2001 Disco 2 TD5 Driver demand fault

I tried searching but I think the search function is still down.

After a bit of help please. I have the EML + S + M lights on and my Foxwell nt510 is coming up with a driver demand fault. I can look at the 3 tracks and see the voltages changing up and down but don't know what they should be. Any pointers where to start please?

Cheers

Read the fault code stored in the autobox ECU too se we'll see if it matches the EMS one ... the accelerator tracks should be: T1 + T2 = supply , T3 is irrelevant,

at idle T1 = around 0.6V (+/- 2) , T2 = supply - T1

At idle T1 = 0.062, T2 = 4.41, supply = 0,
At full throttle T1 = 3.51, T2 = 1.61, supply = 10
Supply goes up steadily from 0v to 10v.

AT ECU

The descriptions :
1. (21) = The CAN message from the engine management controller which informs the transmission of the engine torque is invalid.
2. (12) = The CAN message WFPDK indicates to the transmission controller the driver demand (ie accelerator pedal position). , which is sustaining the ECM's driver demand fault code

can be faulty TPS or even worst engine ECU or wiring issue... if you are handy with electrics and you have RAVE i'll tell you where to measure if the ECM is actually delivering the 5V supply but the concerning thing is that reverse 10V supply input which comes from the ECU

BTW the Foxwell didnt give you the code's P code too?

Thanks sierrafery.
I checked pin 14 on the ecu connector and it was around 2v. I disconnected the tps connector from the brake pedal and reconnected it and now T1 and T2 have similar voltages starting low and going up. I've also checked the ecu for oil and it is spotless.

Just going to check the xyz switch cos my local independant keeps telling me it's probably faulty as the M & S lights do come on very occasionally.

backinblack said:

I checked pin 14 on the ecu connector and it was around 2v. I disconnected the tps connector from the brake pedal and reconnected it and now T1 and T2 have similar voltages starting low and going up

Click to expand...

IMO dont mess with the XYZ switch, the M+S lights are coming on due to the CAN fault code, if it was the switch it would have triggered other code..... if you get only 2V on pin 14 of the black plug you need another ECU

My current thinking is the xyz switch may be faulty causing the ecu to switch off the tps. I don't realy think the xyz is faulty as the foxwell shows if the car is in park or 1st gear.

BTW no P Code. It might if I use the ODDBII function instead of the LR specific function

It's no such thing in the management like the EAT ECU to make the ECM to switch off TPS nor that a XWZ fault to bring on the MIL too without logging a specific fault code, the problem is with that 2V supply and the erratic readings which are all managd by the ECM... the CAN messages have allocated a P code as well but it should have been together with the description in the LR protocol, the OBDII protocol is not compliant with the D2

Is pin 14 on the ecu the correct one, the rave manual says input 5v not output but I can't find an output to the tps.

Measure the voltage at pin 14 black plug(that's the supply) with TPS unplugged cos it might have an internal short and create a voltage drop on the supply, if then you get 5V replace the TPS and if still 2V replace the ECM , the XYZ switch has nothing to do with that believe me

btw, the TPS is not on the brake pedal

backinblack said:

I disconnected the tps connector from the brake pedal

Click to expand...

Good shout on the voltage with the TPS unplugged, I'll check that tomorrow. I will also put the xyz switch back on

Been a long day

If you check the TPS description in RAVE - Engine management description you'll see that they name the output from ECM to sensor like " Input to the throttle pedal position sensor is via pin 14 of the ECM connector C0658" ... that can create a confusion , Good luck, let's hope it's not a short in the wiring

Cheers.

Update. I have had the engine running all morning (much to the neighbours delight ) and now the battery has gone above 13.9v I have 5v supply on pin 14. The foxwell still reports 0v on driver demand supply and I still have my EML and M&S lights. They clear if I clear the AT fault log but then come back again. Got to go out soon so it will have to wait a while now.

IMO you have to replace the TPS

IMO you are right. I think I may need to get it on a proper testbook, not too happy that the foxwell is reporting 0v on supply when it's got 5v. I also have 4 or 5 5v readings on the TPS end when disconnected which I suspect is correct.

So do you get 0V reading with Foxwell with TPS connected while you can read 5V with multimeter then? ... it's strange but maybe the ECU is monitoring the return voltage on the earth path to show the real supply of the TPS and that's what it reports, i dont know that exactly cos i didnt investigate this myself yet(i hope i'll not have to , Foxwell is a quite accurate tool though

Yes the foxwell reports 0v while the multimeter reads 5v on ecu. Was thinking that it may be measuring the return voltage myself, not much point the ecu using a supply as a reference voltage as it could not detect a fault. Can't see it measuring 5v on an earth either cos earth would have to be 0v.

Can't find any ref to tp sensor 3 pin on ecu so maybe there's a different diagram for that one.

I didnt say earth but earth path which is managed also by the ECU and on other systems it sends a PWM control signal on it as to check the involved part's integrity... if i was you i'd replace the TPS and see what happens or find somebody near you with hawkeye or nanocom to double check cos at this point the ECU is suspect too as it might not send accurate info on the diagnostic line... quite complicated so you have to rule out things one way or another