while doing my 0-60 test a service engine soon light came on. It's come on before and gone away after a few days but this time it's not going away. I don't notice anything wrong with it, still idles the same, no loss of power, it feels the same as when the light was off. Any ideas, maybe a bad O2 sensor? I just want to know if it's still ok to drive until I can go get the code read
Service engine soon
- Thread starter 02_Tahoe
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David Smith
Full Access Member
Mine just did that a few days ago. I was passing someone and it came on. Got it scanned and it was a knock sensor. After about 3 days the light went back off and has not returned yet. Hopefully it doesn't.
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02_Tahoe
Full Access Member
Idk what that is but it doesn't sound good
David Smith
Full Access Member
It basically tells you motor when it advance or retard your timing from what I understand. You can go to any parts store (Advance, Auto Zone, O'Reilly) and they can scan your truck for free and tell you exactly what it is. Also, maybe have them clear it if they are willing to, and see if it comes back. Mine went off by itself.
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02_Tahoe
Full Access Member
I just looked up what it is. Like you said changes timing, and you'll feel a difference in performance, but like I said, nothing is different, it performs the same. And if it's the knock sensor, do I replace the sensor to fix it? Or fix something that caused the knock
David Smith
Full Access Member
Mine did not have a change in performance either. Maybe that is why it went back off after a few days. Might have gotten some bad gas or something. The "knock" is going to happen. The knock sensor is what detects it and makes the necessary changes to the timing. There are 2 knock sensors. You have to remove your entire intake manifold to change them.
If it were me, I would give it another day or two and see if it goes off, or just have someone clear the code (assuming that is what it is) and see if it comes back.
Step one would definitely be to have it scanned and see what the code is anyways. Could be something stupid.
If it were me, I would give it another day or two and see if it goes off, or just have someone clear the code (assuming that is what it is) and see if it comes back.
Step one would definitely be to have it scanned and see what the code is anyways. Could be something stupid.
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02_Tahoe
Full Access Member
Man I hope it is something stupid. Although replacing a knock sensor isn't that expensive, I could do it myself
David Smith
Full Access Member
It should not be too difficult. There is a lot of stuff to undo, but if you just take your time, it should take more than a few hours.
iamdub
Full Access Member
If the light comes on then goes off, then the problem was a single isolated incident that hasn't reoccurred within a certain number of drive cycles. If it stays, you have a hard failure. Also, if the code defines as "knock sensor signal high/low or O2 sensor signal high/low, etc.", that doesn't necessarily mean that particular sensor is bad. It just means that sensor reported to the PCM something outside of it's allowed/expected normal operating range. Either there is/was a fault and the sensor detected it as it was supposed to do or the sensor is faulty and erroneously reported a fault that didn't/doesn't actually exist.
The the whole OBD thing is not to police the sensors. It's to point you towards the area where you should focus your diagnostics attention. It's up to the person diagnosing it to use all the info available to determine what the problem is, whether it be a "lying" sensor or an actual problem within the system that sensor monitors. Ever heard of "Don't shoot the messenger"? The sensor is the messenger in this sense.
If the light is on and not flashing and the engine is running fine/normal (no sudden drop in power or MPG), then it's probably an emissions code and nothing detrimental to the engine. Plenty of places will scan codes for free, so there's no reason not to at least have this first step done. Just be aware that, especially if you go to Autozone to have the code(s) read, they're very quick to try to sell you whatever sensor(s) the code(s) relate to. Many buy whatever sensor(s), replace them, have the code(s) cleared, then the same code returns. This means either the new sensor is faulty or the problem is not with the sensor, but with the system that the sensor monitors.
Just get your codes read and report back here so hopefully we can help you not waste time and money.
The the whole OBD thing is not to police the sensors. It's to point you towards the area where you should focus your diagnostics attention. It's up to the person diagnosing it to use all the info available to determine what the problem is, whether it be a "lying" sensor or an actual problem within the system that sensor monitors. Ever heard of "Don't shoot the messenger"? The sensor is the messenger in this sense.
If the light is on and not flashing and the engine is running fine/normal (no sudden drop in power or MPG), then it's probably an emissions code and nothing detrimental to the engine. Plenty of places will scan codes for free, so there's no reason not to at least have this first step done. Just be aware that, especially if you go to Autozone to have the code(s) read, they're very quick to try to sell you whatever sensor(s) the code(s) relate to. Many buy whatever sensor(s), replace them, have the code(s) cleared, then the same code returns. This means either the new sensor is faulty or the problem is not with the sensor, but with the system that the sensor monitors.
Just get your codes read and report back here so hopefully we can help you not waste time and money.
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02_Tahoe
Full Access Member
The part about the light staying on and not flashing definitely makes me feel better, and mpgs are actually better now because I've been driving it easier with that light on, lol. I can't get to autozone today because I have work after school but I'll go Friday and report the codes. Also glad it's nothing serious because I'm going to the D.C tuning even Sunday for Justin to tune it
