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Technical Strange ODB-2 and ESP problem

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Technical Strange ODB-2 and ESP problem

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hitherematey

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Hi, as some of you may know I've been having problems with the ESP/hill holder on my Punto mk2b 1.8

Just to recap, whenever the temp outside drops below 6c I get a ESP/hill holder warning. I have stress tested the battery and alternator and all is fine and whenever I get this warning the aircon fails to start until later on.

So anyways I brought a ODB fault reader to try and shed some light but found nothing however, when I plugged the unit in I get the steering light, and the ABS, ESP and warning triangle flash together every few seconds. Sometimes the LCD display flashed too. Soon as I unplug it everything goes back to normal?

Sorry for the long post but I'm at a loss :bang:
 
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I've got a 1.9HGT mk2b Multijet with the same system and i will be honest i've never seen a problem with the system (at below 6c) and can confirm that its not just something the system does at low temperature.

as the ASR, Hill hold and ABS are all integral to one another, it does make me wonder if it is something silly like a ABS wheel Sensor failing at low temp or even the metal in the multi plugs being cold an loosing contact.

as its pretty difficult to replicate at the moment my only suggestion would be to give all the multi plugs on the ABS system a good clean make sure they are nice and tight, then wait for the cold weather to strike.

as for diagnostics what fault reader have you got? I think the standard cheap jobbies will only read the Engine ECU and not the ABS ECU so you might need to invest in Fiat Scan and a bundle of cables
 
Hi, thanks for your quick response. It's only the ESP/hill holder warning that comes on below 6c, the ABS still works.

If the aircon compressor activates when I start the engine I dont get any warnings at all?

I have a cheap RAC fault reader so only very basic, but I'm concerned about all the other lights coming on and flashing when I connect the unit. The code reader seems to connect ok but could this be a sign of a dodgy body ECU?
 
i don't think so i think its more likely to be down to the fault reader, causing it to flash what messages do you get on the dash multifunction display? or do you just get a simple "Hill Hold Failure" warning?

The engine ECU is separate to the ABS/ASC computer as is the body computer. so i'm pretty sure your cheep RAC scanner can't access it.

looking back at your original post.
when you say "whenever I get this warning the aircon fails to start until later on." is this only happening on start up?

if you stopped the car and restarted it after a short distance of driving does the fault/light go away?
 
When I plug the RAC unit in, the steering light comes on with the relevent warning message. The hill holder, the warning triangle and the ABS light flash on and off together. Sometimes the entire LCD display flashes too.

When I put the ignition on only I don't get any warnings (below 6c) but as soon as I start the engine it appears.

Occasionally after a short journey, when I restart, the light will go out but depends on how cold it is but it does seem quite random. What outside temp does the aircon compressor deactivate as I believe this is somehow related?
 
--- UPDATE ---

Messing around with my RAC reader today and it's now showing a code:

P1531 a/c compressor relay

Any ideas what this could be? The aircon has recently been serviced so should be topped up etc. I believe this could be a answer to my ESP troubles
 
Off the top of my head there is usually a relay that switches out the Aircon at high pressure, (which in cold weather is achieved quicker) should be in the engine bay fuse box but I have no idea which one
 
Ok, i swapped the T5 relay with equal one from the fusebox and it's made no difference. One thing I did find though is when its removed, the ESP etc light always comes on everything time so it's definitely related but that's all I know so far?

Is there any other checks or test I could do it's it's driving me crazy!
 
AndyRKett said:
Take relay out of car shove in freezer for an hour or two, put back in car and see if you can replicate the fault?
Click to expand...

I swapped the relay with the one next to it, just in case it was faulty but I still get the same problems. What temp does the a/c cut out (frost protection) or where is the sensor to it?
 
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The air con doesn't cut out with temperature that's not how air con works, it is all based on pressure differentials in the system however that doesn't mean you ecu isn't switching it on and off for some unknown reason
 
Sorry I should of been clearer in my last post. What I ment is when the exterior temp drops below a certain level, doesnt the a/c switch off to prevent damage to the system?
 
No there is nothing that can get damaged air conditioning a self limiting system by design

You can get ice buildup on the evaporator but When it does the pressures change stoping the ice from building further
 
Ok thanks for the replies. The other nights when it's was between -7c and -8c I noticed for the first time the a/c symbol had gone off regardless of what I set it too but strangely I had no ESP light.

Soon as the exterior temperature was around -1c the a/c symbol had returned (but no a/c) and shortly after the ESP fault returned.

By the way I have fitted a new,more powerful battery too but too no avail :bang:
 
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