View Full Version : Check Engine Light

23rd Jun 2016, 06:02
On the dashboard.
Tells you a whole bunch, doesn't it?
Tells you to go spend some money for a diagnostic at the dealer.

If car electronics are so damned smart these days and have these fancy screens - why can't the fancy electronics display the exact problem on the screen?

You know , like some aircraft.

23rd Jun 2016, 06:16
Buy a cheap dongle, plug it into the diagnostics port, download an app onto your phone or tablet and read off the fault codes yourself.

Effluent Man
23rd Jun 2016, 06:30
The trouble is they tend to present you with a list. Engine lights most of the time relate to things like oxygen sensors, air flow meters and clogged exhaust recycling valves. The cheap fix is often to give it a bath in brake cleaner in the case of EGR valves. They often are especially problematic when used in heavy traffic and sometimes fix themselves when you have a decent run. My mechanic used to say "Give it a good frashing".

Ascend Charlie
23rd Jun 2016, 08:24
I had one last week, the spanner was showing plus the outline of the engine, and the message "Check pollution control system".

A detour to the service centre, an hour or so in the waiting room, and the tech came back with the answer:
A floor mat had slid up the floor and got right under the throttle pedal, so it didn't have full travel, and the drive-by-wire system decided something was wrong. "Pull the mat, you gunky!"

Red face, but they didn't charge (because I have 3 of their vehicles in the garage).

23rd Jun 2016, 08:38
Cheap - about £20 - code readers are available on eBay.They are adequate for the home mechanic to be able to isolate a fault. Just plug it into the diagnostic port and push a button.

23rd Jun 2016, 08:49
It's all covered (possibly after any adverts. :rolleyes: ) here:


:D :D :D

23rd Jun 2016, 09:54
I've had a code reader for years, as they aren't model-specific, all use the OBDII port that all cars now have. It takes just a few minutes to read out what the fault really is.

Every time I've had occasion to use my code reader the fault has been a false alarm. For Toyota's (don't know about other makes) false alarms can sometimes be cleared by starting and stopping the car a few times (three I think, but I can't be sure). Failing that you can clear them with some code readers (the one I have allows faults to be cleared, as well as some dealer-only settings to be changed, like turning off seat belt warnings and the annoying internal reversing beep).

Ancient Observer
23rd Jun 2016, 11:52
My daughter's car, a Seat, kept losing power. Sometimes in very dangerous situations. (Outside lane of motorway).
Light came on after event. Was not on when car taken to dealers. Seat denied all responsibility. Refused to test it themselves. Garage could not replicate the fault.

Eventually, after telling me to try to kill my daughter by experimenting with her as driver of a death trap, I persuaded them to take it to the VW group test centre.

They replicated the fault, and gave us a new car.

Beware electronic stuff on cars!!

Loose rivets
23rd Jun 2016, 13:38
Yep, my BMW still does that hesitation thing, though the only warning is a sudden loss of fuel flow for say, one second. The tickover flow remains okay.

I had the computers out last night. Valvetronic (see my thread about computer voice) and the main CPU. I hoped the power down and rubbing the massif number of pins might just cure it. It hasn't done it for a couple of weeks so is so difficult to diagnose. Some days it does it several times in an hour.

I'm sure it's a commanded clip of the fuel, but the decision's logic escapes me.

I took it out to get the numbers so that I could borrow another CPU. It has to be one of the same group and then I'm assured it will run.

23rd Jun 2016, 14:26
Get one of these:


Runs forever and no fancy/useless engine lights.
Problem solved.

23rd Jun 2016, 14:34
If car electronics are so damned smart these days and have these fancy screens - why can't the fancy electronics display the exact problem on the screen?

Did you look on the top right corner of the screen and see a silhoutee of a driver pictured ?

Loose rivets
23rd Jun 2016, 15:11
I kept looking at my mountainous spelling mistake but it didn't really click until my tea caused my intellect to pique.

23rd Jun 2016, 16:00
My kid got me a Bluetooth enabled OBDBII that turned out duff. Got another one for very few dollars.

Then install Torque on phone.

DO NOT mount the mini CD supplied with the reader. Likely PLA equivalent of Stuxnet:E

The rear O2 sensor code pops up in Subaru, most usually because of leak, loose joint in exhaust system.

Torque can turn off the code, but certain jurisdictions will fail your emissions test if codes have been recently turned off:uhoh:

23rd Jun 2016, 16:34
my Subaru Legacy shows the "check engine" and the "VDC OFF" lights together every so often. It has been doing this for all of the 9 years I have had the car and the Subaru main dealer is unable to find the reason, despite it being one of my gripes at nearly every service. I have stopped worrying about it as they always goes out after a few minutes and rarely return for a month or two. When the lights are lit the performance of the car is marginally reduced, I suspect that VDC and traction control are related systems and it backs off the power to stop wheel slippage. Everything else performs normally.

Windy Militant
23rd Jun 2016, 21:58
My Octavia thinks it's funny to light up the little oh no you've got a bulb gone light. It then sits there sniggering while I look for the duff bulb. It usually, but not always, does this when it's raining. If I then turn the ignition off and back on it denies all knowledge of having a blown bulb. Still if it keeps it happy I guess I'll indulge it!

23rd Jun 2016, 22:09
All very well having your own diagnostics gizmo but unless it's only a duff bulb you'll have to take it to a garage to get it fixed. Modern cars are too complicated for mere mortals to repair.

23rd Jun 2016, 22:15
Happened a few times due to:

1. Forgot to tighten the fuel cap fully. (System doesn't register correct pressure.)

2. Had to use Regular fuel once, not Premium.

3. Unknown causes.

Fix in each case was to disconnect the battery lead and reconnect. Voila!!!

(Then look for the GODDAM code to get the radio / CD to work again!!!!)

Loose rivets
24th Jun 2016, 00:26
Lots of cars, from my Cadillac to my little BMW, have a way of getting into the codes by pressing something. Something like the miles reset - but while you're tuning the ignition on. Press and hold for 5 seconds, to do this, and stand on your head while pressing that, for something else. One can also reset the oil service light etc.

Sue Vêtements
24th Jun 2016, 02:41
Beware the flashing CEL

If the thing comes on solid, you can probably ignore it ... at least until you get home

but if it flashes, you should stop immediately ... even if you're in the fast lane with a semi up your arse

ask me how I know :(

and CEL = Check Engine Light

and over here you can got to Auto Zone (who sell parts) and they'll read the CEL for free, and why not? you'll probably end up buying an O2 sensor ... ask me how I know :(

24th Jun 2016, 02:43
My question related to the ability of cars to now have these big screens on the dash that can do all sorts of things - phone - email- texts - internet - movies - radio - forward camera - rear camera - radio telescope - microwave blaster - image of your living room in real time .......
If they can do all these things, why can they not display, in plain language, the detailed fault. Don't want codes - don't want to go to Walmart for a gizmo - don't want to download an app for the phone - don't want to have to consult a manual to decipher codes --- Just tell us what the damn problem is.


24th Jun 2016, 06:04
If they told you in plain language what was wrong, you wouldn't have to go to a dealer and pay them to tell you.

24th Jun 2016, 11:23
Computerised electronics are only as smart as their programming and sensor's fidelity allows.

simon brown
24th Jun 2016, 11:41
Typical first morning post Brexit and the bloody dpf light on the Citroen goes on...more Eloys fluid for the DPF me thinks

24th Jun 2016, 17:27
My mechanic used to say "Give it a good frashing". One was advised to do exactly that only last week by one's Motor Fettler. (Didn't work :()

What we used to call an "Italian Tune-up". :ok:

24th Jun 2016, 22:07
There was a lot to be said for the Mk 2 Cortina! Except the rust on the bodywork at the top of the front shock absorbers.

24th Jun 2016, 22:22
There was a lot to be said for the Mk 2 Cortina! Except the rust on the bodywork at the top of the front shock absorbers.
Actually, one remembers saying quite a lot about the rust at the top of the front shock absorbers...

24th Jun 2016, 22:37
Mike's been on for 40k miles, every so often one of the O2 sensors coughs and throws a code that puts the light on. Problem is you can't clear said code without a proper diagnostic, minimum £20, and it'll probably do it again, so not worth faffing with. My mechanic mate's comment was "If it's not using more petrol don't bother". It doesn't.
If it flashes though sort it quick as misfires can kill the catalyst which is both an MOT fail and expensive. On my Vauxhall it means the coil pack is duffed, £70-100, does it about every 2 years. Easy fix but bloody annoying.

Windy Militant
24th Jun 2016, 23:58
If they can do all these things, why can they not display, in plain language
Be careful what you ask for you might just get it!
Imagine turing the ignition in the morning and getting this.

Car:"Do you want me to sit in a corner and rust, or just fall apart where I’m Parked?”

Car: “And then of course I’ve got this terrible pain in all the diodes down my left side.”
Meadowrun: “Is that so?”
Car: “Oh yes. I mean I’ve asked for them to be replaced, but no one ever listens.”
Meadowrun: “I can imagine”

Car:“Let’s build cars with Genuine People Personalities,’ they said. So they tried it out with me. I’m a personality prototype. You can tell, can’t you?”*

*Blatently pinched from the Hitch Hikers Guide to the Galaxy with thanks to Marvin the Paranoid Android and Douglas Adams. ;)

25th Jun 2016, 00:12
Wouldn't be a C5 would it? I have one of those and the first time I saw the DPF moan coincided with my putting the car in to a Citroen expert to have steering pipes replaced. I asked him if he could top up the fluid bag and his response was "No bloody way. Far too fiddly and messy". Smashing. Every now and then I throw a capful of Eloys (or is it PAT?) in with the fuel. It doesn't do anything for the DPF warning light but it makes me feel a bit more comfortable. I have come to the conclusion that Citroen electronics are the planet's worst! Some times, the driver's window refuses to close. It goes so far, changes its mind and comes back down again. Occasionally, if I switch on the windscreen wipers, the driver's window takes that as its cue to open. If I make a left turn at around the same time, the window closes again. On a couple of occasions I have been unable to switch off the radio. The only cure for that is near voodoo ritual of switching on the ignition, pressing something (can't remember what now), removing the battery positive connection, counting to 10, reconnecting the battery and switching something else on and off from outside the car. That does it! Recently, I noticed the service light was not on and there was no DPF fault warning. Worried me a bit but the next time I started the car, it was back again, giving me a nice warm reassuring feeling. A good car for all that though.

25th Jun 2016, 01:44
That's the ffrench.
"This one for export to the Anglais, Pierre? Good, let's mess with the electronics, code neuf."

25th Jun 2016, 04:35
A few things you can do.
Most are caused by oxygen sensors before or after the catalytic converter and are very expensive to replace 4 of them.
Clear the codes as we do in the USA.
Disconnect the battery and then reconnect after a min or so.In the USA go to to advance auto parts or orielly they have a code reader for free and will tell you what code are flashing expecting you to buy the parts to correct.
Now once you determine oxygen sensor, buy the old day no fouler s for the spark pugs.
Remember we used them years before to prevent plug fouling in old engines.
Put 2 of these together, one will have to be drilled out to make room for the oxygen sensor tip.
This will place the oxygen sensor far beyond the reading capability.
No more check engine light and always pass inspection.
Some have even found a way to take the oxygen sensors out the loop or system computer.
These oxygen sensors fail often, too expensive to keep replacing them.
The correct way does not work.
Use your conscience here.
I sleep well at night doing this.

27th Jun 2016, 13:06
16 years from new and the check engine light has never come on (other than when turning the key in the ignition before starting).

Having driven a fair share of fleet cars that exhibit the usual gremlins I think I got lucky with this one.

Trouble is the whole car is only worth the cost of a replacement module.

Fingers remaining firmly crossed.

Loose rivets
27th Jun 2016, 22:55
A long sigh.

http://img.photobucket.com/albums/v703/walnaze/Cars/img004.jpg (http://smg.photobucket.com/user/walnaze/media/Cars/img004.jpg.html)

27th Jun 2016, 23:30
A Sunbeam and a Sunshine Yellow 2CV.

29th Jun 2016, 15:05
An excellent time-warp painting,but I don`t see his mug-of-tea,unless `the lad` is away making it....

29th Jun 2016, 15:19
Windy, The wifes old Saab 95 has been doing that since new. [T Reg]. Bing Bong Break light failure. Reset. All ok. According to Saab there only has to be a diference of 30mV between the rear brake lights for this to occur. So what is measuring this in the Dice Twice Thrice computer- I`m buggered if I know. Think there must be a little man in there with a millivoltmeter.

29th Jun 2016, 17:30
Same here with my SAAB 95, it's good to know I'm not alone.

29th Jun 2016, 19:32
I had a Renault Scenic for a few years which was remarkably reliable. It did have one weird electrical fault which I never managed to sort out (never willing to buy a replacement ECU...). If I switched the ignition on, even if I didn't need to start the engine (e.g. to close a window), I had to start it up and run the engine for a minimum of 2 minutes. If I didn't do this, the next time started the car, the "throttle potentiometer" light would illuminate and The engine speed would not respond to the throttle pedal at all. It would sit there at 2000rpm for two minutes, then would start 'hunting' between 1000-2000rpm. At this point I could switch the engine off. Restarting immediately the fault would have disappeared and the car would drive normally. There was never a problem when driving, if it started normally. I had the throttle potentiometer and throttle body replaced by Renault, but it still did it.
It seemed random at first, but once I'd figured out the two-minute thing (which took many months to ascertain) I just managed the problem by always making sure the engine ran for at least the required time.
It eventually got traded in as a part-ex on my current car.

simon brown
29th Jun 2016, 21:36

Yes a 2009 mk2....too bloody complex by far
Make sure its got a strong battery.Ive been told by the specialist i take it to,that as im doing big mileages between fillups its not getting the squirt of fluid as often so the d p f dries up....just open the cap once a day now and it doesnt happen cant really grumble in the 98k miles ive done in it its only needed consumables and an ABS speed sensor so i guess i must be lucky

Loose rivets
29th Jun 2016, 22:30
Hello, sycamore

but I don`t see his mug-of-tea,unless `the lad` is away making it....

I rather imagined coffee, or a glass of vino especially as the Sunbeam has no front number plate.

This is, or was, mine. I'll show it again as I have no shame.

http://img.photobucket.com/albums/v703/walnaze/Cars/bikes/DashboardHRobonSunbeamS7.jpg (http://smg.photobucket.com/user/walnaze/media/Cars/bikes/DashboardHRobonSunbeamS7.jpg.html)

29th Jun 2016, 22:36
The 2 CV, despite its registration, seems to be left drive - and the person in overalls looks female to my eyes.

Loose rivets
30th Jun 2016, 00:29
Hee hee, that reminds me of the young person in the filling station at Walton on the Naze.

(It was around 1960 and I had an Oldsmobile 88* which swept onto the forecourt with its tail in the air, and when full, was lowered with fuel weight as though ready to pounce.)

Anyway, the young person was white-coated, tall, with a bob of shiny black hair. I had an immediate attraction to this person, but was not totally, not absolutely, not a million % sure they were female. My reputation in the town was at stake.

Bob. Now there's a name to conjure up the right image.

Hello, Bob. You look like a fine fella-me-lad. Slap, (in a manly kind of way) How's about fillin' her up? Slap.

I never found out - despite a heart-pounding attraction.

*176 quid from a dealer near Tower Bridge. Still had Washington plates.

Back to mysterious automation. A pal and I were looking at the 4 barrel carb with the engine ticking over. Suddenly the 6 ltr V8 revved up and went back to tickover. It did it again. I said, Let's stand back an look at it. Funny kind of thing to say, but we often laugh about it. It did it again.

The sunlight was shining on the wind-shield and opaque with the reflection of Elm trees. The engine revved again. At last I ran and flung the door open. Another mate - with a huge grin on his face - had slipped silently into the seat.