Hi all, I have an 02 plate 2.4 abarth which wont start. I had it a few times where it would turn over but not fire and then after a few minutes it would. A friend checked on computer and said it was cam or crank sensor (i couldnt remember which) but the car started every time for next month so forgot about it. Then the fault returned. I replaced the crankshaft sensor and the car started straight away and ran all day long, but the next day the fault returned. The AA came and their computer said faults 0340 and 1653 were present, one of which was camshaft sensor which in his opinion would stop it firing. fuel is present but no ignition. So today i have the cam sensor replaced which unfortunately is behind belt pulleys so the belt comes off and has to be replaced, and the car still wont start and the fault codes are still the same. Does anyone have any ideas what else i can try before i have to get it towed to fiats please

Have you disconnected the battery for over half
and hour connect back up and try and start it.
If it starts warm it up and do a Phonic Wheel relearn.

If it doesn't start then check the belt timing is correct.
engine should have been locked in position top and
bottom end before removing the cam belt. If it wasn't
then timing may need setting up correctly again.

John

Thanks for reply John, I havent disconnected battery tonight since replacing the sensor, although it was disconnected before and made no difference. Will give it a go in the morning. What is a Phonic wheel relearn though??

Needs disconnecting for 30 min or more to clear the faults
and get the ECU looking for the sensors. See added about
timing as well.

Phonic Wheel Relearn (Courtesy Yellow Stilo)

start engine, wait until fan kicks in (engine temperature must be high to avoid damage)
rev the engine up to 6000 rpm (5000 is minimum but 6000 is better) and let engine restore idle speed
repeat another two times
key off
key on after 10 seconds - problem solved


if not solved - repeat procedure until blinking and beeping has stopped

You could do with the diagnostic equipment to recheck codes
may be the crank angle sensor causing problems, as I think the cam sensor
governs fuel and the crank sensor the spark.

John

Fingers crossed the disconnection will do the trick, and its nothing more serious like ecu or broken wire between plug and ecu. Will give it a go and let you know. Thanks again for replies

Well unfortunately the disconnection didnt work, i even touched the cables together as i was told this would clear the capacitors storing info for the memory, locked and unlocked doors but still no joy. Got an electrician coming now to check for broken wire between sensor and ecu

but what is the Phonic Wheel ?

Well the electrician has been and says there is power and earth from the ecu to the cam sensor plug but nothing coming back from it. He hooked it up to an oscilloscope and it just gave a flat reading, so in his diagnosis its a faulty sensor. Does anyone else have any other ideas on what else i can try please? And after clearing fault codes from memory the only one returning is the camshaft sensor circuit.
Sorry John, just reread the last bit of your message about crank sensor causing spark, maybe its possible that the fault lies in this circuit as the spark is the only thing i dont have, although computer says no problem. It does seem strange that after fitting crank sensor it worked for a day but not the next so there could be another underlying problem there. Maybe it will have to go to fiats for proper diagnosis

I have a 1.8 with variator and have had a few weeks
of intermitent faults with the cam sensor. The cam
wheel has 2 points of reference which as it rotates
caused flutuations in the magnetic field produced
by the cam sensor. I used the free software from
www.fiatecuscan.net and a £10 kkl cable off
ebay to clear the fault a number of times until
one night I ended up with a crankshaft and camshaft
error. I cleared both them and it's been ok since
then. I'd check that when the cam belt was
removed the crankshaft sensor hasn't moved
or got dirty and the plug is fitted tight.

Hows the electrician tested the sensor as
2 wires produce the magnetic field the third
measures the pulse.

John

Thanks again for reply John, on my car the crank sensor goes into the engine by the bulkhead so i dont think it would be disturbed by the cam belt being fitted, plus it wasnt starting before having it changed. It maybe worth a look to make sure its tight though and didnt work loose the first day.
The electrician hooked it up to laptop with probes and he said he probed the output wire which should have given a graph reading up and down as the wheel rotated through the sensor but it was just flat.(that is of course if he had the correct wire )
I did try disconnecting cam and crank sensors, and battery and reconnected hoping it may fool ecu into thinking new ones fitted again but no joy.
Am now awaiting AA once again who if cant sort it will tow me to fiats and then they can diagnose from there

Switch ignition on don't engage starter after
warning lights start going out engage starter
you may need to churn the engine over first
time to enable the sensors to register.

I disconected the battery and had fatal errors
on the sensors. I then cleaned the rust off
the lugs on the cam sensor with emery cloth.
there is one lug and then a larger area with
a square knotch out of it, disconected the battery
for 30mins and then it started up.

John

Had AA back again today and he hooked it up to computer
and live diagnostic showed no output from crank sensor,
when engine was turning over it was just 000 and according
to him it should show a reading as it turns.
Any way he towed car to fiats and they are going to check it
out as he thinks it could be ecu problem..... will let you know

Best of luck with it, hope it doesn't hit your pocket
too much. I'm thinking it may be the crankshaft sensor
either incorrect gap or the wiring or multi plugs going to it .
Top groove on the sensor ring obscured, or bad earths.

Makes me realise I was lucky getting mine up and running
again. It still doesn't like it if you stall the car and try to
restart too quickly throws a P0340 code. If I leave the
ignition off for 5-10 seconds before restarting it's ok,
bit difficult in traffic though.

John

Thanks for all your replies John, I hope it doesnt
cost too much more myself!! The crank sensor does
sound the most promising for wiring problems as i
dont think there is adjustment on it as it just bolts on
dissappears inside block, so if wheel is obscured its gonna
need engine apart to get to it..... If thats the case i think
there will be alot of abarth spares for sale on here

Will let you know what they come up with

ive same probs...thankyou....gonna start looking at wat u done...maybe i might
get mine running again:bang::bang: