Technical Random (flickering) Check engine light

[ZaphodB]

Hi folks, had a weird one today (and a few days ago)

Out of the blue the check engine light will flicker and 'check engine' will also randomly flicker on......

It was (is) hot today 28 degrees , and I seem to recall the other day it happened it was hot.....

Today I was waiting in traffic when it first started, (it was only a short drive to the post delivery depot), appeared to clear as traffic got moving again, no loss of performance to speak about.

Then 1/2 a mile later I'm stuck at a red light for30-45 seconds or so behind a car, and it came up again , just as the lights were changing !! , he moved off and the engine stopped just as I was about to clutch and engage 1st !!!...

Restarted ok, and I drove a further 1/2 mile to my destination without a problem....

and it was AOK as I went back to work (about 4 miles)

A bit puzzling .... I was thinking it's extreme heat and sitting there idling , where something just goes over a temperature threshold....


I read somewhere if it's flickering it's ignition related/coil pack/spark plug ? or maybe it's a crank sensor ?

Nothing shows up on MultiECU as a stored fault, which is frustrating....

Any pointers?

 

[bugsymike]

Hi folks, had a weird one today (and a few days ago)

Out of the blue the check engine light will flicker and 'check engine' will also randomly flicker on......

It was (is) hot today 28 degrees , and I seem to recall the other day it happened it was hot.....

Today I was waiting in traffic when it first started, (it was only a short drive to the post delivery depot), appeared to clear as traffic got moving again, no loss of performance to speak about.

Then 1/2 a mile later I'm stuck at a red light for30-45 seconds or so behind a car, and it came up again , just as the lights were changing !! , he moved off and the engine stopped just as I was about to clutch and engage 1st !!!...

Restarted ok, and I drove a further 1/2 mile to my destination without a problem....

and it was AOK as I went back to work (about 4 miles)

A bit puzzling .... I was thinking it's extreme heat and sitting there idling , where something just goes over a temperature threshold....


I read somewhere if it's flickering it's ignition related/coil pack/spark plug ? or maybe it's a crank sensor ?

Nothing shows up on MultiECU as a stored fault, which is frustrating....

Any pointers?

Nothing coming up as "intermittent" on your diagnostics?
For it to die, as you suspect certainly worth checking ignition side,.
Do you think next time you can see if rev counter stops instantly suggesting crank sensor, especially as heat related.
Other than that, a dry connection?
Always annoying when issue not happening when you want to test it.

 

[ZaphodB]

Because it eventually cut out earlier today, I don't believe it's a coil pack (because surely it would just run a a bit rough )

I'm thinking crank sensor, because that surely would cause complete engine stop ... I've just had it on MultiECUScan whilst idling and it eventually (after engine had warmed up to normal temps) flashed the 'check engine' and flashed he engine light at the same time a few times.

But it never stopped this time, I was monitoring various things on MES and nothing stood out .....

Maybe MES can't see basic obd codes?, it's a bit unclear to be honest which ECU to choose (but I've worked out I don't use the yellow adaptor when interrogating the ECU (but yellow adaptor is used for every other module)

I'm surprised it's not logging a fault to be honest , I might speak to MES tomorrow just to make sure I'm right in not using the yellow adaptor for talking specifically to the engine ECU

 

[bugsymike]

Because it eventually cut out earlier today, I don't believe it's a coil pack (because surely it would just run a a bit rough )

I'm thinking crank sensor, because that surely would cause complete engine stop ... I've just had it on MultiECUScan whilst idling and it eventually (after engine had warmed up to normal temps) flashed the 'check engine' and flashed he engine light at the same time a few times.

But it never stopped this time, I was monitoring various things on MES and nothing stood out .....

Maybe MES can't see basic obd codes?, it's a bit unclear to be honest which ECU to choose (but I've worked out I don't use the yellow adaptor when interrogating the ECU (but yellow adaptor is used for every other module)

I'm surprised it's not logging a fault to be honest , I might speak to MES tomorrow just to make sure I'm right in not using the yellow adaptor for talking specifically to the engine ECU

Sorry I can't advise on MES as I use MaxiEcu scan tool or my mates Snap On Zeus professional one.
I would have thought MES would have no problem doing basic OBD stuff as well as Fiat Specific, I know my MaxiEcu does.
The Crank sensor failures I have been involved with were usually with a warm engine and would die completely, cool down for ten minutes then happily start up as though nothing wrong, but I have heard others say different.
Apart from running the engine and touching various wiring connectors etc. to see if you can encourage a breakdown.

 

[ZaphodB]

I've ordered a crank sensor first on a whim.... and the fact that a genuine brand new Bosch is only £18 currently delivered.

We'll see if that helps , I'll report back

 

[ZaphodB]

It did it again (flickering engine light and 'check engine') .... only when idling , another 28 degree day

I'm convinced the problem will disappear when the the temps drop

 

[bugsymike]

It did it again (flickering engine light and 'check engine') .... only when idling , another 28 degree day

I'm convinced the problem will disappear when the the temps drop

Sure it is not oil pressure?

 

[ZaphodB]

That wouldn't make it stall and stop (which it's only done once ), and it wouldn't bring up check engine.

I can see where you might think along those lines but To be clear when the flickering does occur , it's not a constant flicker , it's just a random thing.

On way home today when it started flickering (at traffic lights and stuff), I just raised the revs a little and it cleared

Going out right now to check levels and see is MES has a live oil pressure reading

If I can be bothered I'll see if I can record the screen when it does it, still hot out there so likely it'll happen after a a bit of a warm up.

Besides if it was oil pressure it'd be flickering consistently

 

[bugsymike]

That wouldn't make it stall and stop (which it's only done once ), and it wouldn't bring up check engine.

I can see where you might think along those lines but To be clear when the flickering does occur , it's not a constant flicker , it's just a random thing.

On way home today when it started flickering (at traffic lights and stuff), I just raised the revs a little and it cleared

Going out right now to check levels and see is MES has a live oil pressure reading

If I can be bothered I'll see if I can record the screen when it does it, still hot out there so likely it'll happen after a a bit of a warm up.

Fair enough, just something we used to get on Ford Anglia's in the 1970s.
You never know what is going to bring up a warning these days. Some years ago my accountant had a grey import Lexus Saurer 400 that had an error message in Japanese on the dash, he paid a Japanese student to tell him, it was screen washer fluid low!

 

[ZaphodB]

So 30 minutes sitting in a hot car brought me a few things.....

I'd cleared all codes a few days ago (successfully), tonight when I scanned it , several modules reported a similar code.

BCM reported U0019-88
Airbag module reported U0019-88
Dashboard module reported U0019-88
Climate Control reported U0019-88
Parking sensor reported U0019-88

U0019-88 = B-CAN Line - Bus off

I'm not sure if it's a red herring due to the limitations of MES (or MES generally) or an actual fault. (I've obviously no other Abarth to compare it to)

I was mostly able to trigger the flickering check engine message and light, by a quick blip on the throttle after idling and letting the engine settle down to idle again.

 

[bugsymike]

So 30 minutes sitting in a hot car brought me a few things.....

I'd cleared all codes a few days ago (successfully), tonight when I scanned it , several modules reported a similar code.

BCM reported U0019-88
Airbag module reported U0019-88
Dashboard module reported U0019-88
Climate Control reported U0019-88
Parking sensor reported U0019-88

U0019-88 = B-CAN Line - Bus off

I'm not sure if it's a red herring due to the limitations of MES (or MES generally) or an actual fault. (I've obviously no other Abarth to compare it to)

I was mostly able to trigger the flickering check engine message and light, by a quick blip on the throttle after idling and letting the engine settle down to idle again.

Can you do a "proxi alignment " with your diagnostics to show what is not connected.
It may be something as simple as with battery disconnected clean the BCM connector with switch cleaner and reassemble.
Another thing is using a "break out box" you can test for reading via the EOBD port giving lives and earths for ECUs and allows you to test the can bus etc. You will need to read up about it before testing though. I have used mine, but I am forgetting a lot of it.

 

[ZaphodB]

Never done a Proxi Alignment on this car, so I'll have to read up about it.

I've heard some scare stories about PA , so I'm a bit wary... but I can check some stuff tomorrow....

I've just been trawling the internet and found this:

U0019 C019 Solucion averia FIAT Bus CAN

U0019 C019 Solucion averia FIAT Bus CAN

www.autoxuga.com

which suggests it's a temperature related thing in the ECM amongst a slew of other stuff.

Full disclosure: I did have a boot lid actuator not operating a few weeks ago, turned it was the main feed to the actuator (or the ground to it), anyway one of the thick wires that feed the boot actuator.
All the other cables appeared ok, so I only repaired the clearly broken thick one to the actuator.
I wonder if some of the many finer cables in this boot loom could be damaged and causing (or contributing to) the issue ?

 

[bugsymike]

Never done a Proxi Alignment on this car, so I'll have to read up about it.

I've heard some scare stories about PA , so I'm a bit wary... but I can check some stuff tomorrow....

I've just been trawling the internet and found this:

U0019 C019 Solucion averia FIAT Bus CAN

U0019 C019 Solucion averia FIAT Bus CAN

www.autoxuga.com

which suggests it's a temperature related thing in the ECM amongst a slew of other stuff

Try the switch cleaner on the BCM connections first.
Definitely read up before the other side and always back up data if possible.

 

[Mike1alike]

Isn't that a voltage problem? Like bad alternator or bad ground cable or something wrong with the battery? And there is a voltage drop when you let it idling, like RPM dropping. Faulty alternator would act bad while getting hot. So do monitor the battery voltage. Would be good to read it in MES as well as direct on battery terminals with a multimeter.

 

[ZaphodB]

Battery appears fine, cranks perfectly well, starts on the button, when running it was showing up at 13.9v
It is the original , so not that old, both terminals are secure.

I've got a Plan B when it does occur , just raise the revs a little whilst standing at lights etc, this keeps the light away (if indeed it's coming on)
(I repeat it doesn't come on all the time during idle, just extremely randomly after idling for a while (at lights for instance)

I'm still hoping it'll all just go away when the heat dies down , cos so far it's only happened on these REALLY hot days (and once I think on the last heat wave a week or so ago)
But I will be doing a few more checks tomorrow to try and get a handle on what's occurring ....

One more snippet I spotted was I was monitoring pre and post lambda signal levels, during idle:

Just instantaneous values when I took the screenshot pic (they obviously varied slightly around these values)

Pre-cat Lambda 0.81V
Post-cat Lambda 1.53V
Pre-cat Lambda Integrator 0.99V
Lambda Pre-cat Status Closed Loop
Lambda Post-cat Status Open Loop

 

[Mike1alike]

Just instantaneous values when I took the screenshot pic (they obviously varied slightly around these values)

Pre-cat Lambda 0.81V
Post-cat Lambda 1.53V
Pre-cat Lambda Integrator 0.99V
Lambda Pre-cat Status Closed Loop
Lambda Post-cat Status Open Loop

Those are good values but for O2 sensors voltage you need to record a graphic, to see the oscillations, how they go.

 

[ZaphodB]

I've only just done a quick test , ran it up to full op temp, didn't flicker at all this evening......

I did record some (hopefully) pertinent measurements though.....

Pre-cat sensor seems fairly normal: oscillating from 0.2v to 0.8 (see attached video), post cat seems settled and steady.

Also of note: I notice knock sensor values are higher on a couple of cylinders (there can only be one knock sensor that I know about so not sure how it's calculating this .......

I was getting like (as a snapshot):

Cylinder 1 - 1318mV
Cylinder 2 - 2187mV
Cylinder 3 - 2055mV
Cylinder 4 - 1279mV

Central cylinders elevated - maybe that's just the location of the knock sensor that's bringing that deviation up......

But I repeat: engine light didn't come on/flicker during a 15 minute run at idle this evening (not moved since yesterday's check), engine was fully up to temp within a short while (not surprising given the ambient)

 

[Mike1alike]

About graphic, when you do them have full graph stopped on full screen and take a snapshot of the screen ("Print screen" button then paste in "Paint" and "save as..." jpeg.
The after cat O2 sensor voltage is way out of order on yours, much too high.

 

[ZaphodB]

I'll do just a Lambda (pre and post) graph some time tomorrow and report back.

 

[ZaphodB]

Top Post-cat
Bottom Pre-cat

This guy had the exact overly high reading of 1.6v same reading and it turned out to just a duff post cat sensor


Now I've just gotta work out the correct part number , bizarrely they list different ones for the manual gearbox and the robotised one ?!?

I prefer Bosch