Rav4.2 Milage Computer Information

[St Thicket]

I came over a connector pinout description yesterday showing the fuel and speed input, and have been thinking about using these signals to create my very own milage display... since I have replaced my original rubbish stereo with a new single din player, I obviously lost this information.

What I have to know before making doing this, is what kind of signals that are provided on the different pins:

pin 5 and 6: Fuel signal

I bet that this is a pulse signal, but I'm not sure. The question is what it tells? Is it pulses pr liter, or the pulse width telling how long the nozzles are activated? If this is the nozzle activation, then i need to know the flow through the nozzles when activated. (rail pressure and nozzle dimension for the 2.0 D4D could be sufficient i think)

pin 16: Speed Pulse Input

As I far as I know, this is pulses from the gearbox, or perhaps directly from the wheel. The question is, how many pulses pr wheel rotation? I think it might be 4, but I'm not sure.

Pin 12 and 13: Oustide (ambient) temperature

This is most likely the pins directly to a thermistor (ntc resistor). I saw something similar in a corolla workshop. The question is if the wheatsone bridge is included in the sensor, or if this must be created on the reciever...

All help would be highly appreciated. If I make this work, then I'll share it with you all. I bet there's a lot of you who have replaced the original stereo...

EDIT: The heading wasn't the best ever... is it called "driving computer" or "fuel efficiency computer" or what?

[Hoovie]

I think a popular option in this situation is to buy a Scangauge II and install one of those, but your project sounds more fun if you want to build your room specifically

[St Thicket]

Well, As far as i know, the D4D engine does not support OBD2. The scangaugeII is also quite big, so then I'll have problems finding a good spot to place it.

Since I'm a big electronics geek, I'd like to build one myself just because I can :-)

But if someone know how to read information through the service bus of my diesel, please let me know! I bought the ELM327, but it doesn't work...

[anchorman]

It supports OBDII from the face lifted 4.2 - i.e. with the round spot lights.

[St Thicket]

yeah, i know... unfortunately, I have the 2003.

Does my car have obd then? Or is it a special bus that only toyota knows?

[anchorman]

yeah, i know... unfortunately, I have the 2003.

Does my car have obd then? Or is it a special bus that only toyota knows?

Can you get your hands on a cheap reader and see if it recognises the protocol?

[shcm]

pin 5 and 6: Fuel signal

I bet that this is a pulse signal, but I'm not sure. The question is what it tells? Is it pulses pr liter, or the pulse width telling how long the nozzles are activated? If this is the nozzle activation, then i need to know the flow through the nozzles when activated. (rail pressure and nozzle dimension for the 2.0 D4D could be sufficient i think)

Having a very quick look at the 4.2 documentation, assuming it's the diesel and basing it on face lifted wiring diagrams (it's all I have, but it probably didn't changed much) it's a separate output from the the EMS ECU.

For the petrols, it appears to be tapped directly off the injector drive signals. Sorry can't tell you if it the diesel is PWM or just a pulse per unit fuel used. How about a bit of reverse engineering with a 'scope?

If it is not PWM, maybe you'll need a bit of hardware first to count all the pulses over one tank full of fuel? With that, the fuel added on the next fill and the distance covered, you can workout a reasonable figurefuel per pulse? Sorry, can't find the actual pulse specification. Maybe somebody else will be along soon who does have it.

pin 16: Speed Pulse Input

As I far as I know, this is pulses from the gearbox, or perhaps directly from the wheel. The question is, how many pulses pr wheel rotation? I think it might be 4, but I'm not sure.

It's most likely a "conditioned" speed signal output by the instrument pack. Again, a portable scope or scope+inverter plus an assistant and speedo will probably give you all the info you need?

Pin 12 and 13: Oustide (ambient) temperature

This is most likely the pins directly to a thermistor (ntc resistor). I saw something similar in a corolla workshop. The question is if the wheatsone bridge is included in the sensor, or if this must be created on the reciever...

Can't find any info at all on that either! (not being much help am I?) I would expect the sensor just a simple thermistor type only - resistance between two terminals, no "active" components or bridge.

Cheers

[St Thicket]

Thank you for your reply! If you have the documentation, then you'll probably find what i need.

I'll see if I can get hold of a portable osciloscope, or perhaps a DAQ, so that I can verify the data. But it is allways nice to know what I should look for before I start measuring.

Having a very quick look at the 4.2 documentation, assuming it's the diesel and basing it on face lifted wiring diagrams (it's all I have, but it probably didn't changed much) it's a separate output from the the EMS ECU.

For the petrols, it appears to be tapped directly off the injector drive signals. Sorry can't tell you if it the diesel is PWM or just a pulse per unit fuel used. How about a bit of reverse engineering with a 'scope?

If it is not PWM, maybe you'll need a bit of hardware first to count all the pulses over one tank full of fuel? With that, the fuel added on the next fill and the distance covered, you can workout a reasonable figurefuel per pulse? Sorry, can't find the actual pulse specification. Maybe somebody else will be along soon who does have it.

I bet that it is PWM too... documentation should tell something about this in the "service spesification" section. I found something like this in a 2004 corolla service documentation, and it spesified the fuel injection volume. It might be some similar data in the rav4 documentation.

Here is the corolla pdf page

It's most likely a "conditioned" speed signal output by the instrument pack. Again, a portable scope or scope+inverter plus an assistant and speedo will probably give you all the info you need?

I'll probably find this very easily. Just keeping a fixed speed, and reading the frequensy, and then divide with a parameter... shouldn't be any fuzz.

Can't find any info at all on that either! (not being much help am I?) I would expect the sensor just a simple thermistor type only - resistance between two terminals, no "active" components or bridge.

I'll just measure the resistance, and then I'll probably find the value... It would of course be nice if you could find the value of the resistance in the documentation. I found it in the corolla documentation in the diagnostics section. It said that the resistance should be 2700 ohm at 25 celsius. It might be the same on the rav.

Hope you can help me! I really appreciate it!

Cheers

[Robert6920]

Lord, I must be thick! This means nothing to me at all! It might as well be written in hieroglyphics!!

All I can say is, I take my hat off to your techie guys, and good luck with your project

[bitman]

interesting stuff since after i sold all my kenwood gear i'm building my own ice / carpc. but i have a 2001 petrol and can use the obdii bus for this info. have a look at here may be you can get some useful info there.

[Fujisan]

Lord, I must be thick! This means nothing to me at all! It might as well be written in hieroglyphics!!

All I can say is, I take my hat off to your techie guys, and good luck with your project

Whooosh!

Straight over my head, the lot of it!

Come on......we'll get our coats.......and head off down the pub!

[St Thicket]

interesting stuff since after i sold all my kenwood gear i'm building my own ice / carpc. but i have a 2001 petrol and can use the obdii bus for this info. have a look at here may be you can get some useful info there.

Thx for the link. Doesn't help me much, since my diesel doesn't support obd2... i have an ELM327 for sale though... :-)

Fujisan... you're being really helpful! Why do I even bother doing this? Once a geek, allways a geek!

[Fujisan]

Fujisan... you're being really helpful! Why do I even bother doing this? Once a geek, allways a geek!

What's the OBD code for sense of humour failure!

Just having a little joke........lighten up!

[bitman]

interesting stuff since after i sold all my kenwood gear i'm building my own ice / carpc. but i have a 2001 petrol and can use the obdii bus for this info. have a look at here may be you can get some useful info there.

Thx for the link. Doesn't help me much, since my diesel doesn't support obd2... i have an ELM327 for sale though... :-)

on that forum they NOT only talk / write about odbii interfaces... if you are a geek then you will search a bit more on that forum and find lots more info's

the same goes here what is more pointed to the uk.

[bitman]

pport obd2... i have an ELM327 for sale though... :-)

does that ELM327 interface has a USB connection? if so what do you want to have for it?

[St Thicket]

What's the OBD code for sense of humour failure!

Just having a little joke........lighten up!

Yeah, i got it... but I just had to comment it :)

I know this tech stuff can be quite hard to understand for "technically challenged" people.

But you kow, there are 10 types of people... the ones that unerstand binary, and those who don't :D

Just bare with me, and my norwegian sense of humor...

[St Thicket]

pport obd2... i have an ELM327 for sale though... :-)

does that ELM327 interface has a USB connection? if so what do you want to have for it?

This is the same one that I have

It might be easier for you to order directly, because I'm located in Norway, so then you have the customs clearance and stuff...

[Fujisan]

What's the OBD code for sense of humour failure!

Just having a little joke........lighten up!

Yeah, i got it... but I just had to comment it :)

I know this tech stuff can be quite hard to understand for "technically challenged" people.

But you kow, there are 10 types of people... the ones that unerstand binary, and those who don't :D

Just bare with me, and my norwegian sense of humor...

101111011011010101001001010000011111

Good man I'll leave you in peace then :D

Good luck with your project

[bitman]

pport obd2... i have an ELM327 for sale though... :-)

does that ELM327 interface has a USB connection? if so what do you want to have for it?

This is the same one that I have

It might be easier for you to order directly, because I'm located in Norway, so then you have the customs clearance and stuff...

thx, just bought one for my ice project. B)

[local hero]

pport obd2... i have an ELM327 for sale though... :-)

does that ELM327 interface has a USB connection? if so what do you want to have for it?

This is the same one that I have

It might be easier for you to order directly, because I'm located in Norway, so then you have the customs clearance and stuff...

thx, just bought one for my ice project. B)

Well Ole Solskjaer, is my hero and one of the nicest people it has been my pleasure to meet, but for someone who only learned how to switch a computer on 6 months ago, this is far too much for me to understand, but good luck with it though..

[bitman]

well got my odbii kit today....

only £24 B)

[St Thicket]

Nice!

seems like it's working :-)

[St Thicket]

I finally did some tinkering yesterday, and learned a lot more about the connector.

The "Fuel Cender Signal" pins were not connected, neither was the engine type pins, except the engine version 1 pin. This tells me that for fuel, i need to use the "injecter voltage" and the "injecter drive signal" (pin 14 and 15). This again tells me that i need to time the "injecter drive signal" and calculate the volume from it. My toyota dealer told me that for every combustion, the nozzle injects about 5 times, so this could be quite interesting to view on a oscilloscope...

I also measured the resistance between the "outside temperature signal" pins, and it was about 1.7k ohm. This is great, because then it seems like it is a NTC thermistor that I can use! The temperature was less than 25 celcius, so I guess the resistance at 25 degrees would be about 1.5k. I'll try it out, and see if it's correct.

For reading the temperature, I'll use a Microchip PIC controller, and some 7-segment displays. Havent decided to use a decimal or not... If anyone have experience with measuring temperature with NTC, please let me know. I'd appreciate some hints and tips, since I only have experience with pt100.

[shcm]

The "Fuel Cender Signal" pins were not connected, neither was the engine type pins, except the engine version 1

Opps, sorry should have said only pin 15 was connected.

I also measured the resistance between the "outside temperature signal" pins, and it was about 1.7k ohm. This is great, because then it seems like it is a NTC thermistor that I can use! The temperature was less than 25 celcius, so I guess the resistance at 25 degrees would be about 1.5k. I'll try it out, and see if it's correct.

After a bit more digging, I've found this on at least one ambient temp sensor on the 4.2:

Seems to tie in with what you measured, if the temp was close to 25C at the time. For your climate though, I expect you want resistance values for below 10C! I think you could extrapolate that graph back below 10C with a bit of curve fitting.

For reading the temperature, I'll use a Microchip PIC controller, and some 7-segment displays. Havent decided to use a decimal or not... If anyone have experience with measuring temperature with NTC, please let me know. I'd

I'm sure you know, but in analog days the trick was/is to use a fairly linear part of the response curve only, or some compensation circuit for wide temperature ranges. With the PIC why not just have a small simple look up table and you can interpolate between the table points for other values.

Which PIC will you use? Assembler or C?

For the display, how about driving a single line dot matrix off the PIC: ?

http://uk.rs-online.com/web/search/searchB...t&R=5326335

Maybe a bit more expensive, but perhaps a more pleasing result?

appreciate some hints and tips, since I only have experience with pt100.

Platinum film based devices are an expensive extravagant luxury!! :D

Have fun!

Cheers

[St Thicket]

Thank you so much for the reply!

Opps, sorry should have said only pin 15 was connected.

That's OK. I figured it out anyway :)

After a bit more digging, I've found this on at least one ambient temp sensor on the 4.2:

Sweet!

Seems to tie in with what you measured, if the temp was close to 25C at the time. For your climate though, I expect you want resistance values for below 10C! I think you could extrapolate that graph back below 10C with a bit of curve fitting.

I'm sure you know, but in analog days the trick was/is to use a fairly linear part of the response curve only, or some compensation circuit for wide temperature ranges. With the PIC why not just have a small simple look up table and you can interpolate between the table points for other values.

If I use a microcontroller, shouldn't it be possible to insert the exact 3rd degree formula, and get the perfect reading? I'm going to try anyway

Which PIC will you use? Assembler or C?

For the display, how about driving a single line dot matrix off the PIC: ?

I'll program in C, since I already have all development tools available. For PIC, I havent decided yet. I have a box full of various samples, like 16F84, 16F628, 16F877, 18F2550 etc. I think a 16F628 will be sufficient.

For display, I'll use 7-segment, due to the excellent readability in the various light conditions in a car. I allways hated the original stereo because of the LCD-screen and that terrible yellow/amber color. Horrible

Platinum film based devices are an expensive extravagant luxury!! :D

I know :)