Discovery 2 With 300tdi - Rev Counter and Temperature Gauge

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gordan

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I have a Discovery 2 that started it's life as a V8, but a previous owner retrofitted a 300tdi engine (mechanical throttle control). It runs fine, but the rev counter and temperature gauge don't work, presumably because the signal for those was coming via the ECU.

The question I have is - does anybody know what kind of a signal does the V8 rev counter gauge on the dashboard expect? Is it just an analogue voltage (essentially like a volt meter), does it work as a pulse counter, or something else?

Similarly, the temperature gauge on the dashboard - what kind of a signal does it expect? Does it also operate as an analogue voltage gauge, or a potential divider (i.e. expects a thermistor sensor on the other side of it) or something else?

I am not afraid of splicing into the wiring loom and getting something like an Arduino wired up to generate whatever signals are required to produce meaningful readings on the rev counter and the temperature gauge, but I can find no detailed data sheet spec on what kind of input those two gauges expect.

TIA
 
I believe the tacho used a pulse, it would be interesting to find out if the pulse from the 300tdi alternator would run it, worth a try and you won't cause any damage.

As for the temp sensor, I cannot comment.

Could you please post some pictures of your Disco II with 300tdi engine.

It is an interesting conversion - does everything work as it should apart from some of your gauges? I would be keen to see images from the engine bay etc. In return I'll help you with your electrics once you run some tests to see if it will work.


Thanks.
 
Yes - apart from a couple of gauges and switches, it all runs really lovely (btw, I'm his wife)
 
Welcome back fellow SLUT ;) :hug:

I never really left, I just didn't have anything interesting to say.
Unless people are interested in how I'm usually elbow deep in whatever mess our toddler has made :eek::D

But it's nice to know I've been missed :p
 
I believe the tacho used a pulse, it would be interesting to find out if the pulse from the 300tdi alternator would run it, worth a try and you won't cause any damage.

As for the temp sensor, I cannot comment.

Could you please post some pictures of your Disco II with 300tdi engine.

It is an interesting conversion - does everything work as it should apart from some of your gauges? I would be keen to see images from the engine bay etc. In return I'll help you with your electrics once you run some tests to see if it will work.


Thanks.

I'll be heading out in a minute to take some photos of the damaged bumper we were sent for it, so I'll get some pics of the engine bay for you
 
The BCM is mentioned in the Haynes book, just not where it is, of course, because of the engine transplant, I'm wondering if it's been bypassed as there are a lot wires spliced into the fuse box under the bonnet
 
HI, you better download a RAVE for D2 and start reading if you still have the D2 electronics on it... the rev counter on the D2 is commanded by the engine ECU(ECM)
The tachometer is an integral part of the instrument pack. Located next to the speedometer. it displays engine speed
in revolutions per minute. It is an analogue gauge with a maximum reading of 6000 rev/min.
V8 and diesel variants use the same gauge.
The input for the tachometer is from the ECM. It is a digital signal at 2 pulses per engine revolution. When the ignition
is switched on with the engine not running, the ECM will generates pulses equivalent to 228 rev/min for diagnostic
purposes. The tachometer will not register a reading, as it only indicate engine speeds above 228 rev/min.

so is the temp gauge, also ECM involved:
The engine coolant temperature gauge is an analogue gauge with three sections: cold temperature; normal operating
temperature; high temperature. Under normal engine operating temperatures the engine coolant temperature gauge
will display in the centre of the gauge. When the engine is cold e.g. from first start-up, the coolant temperature gauge
will display in the cold band. When the engine is over heating the temperature gauge will display in the high
temperature band. If the engine coolant temperature gauge receives no input or the input is out of range the
temperature gauge will read cold and the high coolant temperature warning lamp will be illuminated.
The input signal is a PWM signal from the engine coolant temperature sensor via the ECM. The power input for the
high coolant temperature warning lamp is supplied by the instrument pack via fuse 27. The ECM controls the earth
path to illuminate the high coolant temperature warning lamp.

as the original ECM is not there anymore you must be a really skilled elctronist to emulate those signals, let me think about it maybe i have some idea

the other thing which is still there is not BCM but BCU(body controll unit, behind the glovebox, near the slABS ECU), the other warning lamps and gauges are managed through this one
 
Generating a PWM. Signal Modulated by an. Analog Input Using the. TMS320F240 EVM

Discovery 2 diesel conversion

Theres a guy in the breckland club with a td5 body with a 300tdi. Im not sure if its a 300 chassis underneath but its certainly a td5 body. He had to customise the wiring quite a bit I know, as even stuff like the electric windows have an ECU so you have to work out which bits you need to keep, but it can be done and was a very nice and capable truck!

It appears that York Land Rover Services have carried out the conversion.
Unit 1, Forest Business Park, Selby Rd, Fulford, York, North Yorkshire, YO19 4RE
Tel: 01904 625073

Sigler12 on www.discoweb.org has done this conversion.

Muddytrax Discovery2 300tdi conversion
 
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In the D2 the windows and everything else confort related is managed by the BCU, only if it has folding mirrors those have a separate ECU, as the engine was changed everything else can be kept in working order except some small issues

The D2 has a SLABS(self levelling and ABS) ECU which is is untouched, ACE(active cornering enhancement) ECU(if fitted), the rest is managed by that BCU... with the 300tdi engine these are the unsolved problems, the tacho, temp gauge and the engine management warning. also the ABS is bodged somehow cos it needs a throttle position sensor input which on D2 is electronic and it needs the engine speed input too, though the default mode for missing throttle signal/engine speed keeps the ABS function but inhibits the traction controll and normally if the warnings are not disabled they must be on(3 amigos)...and if it has aircon this must be modified aswell cos the compressor clutch and aircon fan were managed by the ECM as well


i'm not sure that analog INPUT converter would work for the temp gauge cos the temp sensor doesnt actually give an input, it's a NTC resistor and the ECM converts it's resistance to signal, as about the tachometer also the ECM works it out based on the crank sensor's inputs... so i'm still thinking but it doesnt seem simple at all...the simplest way seems to convert the instrument pack somehow and addapt proper tachometer and temp gauge to it

not easy
 
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i'm not sure that analog INPUT converter would work for the temp gauge cos the temp sensor doesnt actually give an input, it's a NTC resistor


Isnt it just a Thermistor - in which case 12v on one side and variable voltage out on the other, used as the analogue input to the A to PWM converter?
 
It's a NTC thermistor yes but the gauge works managed by the ECU in 3 positions, cold(down)/normal(middle)/high(up), it doesnt have a linear action, for the D2 management the sensor doesnt work like a simple thermistor cos the ECM makes internal calculations according to the resistance of the sensor on the earth path ... the signal to the gauge from the D2 ECM is well "optimised" in the ECM for those 3 positions it's not a simple analogue - PWM conversion(and it happens at 0-5V not at 12V) ... let's say even if it would work there's nowhere described the waveform/amplitude/baseline of that PWM signal to know how to set a convertor... seems too complicated to me
 
HI, you better download a RAVE for D2 and start reading if you still have the D2 electronics on it... the rev counter on the D2 is commanded by the engine ECU(ECM)

Already got Rave, but electrical rewiring isn't really my thing

so is the temp gauge, also ECM involved:

as the original ECM is not there anymore you must be a really skilled elctronist to emulate those signals, let me think about it maybe i have some idea

the other thing which is still there is not BCM but BCU(body controll unit, behind the glovebox, near the slABS ECU), the other warning lamps and gauges are managed through this one

You are indeed right, I meant BCU

The D2 has a SLABS(self levelling and ABS) ECU which is is untouched, ACE(active cornering enhancement) ECU(if fitted), the rest is managed by that BCU

The suspension has been converted to all coils, so we don't have SL or ACE, and we're pretty sure the ABS isn't working anymore.

with the 300tdi engine these are the unsolved problems, the tacho, temp gauge and the engine management warning.
also the ABS is bodged somehow cos it needs a throttle position sensor input which on D2 is electronic and it needs the engine speed input too, though the default mode for missing throttle signal/engine speed keeps the ABS function but inhibits the traction controll and normally if the warnings are not disabled they must be on(3 amigos)...and if it has aircon this must be modified aswell cos the compressor clutch and aircon fan were managed by the ECM as well

There is a lot of black tape covering up various lights on the dash, so we don't know what warning lights are flashing away under there. The engine that was put in didn't have aircon so that obviously now doesn't work

i'm not sure that analog INPUT converter would work for the temp gauge cos the temp sensor doesnt actually give an input, it's a NTC resistor and the ECM converts it's resistance to signal, as about the tachometer also the ECM works it out based on the crank sensor's inputs... so i'm still thinking but it doesnt seem simple at all...the simplest way seems to convert the instrument pack somehow and addapt proper tachometer and temp gauge to it
not easy

In fairness, the guy that did it put a new temp gauge and a boost gauge in pods on the A pillar, my husband just thinks it's better to have al gauges working on the dash

There are also a couple of other things that don't work, front and rear windscreen heaters, cruise control, the heater is always blowing hot in the drivers footwell, so I'm guessing the BCU has probably been bypassed, hence the birds nest under the bonnet
 
it's a real mess there IMO, the BCU can't be bypassed cos you'll not have central locking/alarm/indicators/hazards/fog lights....and many more, if you have RAVE read the description of BCU and IDM(part of the interior fusebox)... the cruise controll can't work without the original ECM, nor the aircon but the screen heaters and the heater assy must have some particular problems... as i said to bring it as close as the original would be a DIY job only for a skilled electronist who knows how a D2 works
 
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