Fan on, stop light on constantly

[bertone19]

Heya been searching through forum have found similar issues but none that quite hit nail on head. Just had newborn so worst time to have car doing this but hey..

Its a 1.4 petrol 2003, 97,000 miles, lx model i think

Fan is on all time from start up, temperature gauge shoots to red from start up too and the engine stop light flashes constantly too..

Changed thermostat, coolant sensor, voltage checked fuses, relays and wiring seem ok.

Reset ecu via diagnostics machine - which only showed the 1 code that being the coolant sensor, and reset the code. Gauge and stop light go for 3 seconds then return to red. Reader does say engine coolant is minus 40!

Reset ecu by shorting battery, and left battery off overnight, no change either time.

From the forum, can see similar issues pointed to corroded relays and wiring, possible earth fault, fan switch(?) or ecu not behaving.. ABsoulutely any ideas on this would be greatly appreciated

[Capncol]

Hi and welcome to the forum

(I deleted your duplicate post BTW)

Firstly never ever short the battery. It's dangerous. Always use the BSI reset as shown on this forum.

My first thought is - Are you sure it was the temp sensor you changed?
Did you get that error after the sensor change?

Either way, it sounds coolant sensor related to me.

[bertone19]

Hi and thanks for deleting duplicate(!)

Can say i'll never short the battery again, more i wont let the mechanic short it again. Have forwarded the BSI reset procedure to him and he is going to try it this afernoon.

99.9% certain was temp sensor. Looking onto engine from front its to right of engine at top, above the thermostat housing and has the green plug going into it. Bought from local parts supplier who went through the blueprints of this 1.4 engine to get right part..

And yes the error came up again after fitting, and this is the second new one its had as was at another garage before and they changed it too. We just tried another new one just in case as it all points to sensor problem of some kind. As well as resetting bsi like you say, maybe the wiring to sensor is causing problem? Nothing obvious from outside but didnt know if the plug inside was worn at all..

[Capncol]

What happens if you disconnect plug? Does it still read hot?

[bertone19]

Yes

[bertone19]

Which kind of says the wiring/plug isnt at fault?! Have seen suggestions about voltage regulators on the dashboard circuit giving faulty reading to the temp gauge, not certain this would make the fan stay on all time? Also seen there should be couple of relays on bottom of radiator that could have corroded and broke over time, from memory didn't see any relays but apparently they are under a cover so will look again when i go back to garage. Going there in an hour or so, dont know yet if mechanic has tried the bsi reset yet heres hoping

[bertone19]

Just phoned mechanic he's done bsi reset no difference. Hasn't got to try spare ecu yet just in case.

Says theres only one relay bottom of rad but hasnt checked it, says it wouldn't cause these issues anyway.

[Capncol]

Whoa! Hold on!!
You can't just swap the ECU as it's intergrated with the BSI / Immobiliser.
The temp sensor talks to the ECU and the ECU tells the dashboard what temp to display and tells the fan(s) when to come on and off. If disconnecting the plug from the sensor gives the same result, then check the wiring from the plug to the ECU. The ECU is obviously getting false signals for it to tell fan to come on, display temp as hot and put the *STOP* alert up on the dash (unless the ECU itself is at fault)
Tell me what system it is and I should be able to give you the pinouts.

[bertone19]

Ok considered us i 'whoa' mode. Like i say he hasn't picked a spare on up so no danger now. Phew..

I wont see car until tomorrow now will find out what the system is and get right back to you.

Pretty sure checked wiring from plug to ecu already but will confirm/do again.

Have since found out about another sensor which can affect the fan etc, the blue engine management sensor on the cylinder head apparently. Have one reserved for pick up in morning to try, same page said about a brown sensor 'hiding underneath'. Doesn't elaborate where underneath, and the parts co could only think it meant the fan switch?!

Really appreciate your effort here Capncol

[Capncol]

Have since found out about another sensor which can affect the fan etc, the blue engine management sensor on the cylinder head apparently. Have one reserved for pick up in morning to try, same page said about a brown sensor 'hiding underneath'.

What blue sensor? Where have you got this info from? Got a photo?

[bertone19]

Found both on google search when found this forum, and from parts manager who got up the drawings etc for engine from Peugeot he said. Engine Management Sensor its called and situated on cylinder head apparently. Dont have a photo as not near car and havent seen it myself yet, will look in morning though when go to garage. Links below where they post about these sensors if that helps

http://www.bba-reman.com/forums/Topic46 ... ageIndex=3

[Capncol]

OK, but that link is for a "W" reg 1.4 which is pre plex. Yours (at '03) is later plex model, so different set up.
Engine management sensor sounds like a generic name for all the sensors. They do have different functions (to do with engine management) but are named by what they do e.g. ECT sensor = engine coolant temp
CKP= crank position indicator TPS= Throttle position sensor etc:
As I said before- Let me know the engine management system (will be on the ECU or your mechs scan tool should tell you)
and I will give you the pin outs and resistances.

[bertone19]

okies will do tomorrow bud