General 500 fault code.

[J500dr]

I have purchased an 09 plate 1.2 with 42000 miles on it, it had a fault code after less than 24 hours of ownership. The code is p0641. I know this relates to a voltage issue of less than 5 volts across a sensor. The battery and alternator have been tested and are fine.
I approached the seller who told me he’d just replaced the potentiometer and pedal as it had a fault code on it. I think I’ve been had over and he’s sold it with a known fault but my mechanic says the pedal is new and suspects the seller was fault finding then gave up and sold it to me. It drives normally then without warning it won’t go over 2-3mph. You can sometimes reset it by turning it off and on and it may go back to normal but not always. My mechanic best guessed the issue to the throttle body but a new one hasn’t cured it.
Any ideas greatly appreciated

 

[varesecrazy]

Hi.and welcome.

Strange how so many parts have been changed.. with no fix

Any idea what kit your mechanic used?

MultiECUScan software is Fiatgroup specific..and tends to give more accurate results.

Many are VAG ( VW ) specific.. which won't help.

Shame your car is too early for start-stop

As that would confirm:deny any battery..or alternator issues.

In the meantime.. I Searched the forum for the P0641:

https://www.fiatforum.com/500/290615-500-multijet-fault-code.html

Charlie

 

[jrkitching]

Hello and welcome to the forum

Any ideas greatly appreciated

Use a Fiat-specific diagnostic tool to try to shed more light on what the issue actually is.

Given the history, taking this to a general purpose independent garage is unlikely to achieve much more than spending more money to not solve the root cause of the problem.

You basically have three good options:

1) If you're handy with spanners, buy a licenced copy of multiecuscan and an interface cable and see what additional information a purpose designed scanning tool throws up

2) take it to an independent Fiat specialist. If you're in or near to Hampshire, try this one. If you're not, try to find somewhere similar.

3) take it to a franchised dealer. This will likely be more expensive and on an '09 plate car, they're may try to sell you a replacement vehicle rather than making any real effort to fix yours. Some main dealers regard 10yr old cars as end of life vehicles.

On most modern cars, continuing to replace parts in the hope that one of the replacements will fix the fault is generally not a good approach to problem solving.

 

[John202020]

Is the EML light on?
Whilst the pedal may have been changed don't forget the throttle body also has a actuator.
You need as said some Fiat specific code reading software this could pinpoint the "sensor", poor earthing is also an issue caused by corrosion of terminals/earth points, note that all 500's require a replacement engine earth strap, if it's not been replaced it will need one, about £3 on EBay.

 

[typecastboy]

I had a potentiometer fault on a 500 a couple of years ago. Changed the pedal and the throttle body, cleared the code and as soon as I drive away code came back and went into limp. Turned out it was a voltage in two feeds from the engine computer to the pedal and one of the two connections was .5v out and that threw up the fault. Bought a second hand engine computer for £60 and had it virginised for £150. All was then fixed.

MES did not find the fault and the garage I took it to tried many things and was a process of elimination.

 

[J500dr]

Many thanks everyone, I’ll look for a local independent with fiat specific diagnostics