Engine fault code

laughingboy

i bought a bluetooth OBDII scanner recently and tried it on my car (using the torque app), however it says there is a stored fault:

P0118 Engine Coolant Temp Circuit Input High
http://www.obd-codes.com/p0118

the engine warning light is not illuminated on the dash.

i also checked the reading of the coolant temperature using the app, it said -40!

car is a pug 106 petrol indy 2001

its been to a garage, they replaced "green and blue" sensors which hasn't changed anything

as i understand it the "green sensor" (which has 2 wires) is the ECU monitor of the temp

the "blue sensor" (1 wire) is the dash light temp warning sender

is my understanding correct here?

anyway i unplugged the green sensor and shorted the contacts. the temp reading was still -40. i then shorted the 5V contact to another earth point and the temp went up to 143 (seems reasonable)

then with blue sensor, i shorted the only contact to ground (expecting dash light to come on) but the dash light did not come on and the temp reading went up to 143 again??! i thought this sensor had nothing to do with the ECU

any ideas on what might be going on here?

i did think the green sensor had a bad earth conn for some reason, but following playing with blue sensor, i think i have confused myself!

thanks

Geodark

laughingboy wrote: »

i bought a bluetooth OBDII scanner recently and tried it on my car (using the torque app), however it says there is a stored fault:

P0118 Engine Coolant Temp Circuit Input High
http://www.obd-codes.com/p0118

the engine warning light is not illuminated on the dash.

i also checked the reading of the coolant temperature using the app, it said -40!

car is a pug 106 petrol indy 2001

its been to a garage, they replaced "green and blue" sensors which hasn't changed anything

as i understand it the "green sensor" (which has 2 wires) is the ECU monitor of the temp

the "blue sensor" (1 wire) is the dash light temp warning sender

is my understanding correct here?

anyway i unplugged the green sensor and shorted the contacts. the temp reading was still -40. i then shorted the 5V contact to another earth point and the temp went up to 143 (seems reasonable)

then with blue sensor, i shorted the only contact to ground (expecting dash light to come on) but the dash light did not come on and the temp reading went up to 143 again??! i thought this sensor had nothing to do with the ECU

any ideas on what might be going on here?

i did think the green sensor had a bad earth conn for some reason, but following playing with blue sensor, i think i have confused myself!

thanks

A stored fault could be an old fault that hasnt been cleared - have your tried clearing any faults and then seeing if the fault happens again?

laughingboy

Geodark wrote: »

A stored fault could be an old fault that hasnt been cleared - have your tried clearing any faults and then seeing if the fault happens again?

oh yes forgot to mention, i did clear the code using the app and also disconnected the battery for a couple of days. fault code came back again on both occasions, and temp reading still said -40.

thanks, always good to check the obvious!

forgotmyname

What does the temperature read after a good run? What does the gauge show?

Some sensors dont start to read until about 40 degrees which maybe the issue.

Mine says 40 degrees even stone cold. It cannot drop below that. I think the sensors have a smaller working range to make them more accurate in that range.

Is it actually picking up the right sensor?

laughingboy

thanks, the temperature of -40 (minus!) is read from the torque app using the OBDII scanner

the car doesn't have a temp gauge on the dash, it only has a warning light for if it gets too hot.

went on a 2 hr drive and the sensor was reporting -40 for the entire duration

whether its picking up the right sensor im now very confused about. i thought the "green" was for the ECU monitoring and "blue" the sender for the dash, so on completely different circuits. but shorting both results in ECU temp going to max

laughingboy

any other thoughts?

i would like to check the continuity of the ground wire from the sensor to the ECU but i'm not sure which pin the wire goes to on the ECU. is there any resource available that would show this?

also, when I simulated a hot condition the cooling fan did not come on (the ignition was on, but the engine was off)

thanks

spacey2012

One of these readers in the wrong hands will quickly empty your bank account.
The assumption that the fault must be the sensor showing the code has skint many a amateur mechanic.
If the car is running with no EML lights on, put the code reader down and step away from it.

The 106 has no variant temperature sender unit, only a I am over heating sensor, it will be just a spare wire on the loom, hence why the EML is off.
You can not replace what is not fitted.

The Circuit will be high, it is not fitted to this car.

laughingboy

thanks, but I don't think a bit of probing around will empty my bank account!

as far as I know (and i beleive i am correct on this) there are 2 coolant temp sensors.

one goes to ECU for reading coolant temp (this is 2-wire). the second goes direct to the dashboard for illuminating the over-temp light, this is a single wire (the i am over temp sensor!)

spacey2012 wrote: »

One of these readers in the wrong hands will quickly empty your bank account.
The assumption that the fault must be the sensor showing the code has skint many a amateur mechanic.
If the car is running with no EML lights on, put the code reader down and step away from it.

The 106 has no variant temperature sender unit, only a I am over heating sensor, it will be just a spare wire on the loom, hence why the EML is off.
You can not replace what is not fitted.

The Circuit will be high, it is not fitted to this car.

spacey2012

If it bothers you trace the unused variant temperature sender wire and fit a 15k resistor to it, the "code reader" will ignore it then.

tedted

of course it has a ect,wire no 1235 goes from the sensor to the ecu,pin no 25.pin no 26 on the ecu is the feed for it but it also feeds the tp sensor and the iat sensor,this wire no is 1336 to the sensor

spacey2012

Have you tried the Pug software or are you using a generic OBDii software.
I find it strange your free/ e-bay software is reporting a DTC and the cars own DTC is not.
Why would you trust your software and begin tracing a non fault, is it some kind of college project ?
You can not retrofit the required sensor as well as that engine has no place for it to be fitted.
It is omitted on that car.