Technical Bad earth & poor starting

[IanWard]

Hi all, my daughter has a 2009 500 sport 1.2, which up until a few days ago has been faultless, started at first turn of the key, I got a call to say my car wont start its just dead, when I had a look I thought she'd just left the interior light on and battery had gone flat, so bump started the car and all seemed fine...

left it running 10 mins, turned off and attempted to start again - same again, this time accompanies by a whole series of fuel cut off and ABS warnings, bumped again and took for a 10 min drive - same again.

After checking all the fuses and starting to search common faults, and came across the issue with the body to gearbox earth strap, tested by putting a jump lead from engine to battery negative - all the warnings went away and car cranked and started eventually.

have replaced the earth strap with a heavy duty earth cable, and the car now cranks much better, but starting takes 5-10 seconds. I've gone through and checked the plugs - all in good condition, other than not being tight and unscrewing 2 of them without a ratchet.

I've now gone through checking for any other bad earths and all seems ok - but the car is a real pain to start again anywhere between 5 and 10 seconds of cranking before it finally fires up. Has anyone else experienced anything similar? the only other thing that i appear to have found whilst searching is the car may need a software reflash - could this have become corrupt with bad earth?

EDIT: I have hooked it up to a Snap On code reader, nothing really obvious just 2 faults ABS: C1215 Brake Switch and Body Computer B1010 Brake Switch, none of which i would expect to give the starting issue

 

[John202020]

Try disconnecting the battery,have a coffee and re try? When starting pause between ignition on and cranking?
Let us know if any difference

 

[IanWard]

Hi John, Thanks for the reply - I have tried that, took the battery and tray out completely this afternoon to remove the broken braided earth strap. didn't appear to make any difference. I did pause between ignition on and cranking to allow the fuel pump to pressurise.

 

[IanWard]

So the plot thickens... she has now come home, engine light on, rescanned and new codes:

Engine Management:
P0504 - Brake Pedal
P0335 - RPM Sensor

Body Computer:
U1733 - Convergence Telematic Node L1 and L2
B1010 - Brake switch (had this one first time)

The issue appears to be progressively getting worse, but I have a feeling ?module issue - if the earth strap failed and has earthed through other routes has it done some damage?

I have read elsewhere on the forum about undertaking a Proxi Alignment procedure - the reader I have borrowed does have the ability to do this, but didnt want to go doing things without understanding fully what the purpose is. If there is anyone who can offer advice or point me in the right direction?

 

[varesecrazy]

Has the car had any work done recently..?

When was the cambelt and waterpump changed last?

 

[IanWard]

Hi varesecrazy,

No work done has been done recently, we've had the car 12 months now and its been brilliant so far. Cambelt will be due shortly as has around 70k on the clock now.

It was strange - worked perfectly, parked up for the night and bam - wouldn't crank, and then as described in first post.

 

[varesecrazy]

Is the fuel pump definitely running reliably?

 

[IanWard]

Interesting, my brother said it sounds like low fuel pressure, and also found another post on here referencing the 'U1733 - Convergence Telematic Node L1 and L2' with low fuel pressure.

You can hear the pump prime with ignition on, will have a look tomorrow to see if I can get a live data readout on pressure.

however when the car does eventually fire up - it drives like normal. have said not to use the car for the time being as not sure if it will do any damage.

 

[chris3234]

Does the blue and my system work?

These are known to drain the battery if they fail

 

[IanWard]

Hi Chris,

The Blue and Me has never really worked that well, but doesn't now as we have an aux lead plugged into the back of the stereo. The battery is actually ok - was just the initial symptom of not cranking that I thought was the battery, but with earth strap replaced its good. It certainly gets tested with the long cranking to start.

 

[IanWard]

I've just cleared the codes, started up and the check engine light remained on the dash, checked the fault code and got RPM sensor again.
Once it has started the RPMs are shown pretty close to the target value and update on live view.

I guess this could be one of the reasons its not firing if it doesn't know how fast its turning? although, when it does start seems to idle just fine.

 

[IanWard]

Screenshots below

 

[mj2k]

Sounds to me like you need a new battery, random errors are common on all cars if the battery's been completely drained and a cell got damaged in the process (or if it's just died of old age); once the battery's damaged there simply won't be enough power available to run all the systems, even if it is displaying 13.8v across the terminals when disconnected.

I had similar on a Citroen Xsara VTS years ago - headlights got left on, battery completely drained, recharged the battery and all seemed well, except for mad, random errors coming up and intermittent non-start. Replaced the battery, reset the ecu, and (ab)normal service was resumed

 

[IanWard]

Hi Mj2k,

Thanks for suggestion - The battery is ok, it wasn’t dead - just a bad earth not allowing the car to crank. Battery is only 12-18m old.

 

[mj2k]

Hi Mj2k,

Thanks for suggestion - The battery is ok, it wasn’t dead - just a bad earth not allowing the car to crank. Battery is only 12-18m old.

Might be worth a try anyway if you have a spare battery, better to try the simple things first before assuming the loom or ecu are goosed

Edit: Oh, and check the continuity of the battery->earth cable, and positive cable, and try that proxy alignment thing you mentioned. Judging by the range of different / random issue you're getting it's not worth replacing sensors at this stage, since it sounds like something else is preventing CAN bus comms and replacing the sensors might well do nothing.

 

[John202020]

Hi Mj2k,

Thanks for suggestion - The battery is ok, it wasn’t dead - just a bad earth not allowing the car to crank. Battery is only 12-18m old.

New battery about £45 it's quite possible the bad earth over the last year or so has compromised the battery, I think it's still worth changing I bought a Varta version.

 

[IanWard]

Changed the battery for a known good one, and still get the same issues, spent a couple of hours last night going through everything I have found on the forums - and that starter motor is a pain in the **** to get at, anyway bolts tight and cables looked good. tried the Proxy Alignment - all modules were configured, so just followed the instructions around power off, wait - power on etc...

The intermittent fault that keeps coming is the RPM sensor, which i believe is the crank sensor - I found a good page that shows how to test the sensor with a multimeter on both AC voltage and resistance, and need to check the state of cables. I don't want to get exited, but am hoping i may be getting closer to the poor starting - if the engine doesn't know where it is, maybe not adding fuel and a spark? although on that logic when it does eventually start why does it run ok? - ill test give a good clean in the area and see how I get on, failing that I may have to concede and get it into an auto electrician.

 

[John202020]

This might sound odd, disconnect the Lambda sensor and try starting, yes the engine light will be on but the car will follow the fall back map? The ecu will generally run a richer mixture?

 

[jackwhoo]

Changed the battery for a known good one, and still get the same issues, spent a couple of hours last night going through everything I have found on the forums - and that starter motor is a pain in the **** to get at, anyway bolts tight and cables looked good. tried the Proxy Alignment - all modules were configured, so just followed the instructions around power off, wait - power on etc...

The intermittent fault that keeps coming is the RPM sensor, which i believe is the crank sensor - I found a good page that shows how to test the sensor with a multimeter on both AC voltage and resistance, and need to check the state of cables. I don't want to get exited, but am hoping i may be getting closer to the poor starting - if the engine doesn't know where it is, maybe not adding fuel and a spark? although on that logic when it does eventually start why does it run ok? - ill test give a good clean in the area and see how I get on, failing that I may have to concede and get it into an auto electrician.

It is rare indeed to get an rpm sensor fault code do not ignor it. Yes the rpm sensor is also the crank position sensor if it is not functioning correctly the ecu wont "know" the crank is rotating or crank position so wont inject fuel or trigger ignition.
It is a cheap sensor maybe just check the sensor wiring for obvious damage then fit new sensor. After fitting new rpm sensor you will almost certainly need to do a "phonic wheel relearn"

Good work so far.

Good luck

Jack

 

[IanWard]

Hi Jack,

I followed the guide on https://www.700r4transmissionhq.com/p0335-fiat-500/ and the link to doityourself on testing the crank sensor.

I wasn't comfortable pulling back the cable to get probes on the back for fear of damaging the plug/cable to do the AC test whilst running, but removed the sensor and checked resistance, should be 1100 was 1168 not sure if that is within normal limits or not.

The cable is in a protective split sleeve but didn't look damaged on visual inspection, I'll order a new sensor and try it - will have to borrow the diagnostic computer again to do relearn procedure.