Ignoring CEL

[Chris Meutsch]

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I've told the story here before. My former indy mechanic specifically brought me out a Mercury Cougar instrument cluster and showed me a tiny hole drilled into the side of the cluster, right where the CE light was, disabling it permanently. Some other shop did this maliciously and put it all back together and who knows what they charged.

And we all know Homer is an idiot.

 

[Nukeman7]

Mine has been on since 2020 for oxygen sensors. Problem is the car is from New York and really rusty and the oxygen sensors just round off when I try and take them out. So I don’t want to spend the money on a new exhaust with 230,000 so I’m just going to ride it. I mean yeah gas mileage suffers but it’s more pain than it’s worth to replace the exhaust.

AM, I'm dismayed that you would tolerate this situation for 5 years knowing that you are a professional mechanic at a dealership. Don't you have access to an acetylene torch (AKA, "blue wrench") to loosen up the oxygen sensors?

 

[AutoMechanic]

AM, I'm dismayed that you would tolerate this situation for 5 years knowing that you are a professional mechanic at a dealership. Don't you have access to an acetylene torch (AKA, "blue wrench") to loosen up the oxygen sensors?

I’m just cheap lol. I do like using the torch though because it makes one guy in the shop mad. Honestly most of the mechanics I know would also let it roll. Now if it was a misfire or something I’d fix it immediately but something harmless… let it ride.

 

[HowAboutThis]

I ran with a P0420 in a Civic for about 50k miles. Gas mileage never suffered, performance never suffered, one Honda tech said the emissions stuff is so sensitive you can often go quite a while with lights on if it's something like a P0420. He said there's obviously risk, but given the car was worth about $4k at the time, he said as long as I knew the risks it was up to me to fix or not (cat going bad). I'd reset it and it'd come back every month or two.

 

[Auto tech]

Most definitely I have seen problems with people ignoring cel. Specifically ruined cats from misfire codes, saw burned valves, destroyed cam phasers, busted timing chains you name it. All those problems should be caught by OBD2 systems in advance

 

[wtd]

I would tell your brother to not call you if his car eventually breaks down and no longer runs. If he is too cheap to do maintenance and repairs, I would be too cheap to help him out.

Depending on why the CEL is on, sometimes ignoring it can lead to long term expensive damage.

 

[Skippy722]

CEL has been on in my truck since 28k miles. It’s an EVAP code and I don’t have inspections. It will live like that till it goes to the junkyard. Van has one for a thermostat, that will get fixed properly.

 

[siriusc1024]

On a lot of Fords if you ignore the CEL's about ignition coils it'll eventually take out the ECU.

 

[siriusc1024]

I've told the story here before. My former indy mechanic specifically brought me out a Mercury Cougar instrument cluster and showed me a tiny hole drilled into the side of the cluster, right where the CE light was, disabling it permanently. Some other shop did this maliciously and put it all back together and who knows what they charged.

And we all know Homer is an idiot.

Key on engine off the CEL should be illuminated. This is meant as a test for functionality.

 

[siriusc1024]

Mine has been on since 2020 for oxygen sensors. Problem is the car is from New York and really rusty and the oxygen sensors just round off when I try and take them out. So I don’t want to spend the money on a new exhaust with 230,000 so I’m just going to ride it. I mean yeah gas mileage suffers but it’s more pain than it’s worth to replace the exhaust.

If it's one of the front O2's it can swing the fueling on a bank of cylinders. Too lean and burnt valves. Too rich means fuel washes oil off the walls accelerating wear.

Trick I use for oxygen sensors is to heat with a regular propane torch. Apply wax instead of PB. It'll wick right in without evaporating. Take it off with a small 6 inch pipe wrench. The threads will strip before that pipe wrench slips.

Recommend Denso O2's. Always replace O2's in pairs (upstream or downstream).

 

[RaymondP]

Seems like CEL comes on with older vehicles but sometimes goes off again by itself, particularly when longer journeys occur. Always worth investigating, particularly if nothing else appears amiss. In my case was the emissions system on an old Mercedes E350 4Matic (W112). My wife's beautiful car. Eventually CEL remained on but helpful to be forewarned.

Used OBD 2 to identify failing coil pack on another occasion. Again intermittent CEL came on but it was obvious (rough running) something was amiss.

 

[gasman556]

I don't understand it.
I'm always doing PM to my car.
Taking personal pride in knowing it's well maintained.

My brother on the other hand is the opposite.
One year ago, he tells me his CEL keeps coming ON.
He drives a 2018 Subaru Outback with 140,000 miles.
His fix is to disconnect the battery and the CEL goes out.
One day he's driving and I say, "pull into this AAP and they'll check for codes"
Something about - cylinder #3
My brother is cheap, but did then purchase a Code Reader.
He takes it to a machanic who threw parts at it.
Then, he went to who I suggested (they are very good at diagnostic work).
All was fine, but eventually the CEL came back ON.

Now my brother uses his Code Reader to 'delete' the codes.
His friend tells him to just ignore it and only worry when the yearly inspection is due.

I just had to get that off my chest.
There is NO chance my brother will read this and recognize me.

Question: Anybody have a horror story from ignoring the CEL ?

When I was younger and didn't know my @ss from a hole in the ground, I ignored mine for around 10k miles. It was for a bad o2 sensor. I kept disconnecting battery, etc and didn't have the money to fix it immediately (in school, etc). After graduating and getting a job, I got the code read and guess what? Ignoring it for all those miles ultimately cost me the replacement of both cats due to running rich for those miles the o2 sensor wasn't reading right. Lesson learned for sure. I actually replaced the o2 sensor myself right before the cats got replaced to save money as I still wasn't rolling in dough. Lots of learning from that experience for sure. TBH, that's also where I started amassing tools to work on stuff myself as I knew it was important. After both new cats and a new o2 sensor was put in, I drove the car for another 25k uneventful miles before trading it in.

Tell your brother he's an idiot and to cut the $hit on ignoring his CEL. That, or sell his car and get something else before his headgasket goes. My $0.02 and experience anyways.

 

[wavinwayne]

I drove my old VW GTI with the CEL on for over 250K miles. It had a secondary air injection fault code that I couldn't have cared less about.

 

[bubbanik]

If the CEL is flashing then you could damage an emissions component like the cat. I do not think I have every had a flashing CEL however.

Right before Hyunkia blows up the CEL starts to flash like crazy!
First and only time I've ever seen one.

 

[2strokeNorthstar]

Just got back from a week trip to Mexico. I think every car I rode in had either the CEL on, the TPMS light on or both.

 

[D60]

Just got back from a week trip to Mexico. I think every car I rode in had either the CEL on, the TPMS light on or both.

And everyone around you was driving with their hazards on? . That's been my experience in MX -- they think hazards are just normal. So a flashing CEL probably fits right in.

Seriously though, this crowd is funny. If you don't have inspections most people-- and especially working families -- will ignore cat efficiency codes. It doesn't affect how the vehicle performs, it's rarely just a bad downstream sensor, most people don't have the know-how or time to try a spacer, and cats aren't cheap.

It's difficult to spend $1k+ on cat(s) when the mortgage is due, the kids need back-to-school stuff and the vehicle runs fine. Sorry not sorry -- some people here live in a bubble.

 

[nickaluch]

Check engine light on my work beater has been on for probably 4 years car runs fine. Month before my inspection fill gas tank with 93 octane and bottle of Techron by second tank light goes out get my inspection. Back to 87 octane gas for the next 11 months with the check engine light glowing at me.

 

[Arc]

Cars in the pre-OBD era did not run better or longer!!

fuel injection was the last good addition to vehicles. Everything after that was nonsense.

 

[Dave Sherman]

I confess I ignored a CEL on the wife's car for more than a year. It was the clogged ports on the air injection system, a common issue on an Equinox 2.4. It ran fine, it was just complaining that the air injection flow was too low during warmup. Made a few attempts to fix it, but finally conceded I should pay the man to take the exhaust manifold off and clear the carbon from the injection ports because e-check time was coming up again.

 

[KrisZ]

“If it keeps on rolling, you keep ignoring”.