Thread: Which sensor now!

Cant go and test mine now, but from memory if it thinks the sensor has failed it checks it against the fuel cooler temperature and gets a calculated value for teh gauge.

thanks, your right by what the workshop manual says, but need to know what happens in reality, mine drops to a 1/4 on temp gauge and raises revs as if the motor on choke cycle indicating the default feul temp is not working.....

The inputs and outputs for the FT sensor are 5 volt supply and signal out. In the event of component failure the ECM

reverts to a fixed value of 60 °C stored in its memory.

looking forward to your reply

Ok, Ive just been out and tested it on mine (Defender not D2)

The car is warm, but not hot, and I havent got the time to pop out to get it hot now.

When I removed the plug the gauge dropped right down, although it still seemed to run happy enough.

the WSM lists a number of possible symptoms if the sensor fails inclding driveability concerns

thanks mate, much appreiciated,

your idle didnt increase?!,

reason i ask is when started from cold my truck is relatively smooth through the rev range, but when up to op temp, feels off key beween 2500 to 3000rpm, like the timing is out on an old petrol donk , then retuns to normal percieved opp at 3000+rpm with cammed kick in the pants,

replaced MAF and that got rid of hesitation hicups under hard acceleration, but this retard zone still prevails

Hi,

Correct, I got no increase in idle atall, but as I said it wasnt hot, only warm (water temp of about 60 degrees)

Rgds
Pete

If the D2 TD5 coolant sensor is disconnected, the temp gauge needle should drop to the bottom and the high temp warning light should be on. That's the LR specified and observed (by me) indicator of the coolant sensor with out-of-range resistance. If the needle is only going down to 1/4 then I'd start by looking for oil in the ecu harness at the ecu affecting the resistance of the coolant temp circuit.

Originally Posted by SO69WA

thanks mate, much appreiciated,

your idle didnt increase?!,

reason i ask is when started from cold my truck is relatively smooth through the rev range, but when up to op temp, feels off key beween 2500 to 3000rpm, like the timing is out on an old petrol donk , then retuns to normal percieved opp at 3000+rpm with cammed kick in the pants,

replaced MAF and that got rid of hesitation hicups under hard acceleration, but this retard zone still prevails

Try cleaning the AAP sensor (on the side of the airbox) be careful with this sensor they are very expensive, contact cleaner is best, also clean the EGR as this can get clogged with oil and soot.

Oil in the injector harness will cause rough running, check this as well.

Check the wastegate modulator for cracks in the hoses and also check the modulator itself.


Baz.

thanks for the feed back,

my concern is the fuel temp sensor opp properly, as its the sensor the ecu reverts to if the coolant sensor fails and then in theory the ecu reverts to a set value of 60'c, in the event the fuel sensor fails, hence my thinking that on light throttle when warm theres a mismatch in fine tune fuelling, i would disconnect/change the sensor to confirm but its a absolute pain to tinker with gven its location so will have to pony up for mechanic intervention, if we conclude its suss

In the event of component failure the ECM calculates coolant temperature from the fuel temperature sensor signal. If

this occurs, the limit engine operation if coolant temperature is too high becomes inoperative.

Fuel Temperature (FT) sensor

The FT sensor is located at the rear of the engine in the fuel rail with the tip of the sensor inserted at least 10 mm into
the fuel flow. This allows the sensor to respond correctly to changes in fuel density in relation to fuel temperature.
The FT sensor works as a NTC sensor. As fuel temperature rises the resistance in the sensor decreases. As
temperature decreases the resistance in the sensor increases. The ECM is able to compare the voltage signal to
stored values and compensates fuel delivery as necessary for hot engine start.
The operating range of the sensor is -40 to 130

°C (-40 to 266 °F).

Input/Output

The inputs and outputs for the FT sensor are 5 volt supply and signal out. In the event of component failure the ECM

reverts to a fixed value of 60 °C stored in its memory.


FYI have cleaned AAP, MAP, disconnected EGR for diagnostic, no change, replaced MAF,

how much is a new Harness, do you have to see oil at the plug end to be suss or can the problem exist before that,