Technical brava coolant circuit error - P0115

[teaboy100]

Hi all

Just joined hoping you can help with a problem on a friends Fiat Brava. Its an 80 sx 1.2 manual, no aircon, model year 2001.

She took it to a local garage a couple of weeks ago, as it wouldn't start very well, and it ran badly. Also the temperature gauge was flicking up and down.

Garage found error codes P0115 and P0340, and had to refill the radiator .

They replaced the cam sensor, and the temperature sensor (brass fitting near thermostatic valve). However, on road testing, the error codes are still present. They gave the car back to her, saying it needed to go to Fiat to be properly diagnosed on a fiat machine...

So, my OBD scanner confirms the 2 error codes. It also shows a coolant temperature of minus 40 degrees. If I take the plug off the sensor and short 2 of the wires, the coolant temp shows positive 266 degrees. I'd say the sensor was duff, but its just been replaced.

The engine starts and runs ok. It warms up fine, and the radiator hoses are all hot to the touch. The internal heater delivers hot air.
The dashboard gauge needle goes to the half way position, which seems ok, but then begins to flicker up and down slightly, which isn't ok.

The radiator fan is on all the time even when the engine is cold. This is wrong but I can't find a separate switch or sensor for this. Is it controlled by the ecu?
Removing the fuse allows the engine to warm up correctly.

I had to clean up fouled plugs and throttle body, but I guess the engine is running rich due to the ECU using its default settings instead of receiving an accurate water temp reading.

My apologies for a rambling post. Hopefully there's enough here for you to diagnose something.

Many thanks for your time and expertise.

 

[The Professor]

Based on those error codes, I'd have made the changes the garage did. However, it sounds like the coolant temperature sensor still isn't working. Bit of an obvious one, but the sensor is new? The fluctuating temperature gauge could be a red herring. There is a known fault with the gauge caused by a poor electrical connection behind the dashboard. My gauge variously reads correctly, low or a bit high depending on its mood and a sharp thump on the top of the dashboard restores sanity.... until the next time.

 

[teaboy100]

Thanks for that Professor. Yes I took the sensor out to look at it, and its quite shiny with no coolant stains on it, so I guess its new. I'll have a go at replacing the 'new' thermo sensor. Having done a quick internet search, I can't locate anyone selling this part. Does anyone know of a good fiat parts supplier that I can order from.
I noticed that the crankcase breather pipe has been torn and taped up, so I'll need to source one of those too.

regards

 

[The Professor]

How about here for the sensor: https://www.shop4parts.co.uk/index.cfm?action=catalogue.list

 

[teaboy100]

Ok, been away for a while, but now back to try and fix this problem.

I've bought a new temperature sensor and fitted it, but this hasn't cured the P0115 error code, and my scanner still shows a water temp of minus 40 degrees, so I'm baffled. Any further suggestions gratefully received!

On the fan issue, it still comes on when the ignition key is turned despite the engine not running off, and/or cold.
Is this connected to the Coolant Circuit (P0115) error above?
Obviously removing the fan fuse stops it.
I also removed the fan relay (in the box in front of the battery). This produced an error code of P0480, so I'm assuming the relay is OK.

I only have an OBD scanner. Is there another level of Fiat specific diagnostics that I can't access, does anyone know?

 

[teaboy100]

Just an update. The car still shows a P0115 error code. I swapped the fan relay for another relay, but the fan still comes on with the ignition.

Is it possible that the ecu is faulty? If so, can they be fixed, or is it replacement time?

cheers
Jon

 

[JoskeJTD]

Just an update. The car still shows a P0115 error code. I swapped the fan relay for another relay, but the fan still comes on with the ignition.

Is it possible that the ecu is faulty? If so, can they be fixed, or is it replacement time?

cheers
Jon

I dont think the ECU controls the fans on the 1.2. I know the HGTs ECU does.

Does the car run fine now except for the fans being on all the time?

 

[teaboy100]

Hi, thanks for your post.

No, the car doesn't run correctly. Scanner still shows a P0115, and the coolant temperature is still showing as minus 40c, which results in the engine running very rich.

I was hoping to find a blown fuse, but I've checked all of them, including the ones hidden behind the fuel pump relay on the bulk head, and the 7.5 amp fuses that allegedly protect the coolant circuit, under the dashboard.

The radiator fan is on all the time. I can turn it off by removing the 30a fan fuse, or the 7.5a fuse under the steering wheel, or the 15a fuse behind the fuel pump relay, or removing the fan motor plug.

I've also checked the fan relay, by swapping it with the headlight relay (and with the ecu relay thats next to the fuel pump relay).

Last night I disconnected the battery to see if the ecu would clear by today, but no change when I reconnected this morning.

If I remove the fan relay, I get an additional P0480 error code. In all other tests, there is only the P0115.

Do you know what the sensor is thats on the top of the engine. Might it be a cam sensor. The wiring from this sensor joins the wiring from the coolant temp sensor on its journey to the ecu.

The haynes manual I'm using only goes up to 1999, but this 1.2 model is 2001, so the wiring diagrams are not correct.

Baffled.

 

[synchro]

Do you mean the sensor on top of the camshaft cover? This is a knock sensor.

 

[teaboy100]

Hi, yes on top of the engine cover. It has a 3 pin connector. If I remove it, I can see into the engine partly, and there is oil on the base of the sensor.

I only ask, as I've obtained a wiring diagram that shows a coolant sensor with 3 wires, and was wondering if this sensor was part of the problem on this car. I'll leave it alone if its the knock sensor, thanks.

 

[T14086]

map ensor is 3 wire at back of engine (top) normally to have oil on it, I would check for air intake leaks first.

 

[teaboy100]

Hi, how would air leaks cause a P0115 coolant circuit sensor error? Or cause the radiator fan to be on all the time?

Thanks re the info about the map sensor. I looked in the haynes manual, and it shows the knock sensor to be on the underside of the engine.

thanks for your help.

 

[T14086]

it wont, I never read the post properly

 

[JoskeJTD]

If anything i would still say its either the wiring to the thermostat, the connector to the sensor on the thermostat or the thermostat sensor or map sensor (typically causes 1.2s problems).

Even new parts fail and if you buy the wrong sensor it wont work correctly either. To be honest i've never known them to come seperate. Everytime I replace a thermostat, i replace the whole thing.

I'll just check yours on eper...

46523118 Complete Thermostat (No seperate Sensor) - Approx £12

I cannot find any type of temp sensor on eper, so i can only think that the fans are controlled by the ECU. I can only suggest you try and change the thermostat. Your reading of -40 degrees would not trigger the fans to come on in the real world as the radiator wouldn't need cooling. More like heating. However since the OBD socket on the car isn't a true OBD socket working the same protocols as todays car i can only assume your reader can't read live data correctly.

 

[teaboy100]

Hi JoskeJTD

I'll have a go at replacing the thermostat, its probably due to be changed anyway. There are definitely no wires leading from it, so it must be mechanical only.

Its possible that my scanner doesn't read the codes correctly, but it does give me the same error codes that the garage found, and I can pull various other sensor plugs and provoke relevant P codes (and also reset them, luckily!). The only code that stays in memory is the P0115.

I don't think I have an issue with the MAP sensor. Most of the time, my experimenting is with the engine off, but ignition on. Running the engine usually gives an additional P0340. General advice indicates that fixing the coolant circuit is the first thing to do.

I got hold of a multimeter, and checked the temp sensor plug. With the ignition on, I got a 5 volt reading which I think is correct. Does this mean the wiring is OK all the way back to the ECU? The temp gauge in the car works when the engine is warm, so that indicates the other 2 contacts in the plug plus the wiring and the thermistor, are working (I hope).

Thanks for your help and time.

 

[JoskeJTD]

Hi JoskeJTD

I'll have a go at replacing the thermostat, its probably due to be changed anyway. There are definitely no wires leading from it, so it must be mechanical only.

Its possible that my scanner doesn't read the codes correctly, but it does give me the same error codes that the garage found, and I can pull various other sensor plugs and provoke relevant P codes (and also reset them, luckily!). The only code that stays in memory is the P0115.

I don't think I have an issue with the MAP sensor. Most of the time, my experimenting is with the engine off, but ignition on. Running the engine usually gives an additional P0340. General advice indicates that fixing the coolant circuit is the first thing to do.

I got hold of a multimeter, and checked the temp sensor plug. With the ignition on, I got a 5 volt reading which I think is correct. Does this mean the wiring is OK all the way back to the ECU? The temp gauge in the car works when the engine is warm, so that indicates the other 2 contacts in the plug plus the wiring and the thermistor, are working (I hope).

Thanks for your help and time.

Thats the problem, i can't locate the temperature sensor plug on eper. There is no mention. If the thermostat is mechanical, which i believe it is then it wont clear the error code as that is an electronical issue. Where is the temp sensor on your car?

 

[teaboy100]

Hi again

The sensor is just above the thermostat, but is separate from the thermostat housing. It has a black square 'female' plug with 4 pins inside. The top 2 pins feed the dash gauge, and the bottom 2 feed the ECU. I believe its called a double sender unit or something like.

I bought this unit online from Simpson Supplies. COOLANT TEMPERATURE SENSOR SI1128R ALFA/FIAT.
It fits a whole bunch of cars, but it is the same as the one that's in the engine already.

I agree, replacing the thermostat won't affect the error code.

 

[teaboy100]

OK, good news. The car's finally fixed. And before anyone else posts what a sad sorry excuse for a diagnostic technician I am, I've beaten you too it!

My first outing with a multimeter was my downfall. I thought I was doing something wrong trying to measure the resistance in both the fitted sensor, and the new sensor plug that I'd bought. Turns out both plugs are not correct for this model year car, and I was attempting to get a measurement between two pins that weren't connected to the same thermistor.

Anyway, I'm boring you know. The fix was simple - I swapped the wires over in the sensor plug and refitted it. Result - radiator fan is off, temperature shows as 36 degrees (engine cold), no fault codes present.

The car starts fine, runs fine, gets hot OK, temp goes up to 165 degrees on a run, and still no error codes. I'm so happy...
And I checked that the rad fan kicks in when the rad gets up to 200 degrees. Ace.

One minor glitch is the the dashboard temp gauge doesn't move, so I guess the rewired plug isn't right. But I don't care...I can fix that another day.

Thanks for the support. I appreciate you guys taking time to come up with your ideas etc.
My advice to others reading this, is never assume anything, even if you've think you've bought the correct new part!

Happy motoring people.

 

[donntonny]

OK, good news. The car's finally fixed. And before anyone else posts what a sad sorry excuse for a diagnostic technician I am, I've beaten you too it!

My first outing with a multimeter was my downfall. I thought I was doing something wrong trying to measure the resistance in both the fitted sensor, and the new sensor plug that I'd bought. Turns out both plugs are not correct for this model year car, and I was attempting to get a measurement between two pins that weren't connected to the same thermistor.

Anyway, I'm boring you know. The fix was simple - I swapped the wires over in the sensor plug and refitted it. Result - radiator fan is off, temperature shows as 36 degrees (engine cold), no fault codes present.

The car starts fine, runs fine, gets hot OK, temp goes up to 165 degrees on a run, and still no error codes. I'm so happy...
And I checked that the rad fan kicks in when the rad gets up to 200 degrees. Ace.

One minor glitch is the the dashboard temp gauge doesn't move, so I guess the rewired plug isn't right. But I don't care...I can fix that another day.

Thanks for the support. I appreciate you guys taking time to come up with your ideas etc.
My advice to others reading this, is never assume anything, even if you've think you've bought the correct new part!

Happy motoring people.

Hello i have the same problem can you tell me what exsactly you did to your car

 

[varesecrazy]

Hello i have the same problem can you tell me what exsactly you did to your car

that was SIX years ago, maybe use the e-mail option..,

Charlie