The Check Engine Sign (Malfunction Indicator Lamp)

chmzzy · March 12, 2014

My car's dashboard shows a Check Engine Light. I serviced my car from Pitstop Three days ago and suddenly, today morning I saw this indicator. Do you know why this would happen and What should I do about this? Please share your advices. Thanks

Edited March 12, 2014 by chmzzy

Watchman · March 12, 2014

Three days is a long gap for a washing/cleaning related thing to come up. Don't presume that it's the indicator itself that is malfunctioning. It could be something genuinely wrong too. One thing you could do is take it to the agent or a mechanic and get them to check the engine. Basically, plug in the car to a computer and run a diagnostic.

Edited March 12, 2014 by Watchman

Niranjan de Silva · March 12, 2014

Well did you wash your engine bay with the high pressure hose? Also what is the vehicle and a few more details would be good to find a proper solution.

Davy · March 12, 2014

The check engine light is a general indicator to let you know that there is something wrong with either one or more inputs to the ECU. To get to know the actual issue, you should run a diagnostic scan as Watchman already mentioned.

The diagnostic scanner will show error codes which can be directly translated to what component has failed/lost connection. Even if the check engine light appears intermittently, the car's ECU stores the most recent set of errors reported until they are cleared. So even if the check engine light goes off, I suggest you still run a diagnostic to get to know what went wrong and take precautions of the same issue coming forward in the future.

VVTi · March 12, 2014

Check the plug leads, check to see if your petrol cap is closed, any loose connections/sockets... do the basic walk-around first.

chmzzy · March 12, 2014

Hey guys, Thanks for your replies.

I took the vehicle back to Pitstop and they were able to fix it. There was loose connection in one of the hoses.

This must have happened after the vehicle service!

Magnum · March 12, 2014

Didnt someone else also have an issue after washing his car?

I wash my car everyday but never had problems

E L N I N O · March 12, 2014

This happened to me once when I was leaving office in the evening, the check engine light came on suddenly. So I did the basic i-have-no-idea-what-i-am-doing stuff, tightening the plugs and sensors, looking all around the engine bay with a torch, but found nothing suspicious. I wanted to know whether the light came on due to a resident issue or due to a random loose connection sort of issue. So I disconnected the battery for a couple of minutes knowing that it would clear the error, and checked whether the light comes back again. I was planning to leave the car at office if it comes back but it didn't so drove it home very carefully It never came back agaiin and obviously I forgot the whole story. (later I ordered an obd scanner off ebay and found out all my fault codes have been cleared)

My questions are,

How stupid is to do what I did?

Do we need to worry if check engine lights comes on for no reason (obviously for a reason) and it never comes back when it's cleared?

If the light comes back again after clearing, how safe is it to drive it to a nearest garage?

Davy · March 13, 2014

On 3/12/2014 at 4:42 PM, E L N I N O said:
This happened to me once when I was leaving office in the evening, the check engine light came on suddenly. So I did the basic i-have-no-idea-what-i-am-doing stuff, tightening the plugs and sensors, looking all around the engine bay with a torch, but found nothing suspicious. I wanted to know whether the light came on due to a resident issue or due to a random loose connection sort of issue. So I disconnected the battery for a couple of minutes knowing that it would clear the error, and checked whether the light comes back again. I was planning to leave the car at office if it comes back but it didn't so drove it home very carefully It never came back agaiin and obviously I forgot the whole story. (later I ordered an obd scanner off ebay and found out all my fault codes have been cleared)
My questions are,

How stupid is to do what I did?

Do we need to worry if check engine lights comes on for no reason (obviously for a reason) and it never comes back when it's cleared?

If the light comes back again after clearing, how safe is it to drive it to a nearest garage?

I wouldn't call what you did stupid, cause some people don't even know what a Check Engine indicator is. Got a call from a friend of mine recently saying that there is an "orange box-like bulb" on the dashboard and what he should be doing. I think you get the picture.

Anyway, Looking around the engine was all good and you definitely would have noticed if it was something obvious like a loose connector or a disconnected vacuum hose. What I would have done differently is disconnect the battery because it would have been good if you got to know what actually caused the indicator to come on. You're lucky the error was just a one time thing, maybe the ECU got an incorrect reading from one of the sensors or maybe there was a one time ignition failure or something. Tightening the connectors and leads would have ensured connectivity.

About your second question, my opinion is that you really need to know what the actual cause is. Since the indicator itself is a very vague way of letting you know tha there is something wrong, I know that I'd lose a lot of sleep over thinking why the light came on. So the best thing is to just get it diagnosed (easy for you now since you have an OBD scanner) if a visual inspection doesn't cut it.

Is it safe to drive to the nearest garage... depends on why the indicator is on. While the car is perfectly driveable for some errors (the fuel cap being loose for example), the car completely dies in some cases. My car started to stall once and it could not be started until the engine was left to cool down for about 30 minutes. The indicator disappears after the engine is cooled down and would operate normally again for a few minutes/hours. Stalled over 4 times on my way to the mech and it was a nightmare driving while knowing the car would die on you the next second. Turned out to be the Cam Position Sensor. So how safe depends on why the indicator is on.

Rumesh88 · March 13, 2014

Just to add a line to what Davy has elaborated above, if the indicator is steady then it is only a warning and you can drive on safely until you get to the nearest garage if the vehicle is drivable. According to a report I read 10% (I could not believe the figure!) of the vehicles on US roads have their CEL on, but they just keep on driving. However if the indicator is blinking it can be a more serious problem like a misfire which could eventually result in burning the cat converter etc and if you are still compelled to drive, the advice is to reduce the vehicle load to a minimum and maintain a low speed until you get to a garage.

Edited March 13, 2014 by Rumesh88

YALA · March 13, 2014

also some vehicles are very sensitive to the battery if your having a weak or dying battery the car tends to give out random error codes. If you reset the codes and the error lights pops up again on starting the car up then you definetly have a cause to be checked on

E L N I N O · March 13, 2014

Thanks guys for your valuable input. I had the misconcept that if the check engine light comes on, it won't go away until it's cleared. Turns out it's not the case always. Too bad I cleared it and now no way to find out what caused it. Now I'm hoping that it would pop up again randomly