this problem also raised
- 15How to tell if a worn timing belt actually needs replacing
- 3Is it worth fixing an AC leak or just keep adding freon?
- 2How do you know if you have carbon buildup?
- 22Why does the check engine light come back on after replacing a sensor?
- 14Are new brake pads with a chipped corner safe to use?
- 3Should I fill a tiny windshield chip or leave it alone?