TD5 electrical question

[ashtrans]

on the defender TD5 the throttle pot has 9 pins labeled ABCDEFGJK, I understand it outputs a 0-5 V signal, so I guess one is earth, one is 5 V and another is the variable signal, not sure what the others are for.

I am trying to identify which 3 these may be and wondered if anyone would know,

many thanks,

[SteveG]

My copy of Rave only shows 7 outputs so must be referring to earlier type throttle sensor. This has two independent input feeds of 5v, two sensor earths that are common at ECU and two sensor outputs which leaves a Red Green wire that I have no idea of.

Sorry can't help with anything useful

here it is from Rave..

The TP sensor is located on the throttle pedal assembly. It detects throttle pedal movement and position. It uses

two position sensors to provide the ECM with the exact throttle pedal position. As the pedal operates, the voltage

of one position sensor increases as the other decreases.

Input / Output

The ECM (C0658-14) provides a 5 volt reference feed to both sensors (C0787-B & C0787-J) on white/purple wires

via header 291. The signal output from sensor 1 (C0787-F) is connected to the ECM (C0658-12) by a white/green

wire. Signal output from sensor 2 (C787-K) is connected to the ECM (C0658-36) by a white/slate wire.

An earthpath is provided for both sensors (C0787-B & C0787-G) on black/yellow wires via the ECM (C0658-26)

The TP sensor can fail or supply an incorrect signal if one or more of the following occurs:

• Sensor open circuit.

• Short circuit to vehicle supply.

• Short circuit to vehicle earth.

• Water ingress.

• Sensor incorrectly fitted.

In the event of a TP sensor signal failure, any of the following symptoms may be observed:

• Engine performance concern.

• Delayed throttle response.

• Failure of emission control.

If the TP sensor fails, the engine will only run at idle speed until the fault is eliminated.

Cheers

Steve

[Guest diesel_jim]

Porny will be the chap to answer this one.

Dave... you making a hand throttle per chance? i fancy doing something like this for my 110 when its built.. i hear that you can buy a plug in box of tricks that has an "up" and "down" button, and it raises the idle accordingly. popular in the states, i wonder if SVO at the factory do such a thing for vehicles using PTO's and hydraulics/engine driven electrical stuff?

[David Sparkes]

I guess if it was easy, we wouldn't have been asked :-)

The answer from SteveG contains nearly all the details. The earlier models used 2 track sensors, wired as described. Later models, from VIN 607225, use 3 track sensors, wired as described, PLUS the Red Green wire which goes back to the Engine ECU.

Later Engine ECUs will accept either 2 or 3 track sensors, but needs a diagnostic system like Testbook to set the parameters. This is shown in the '99 and 2002 models onwards WORKSHOP manual.

I cannot find a stated purpose for the Red Green wire, but with that colouring it must be a switched but unregulated power supply. Green would be (thinks hard) ignition controlled, and fused?

HOWEVER, by a process of elimination, this must surely be the output from track 3

Usefully (grin) there is a diagram in the WM showing the output voltages that would have to be mimicked if someone was to try installing an electrical Hand Throttle. Personally I think your options are either to use a second TPS, switching the output wires between the two, or looking closely at the hand throttle arrangement on a diesel engined Series II and mimicking that. (Basically a sophisticated mechanical connection to the original pedal).

There is no section for the Engine Management System in the 2002 Electrical Library.

Looking at the 2002 on wiring diagram, the connector ports used are B,C,D, F,G, J,K.

Table, based on SteveG's contribution.

B & J are paired, White Purple, 5 volt reference feed.

D & G are paired, Black Yellow Earth.

F is White Green, output, track one.

K is White Slate, output, track two.

C is Red Green, ?? output, track three?? The colour code indicates power in.

Time for a multimeter or scope methinks.

HTH!

[BogMonster]

The purpose of the 3 track pedal is some sort of error correction to detect faults in the pedal output. HOWEVER be aware if trying to replicate the settings for some sort of external control, that the outputs are not linear - among other things we supply speed limiters to fit to Td5 vehicles and the pedal outputs are really odd, there is a "step" in the output near the top and bottom of the pedal travel. If you put 3 multimeters on the pedal outputs and press the pedal down slowly you will see what I mean, or an easier option is to plug it into a Testbook or similar, and watch the pedal voltages on the real time display. Just something to be aware of...

[simonr]

Two track setups are just for noise immunity. A voltage spike will affect both outputs similarly. If increasing the voltage on one line increases the RPM and on the other decreases, the two cancel out - making it fairly immune.

Three track setups are generally a 'majority vote'. If two sensors agree but the third does not, the ecu goes with the majority - and reports a fault.

Spoofing the outputs is perfectly possible - but not easy. The simplest is to set the throttle at the position you want (for fast idle), make up a box with three preset pots which mirror the values of the original - then just switch between the two with either a relay or a bi-lateral switch (on a chip).

Simpler howver might just be a cholkcable which pulls the throttle down against an adjustable stop.

One little project I've been considering for when I buy a Td5 is essentially this, except, additionally, replacing the pedal with an older, cable type and move the throttle pot assembly up in to the dash void (out of the water).

Si

[LandyManLuke]

One little project I've been considering for when I buy a Td5 is essentially this, except, additionally, replacing the pedal with an older, cable type and move the throttle pot assembly up in to the dash void (out of the water).

Si

I've seen a picture of an old type throttle cable, with the TPS inside an IP rated box under the bonnet on the bulkhead. it was a see-through enclosure for added bling too.

[Guest diesel_jim]

I've seen a picture of an old type throttle cable, with the TPS inside an IP rated box under the bonnet on the bulkhead. it was a see-through enclosure for added bling too.

Me too... wasn't that on an ibex? the IP box was up in the middle of the dash wasn't it?

[LandyManLuke]

Hmmm, might have been, it was visible, and as high up as the cable would practically allow, by the looks of things. a while ago now.

[SteveG]

One little project I've been considering for when I buy a Td5 is essentially this, except, additionally, replacing the pedal with an older, cable type and move the throttle pot assembly up in to the dash void (out of the water).

Si

The later units, MY2002 on are sealed and I haven't heard of any water issues with these ones. So if you buy a MY02 onwards, there is no issue, or if an earlier model it would be easier to change out pedal for later 3 track. You might need to change ECU, but if you intend to do things like fuel mapping etc you'll have to change either the ECU or PROM chip anyway.

Cheers

Steve

[David Sparkes]

Three track setups are generally a 'majority vote'. If two sensors agree but the third does not, the ecu goes with the majority - and reports a fault.

Perhaps 'generally', but if we are still talking Defender TD5, then NO.

Reference the TPS output diagram I pointed to in my previous post.

Spoofing the outputs is perfectly possible - but not easy. The simplest is to set the throttle at the position you want (for fast idle), make up a box with three preset pots which mirror the values of the original - then just switch between the two with either a relay or a bi-lateral switch (on a chip).

But this only gives a single preset throttle position, whereas the point about a hand throttle is that it gives the operator a fresh choice of throttle position with each task.

Simpler howver might just be a cholkcable which pulls the throttle down against an adjustable stop.

Simpler, yes, but also cruder, as the cable interfers with normal throttle application.

The point of my reference to a Series based hand throttle system is that it was developed at a time when hand throttles were for everyday use with PTOs. They still allowed the driver to use the pedal if neccassary, when more power was required, but didn't let the engine stall when the pedal was released.

Sorry Simonr,

I intended this as a straightforward response posting, not a posting to 'rubbish' your comments, although someone could get that impression :-)

I am actually wondering if Ashtrans original information request has been satisfied?

Cheers.

[Guest diesel_jim]

Found this link, quite interesting.... you can easily get these things for Jeeps and GM vehicles in the states, i wonder if a call to LR SVO is in order? surely they must do a similar unit for the electricity board Td5's that have winches and hydraulic cherrypickers?

I wonder if matey at the defender centre knows? he's got heaps of ex electricity board rovers there... i was there yesterday, must have been 40 of them, mostly Td5!

[Porny]

or if an earlier model it would be easier to change out pedal for later 3 track. You might need to change ECU, but if you intend to do things like fuel mapping etc you'll have to change either the ECU or PROM chip anyway.

Not as complicated as that... with suitable diagnostic kit, you simply tick 2 or 3 pot.... no need to change ECU's etc etc.

Ian

[David Sparkes]

A 'second thought' makes me wonder if a separate control is neccessary.

I know that most on here only show interest in 38As to sneer at them, but I happen to know that the engines electronic control system is set up to alter the fuelling to cater for additional loads, whether electrical, such as the demand on the alternator of switching the heated screens on, or mechanical, such as the air conditioning compressor being switched on.

There is also engine load compensation, so that the engine can be left at tickover in first gear, and the car will climb a steepish hill, think 1 in 8, providing it starts on the level, and the climb will continue without the accelerator being touched.

Now the TD5 is a later engine, but I recall that there was some early criticism of the engine stalling when faced with slow speed severe climbs. This was answered by a change in ECU programming, increasing the amount of fuel that could be delivered at tickover rpm. On my only visit to the Solihull test track this was demonstrated by a test driver taking the TD5 engined Defender up a steep test hill, with 4 adults in the car. All done at tickover, without touching the throttle. Now the speed across the ground was slow, but it indicates what can be done.

Using these two examples as precedents, if I was in Land Rover, specifying the provision of kit that would put additional load on the engine, and maybe a higher crankshaft speed, then I'd just ensure that when that kit was switched on the Engine ECU was notified of the fact. The speed control would appear to be automatic, as far as driver input was concerned.

As an after-market modifier, if the need is 'just' that the engine needs to keep running, the existing load compensation may be already built in, it seems likely, to me.

A 2000 rpm crankshaft speed (say) may not be quite so accessible, but I reckon Jeremy Fearn or similar could provide a switchable map that would give that high speed. Not sure why you would need it, but that's another question.

I know a hand throttle was a supplementary question in this thread, but just for curiosity, as PTO's are now much rarer, what is the higher idle speed needed for, just hydraulic pumps?

Cheers.

[dougstar]

sorry to go here but where can i copy of the rave manual for my disco 1????????

[LandyManLuke]

Yup, that's off topic!

go to www.green-oval.com