Technical Can anyone help me understand a warning light issue?

[Diwedd]

Hello,

I have a 2007 Fiat Panda (Dynamic model - I think). It is used mainly for short trips, but every now on then I have to undertake much longer journeys. Typically, after about an hour the EOBD warning light

comes on. I have read the following about this light:

"This is the injection / EOBD warning light. If the light comes on while driving or stays on after ignition, it indicates the injection system is not working correctly. This is a malfunction in the fuel supply / ignition system and may result in excessive exhaust emissions. Other symptoms will include high fuel consumption, poor performance and vehicle not driving very well".

What I have noticed is that whenever the light comes on, the needle of the temperature gauge drops below the C mark. It sort of flat-lines. It then remains there until I pull over and rest the car for a bit. When I start driving again, the needle of the temperature gauge works fine again, but the EOBD light remains on. It is worth noting that the car doesn't seem to overheat when the needle flat-lines, or when it runs with the EOBD light on after resting.

This only happens on long journeys.

What I would like to know:

1) is there a connection between the EOBD light coming on and the temperature gauge needle flat-lining?
2) why does the needle work after a rest period but the EOBD light remains on?
3) whether the temperature gauge is actually still working when it flat-lines? As I said, the car doesn't seem to overheat and the red light indicating too much heat never comes on. However, if the temperature gauge isn't actually working when it flat-lines, then it could explain why the red light never comes on. To date, I have never seen steam coming from the engine, and the fan seems to kick in when needed.

Many thanks
D

 

[koalar]

The rest of the world knows the as an engine check light.

I would expect the thermostat rubber seal has perished

The ECU see it as a fault and puts the cooling fans on full dropping the temperature

This is only a guess until you read the engine fault code

From cold the radiators top hose should stay cold for a couple of minutes. If the thermostat rubber seal is missing it will start to warm up as soon as the car started

 

[portland_bill]

It is probably the temp gauge dropping first, that results in the light coming on later. (Later could be milliseconds)
The injection system needs to know the engine temp, as one of its inputs to determine the correct fuel quantity to inject. If the temp sensor lies, the fuel injected is wrong. Then the oxygen sensors in the exhaust detect incorrect fuelling, so argue with the injected fuel quantity. With the inputs disagreeing, the computer throws its hands up, and puts the light on.

I think there may be two temp sensors, not sure, not had to look closely at mine. (That'll jynx it) Best to get a diagnostic device attached to see what the computer reports.
Possibles:
Temp sensor faulty. Most likely.
Thermostat faulty. Less likely, as even if stat went fully open, after that time, engine would still be hot. I'd expect sensor to maybe drop to midway between cold and half, but not off the scale.
Wiring faulty. Less likely, as unusual to be temp or time related.
Coolant loss, or airlock. Less likely, as this should show all the time.
Connections at computer, or clocks. Hassle to check, so only if diagnostic suggests.
Main earth cable from battery to gearbox and car body. These corrode internally, and when failing cause all sorts of strange electrical issues. Needs checking, but I'd expect a more random failure.

 

[koalar]

It is probably the temp gauge dropping first, that results in the light coming on later. (Later could be milliseconds)
The injection system needs to know the engine temp, as one of its inputs to determine the correct fuel quantity to inject. If the temp sensor lies, the fuel injected is wrong. Then the oxygen sensors in the exhaust detect incorrect fuelling, so argue with the injected fuel quantity. With the inputs disagreeing, the computer throws its hands up, and puts the light on.

I think there may be two temp sensors, not sure, not had to look closely at mine. (That'll jynx it) Best to get a diagnostic device attached to see what the computer reports.
Possibles:
Temp sensor faulty. Most likely.
Thermostat faulty. Less likely, as even if stat went fully open, after that time, engine would still be hot. I'd expect sensor to maybe drop to midway between cold and half, but not off the scale.
Wiring faulty. Less likely, as unusual to be temp or time related.
Coolant loss, or airlock. Less likely, as this should show all the time.
Connections at computer, or clocks. Hassle to check, so only if diagnostic suggests.
Main earth cable from battery to gearbox and car body. These corrode internally, and when failing cause all sorts of strange electrical issues. Needs checking, but I'd expect a more random failure.

As the engine warm up and passes 60 degrees Celsius the ECU expect it not to ever fall below 60

If it does due to a faulty thermostat (mainly on long down hill stretches of motorway) it triggers a P0115 the engine check light comes on and the fans to come on fast permanently dropping the temperature gauge down. Very common fault.


There only one temperature sender on the 1.1 and 1.2

Until some diagnostic are preformed we will remain in the dark.

 

[Diwedd]

Thank you very much for the replies. I don't know anything about cars so I still feel a bit in the dark. I wanted to get a rough idea of what the problem might be before taking it to a garage. I don't want to be bamboozled and feel as if I have some information, I will be able to negotiate the issue in a better way.

 

[koalar]

Unfortunately the error light is generic

Without reading the code it could be anything

From cold

The radiator fans should not be on

If they are switch the engine on and off a few times the fault should self clear

start your car and put you hand on this hose it should stay cold for at least 3 minutes

It will confirm or eliminate one possibly within a few minutes

 

[Diwedd]

I thought I would give n update on this. I took the car to a garage and the guy did a scan with an ODBII scanner. It returned two error messages i.e.

• P0115
• P0204

However, the guy said that in spite of the error messages, the car seemed fine, so he cleaned out all the bits that could be cleaned. I guess I will know on my next long journey if all is in order.

 

[koalar]

Check the top hose as per the post above

Still sounds like the thermostat

P0115 is the error code you get normally

Let’s hope the injector circuitry was just a knocked wire while checking things out.

 

[The Panda Nut]

A thermostat is a cheapish thing £30 and 1 hour to fit at worst. They seem to be subject to failure on Pandas. The temerature sensor is in fact part of the thermostat so that would be replaced (on the 69hp versions at least) atthe same time. Just keep an eye on the water level as major water loss can lead to more expensive repairs being needed.

 

[koalar]

A thermostat is a cheapish thing £30 and 1 hour to fit at worst. They seem to be subject to failure on Pandas. The temerature sensor is in fact part of the thermostat so that would be replaced (on the 69hp versions at least) atthe same time. Just keep an eye on the water level as major water loss can lead to more expensive repairs being needed.

Unfortunately on this car 2007 the thermostat is on the right near the battery ( looking from the front ) and the sensor is right at the back

Testing for the common thermostat fault takes less than 2 minutes, as long as the engine is already cold

No tools or skills required

 

[The Panda Nut]

Unfortunately on this car 2007 the thermostat is on the right near the battery ( looking from the front ) and the sensor is right at the back

Testing for the common thermostat fault takes less than 2 minutes, as long as the engine is already cold

No tools or skills required

Its why I like Fiats. Like me. Older is better.

 

[rmjbn1]

As the engine warm up and passes 60 degrees Celsius the ECU expect it not to ever fall below 60

If it does due to a faulty thermostat (mainly on long down hill stretches of motorway) it triggers a P0115 the engine check light comes on and the fans to come on fast permanently dropping the temperature gauge down. Very common fault.

Fairly certain I've recently experienced just this.

Since we've had the car it never quite gets up to temperature, sits a little below the half way mark (closer to 3/8). So I suspected the thermostat of leaking a little due to perishing rubber. But that hose to the rad took a while to warm up, heater gets toasty, and it became one of those jobs I was going to get round to...

Early morning motorway run, long downhill (M62 off the moors), hit traffic, slowed right down.

Temperature gauge suddenly dropped below C, EML came on (with classic timing, the day before the MOT, having run faultlessly all year)

Pulled over, switched off, checked coolant level and for signs of leaks. All OK, set off again, temp gauge was low but slowly climbed back to 3/8.

Thankfully disconnecting the battery for an hour cleared the EML, and got a new MOT with no advisories

Just had a chance to connect to MultiECUScan, P0115 DTC, and shows recorded coolant temp as 60deg c

My fault for being too lazy to change the thermostat and coolant. Will get on with it.

 

[koalar]

Yep sounds like the same

Should have mentioned that P0115

Self clears after so many starts and stops without an error

Maybe 5 or 10 can’t remember now.

Just in time to get the heaters blowing hotter for winter.

 

[The Panda Nut]

Check the top hose as per the post above

Still sounds like the thermostat

P0115 is the error code you get normally

Let’s hope the injector circuitry was just a knocked wire while checking things out.

Yes I agree. The thermostat is easily and cheaply changed and worth doing if in any doubt. On later Pandas the temp sensor is integral to this. My experience of this B light, on the Panda and other types and sizes of car is they are far from good at telling you what is really the problem and sometimes its not what you expect. If its thermostat or temp sensor 1 hour should see it done plus c £40 for parts aty worst. With the second fault coide I would reset it and see what happens. One thing at a time. My suspicion is that mat be a large red herring related to the temperature being wrong. Best of Italian luck to you.

 

[rmjbn1]

Should have mentioned that P0115

Self clears after so many starts and stops without an error

Maybe 5 or 10 can’t remember now.

Ahhh, maybe that was it, and not disconnecting the battery after all. I can't remember how many times we restarted between the EML coming on and going off as a result of P0115, but not many, certainly fewer than 10, maybe 5 at most.