Here's one for ya.....

Honda MAP sensor.

In my (limited) experience, most MAP sensors are pinned so that the middle pin is the SIGNAL. Everything that I have looked at regarding Honda wiring suggests that this is the case.

However, I mailed Omnipower, the makers of the MAP sensor in question and they came back with a pinout as per my picture.......



So, what would you do? Trust the makers? Even against all the other investigations I have done to find out the pinouts? (not that any of those were really conclusive).

I asked RickyLee on here, who kindly gave me what he thought was the correct pinout and it wasn't what Omnipower suggested either.

 

Can you not just test it to see?

RW

 

dont believe that for one second

 

As per Steven RW, I would test it before connecting it to an ecu, not guess.

I would imagine that a resistance meter across each pair of pins and compare that to a known one should reveal which is which, but Ive never tried doing so which means I cant tell you what sort of resistance to expect to indicate you are on say ground and +ve for example.

 

Yep, makes sense to me - get 5 volts, an earth and something that can read the output signal. Stick a pipe on the end of the vacum nipple and suck/blow to see which pin gives a variable reading? Id do that with a crappy old one first so I had an idea of what range I expected to see. Is there a worry that it might blow it if you put the 5volts in the wrong one?

RW

 

I wouldnt put 5v in it straight away, I would just use a resistance meter to measure the resistance between the pins, I would imagine from that alone you would be pretty confident which was which.
5v is unlikely to blow anything, but I still wouldnt risk it on a part with any value.

 

FYI....

You cannot use a resistance meter to check/test a map sensor in any way !

5 volts is perfectly capable of blowing up the map sensor if its connected up wrong as most ECU's will provide several amps @ 5 volts which is enough to start a small fire..LOL

If I was investigating an unknown sensor like this, I would test the sensor using a volt meter on the output.
Supply the 5 volts power through a 1K resistor temporarily as then if you do connect it up wrong, the current drawn will be limited and should not damage the sensor.

 

A man that knows what he is talking about!!

 

Now i'm no electronics expert so Simon will have to correct me, but for a start couldn't you just turn the car on and see which pin on the loom plug gives 5v potential when you put your meter between it and earth?

 

I wouldn't bother using that actual map sensor, they are prone to splitting in half after a few hundred miles on FI hondas - the reason i dont use it.

 

Doug,

The issue was the sensor not the loom configuration.

 

for what it's worth (which is jack shit really!) 3 bar cosworth ones still work in the engine at idle after wiring them backwards with +5 and signal wires reversed. still work properly when corrected too!

 

Hurrah, sounds exciting.

Thanks for your help Doug etc. I'm scared to connect any power to it, because I simple don't want to fry it.

 

Simon, some good info there, but where you said "I would test with a volt meter on the output" the problem here is that he doesnt know with enough confidence which is the output in the first place by the sounds of it.

 

If you find which car its designed to plug straight into, then that sounds reasonable to me as im sure you can find a wiring diagram for whatever car it is Christian?

 

Thats fairly simple and it's not that hard to find wiring colours and even ECU pins that they connect to. But I cannot decipher that into the info I need!!

I have the test procedure on Autodata, perhaps if I post that, someone more technical than me might be able to work out from that which pin is which.

 

Im sure Mr Johnson will be able to help you out

 

Here are the test procedures for the MAP and TPS. Of course these assume that the components are plugged in, but I'm sure they its possible to tell which pin is which.

For the MAP, I think that......

1 - 5v
2 - Earth
3 - Signal



For the TPS, I think.....

1 - Earth
2 - Signal
3 - 5v

 

Unfortunately those test procedures are not aimed at working out the wiring configuration of the MAP sensor, they rely on you already having it wired the correct way round first.

 

Of course, but if that were the case, I wouldn't even be posting this!! LOL.

Surely the combination of testing across certain pins may give a clue as to what pin does what!!

 

Yes if you have another one to compare it to, otherwise you wont know what results you are supposed to see.

You can try checking resistance, but Simon seems to think that wont yield any gains, but you could also try checking voltage, Ive never needed to work out the pin configuration of a MAP sensor as I have always believed what the manufacturer tells me, but on for example a crank sensor if you put an osciliscope on it you can see the value changing when you pass metal pass it, so possibly you will get a similar effect if you vary the pressure going into the MAP sensor.

Ultimately one of the pins is going to change either voltage or resistance when it sees a change in pressure, so its a case of seeing how you identify that, which if you have a known configuration sensor in front of you, you can try looking for both resistance changes and voltage changes on that across the sensor pin in circuit with each of the other two pins to see what change occurs, then look for the same change on the sensor you have.

I personally would be talking to the manufacturer though, if they give you incorrect information in writing in an email that leads to you connecting 5v across it and that damages it, thats their liability IMHO in terms of replacing the sensor, but obviously I would be NOT using an ecu to supply the 5V I would be using a straight 5v dc supply to do so. (with a very low value fuse on it preferably to limit your chances of blowing the sensor)

 

Chip, as per my original statement, I have spoken to Omni, who made the sensor and they came up with the pinouts as per my picture. I'm with you in one sense that if I try it and they told me wrong, it'll be their liability, but since they are in the US and I'm not a gambling man.......

Do I trust the person I spoke to or not??!!

 

Try sticking a scope on it and varying the pressure and see if you can detect any form of output, Ive no idea if it will work or not, but it wont damage anything to try.

Then if that doesnt work, and Simon cant come up with anything, put 5v across the pins they have said, with a low value fuse on the +ve, and see what happens as you dont really have any alternative.

If you do kill it, then at least you have in writing from them that diagram to prove you didnt do anything they hadnt told you to do.

 

Christian,

are you deliberately trying to get Chip to bite or something, as going by the thread title that is what you want. Maybe if you asked him about overpriced bath panels and mortgages he would be able to help you better

 

Go back to sleep Rich.

 

I cant go back to sleep. This is obviously a carry on thread from the rr one where you claim chip to know it all. Entertaining in its own little way really mate

 

Rich, it also struck me that rather than truely wanting my opinion Christian was just engaging in some sort of childish "get internet revenge" thing with this thread by trying to show I dont know everything (which would be pretty pointless as if he wants to show that he only needs to ask me if I know everything and I'll reply "no I dont" as ive never claimed that anyway)

But I decided to instead just take it at face value that he wants my help, so I think you should do the same.
If he does want my help then its just a shame I cant give him any beyond a few guesswork suggestions as I have never been in the situation he is now so have no experience of how to find the pinout on a map sensor sadly which is a shame as I would of course help him out if I could.

 

I would go by the manufacturers information but only if they provide it in a proper format of a PDF file or printed drawing etc... (I.E. not verbal)
Then, that way you have some come back if its wrong.

Besides there are 2 things here...

1) I would use a known sensor such as the Bosch 4.6 bar one if there was any doubt.
2) I would never consider touching a Honda

 

It might be worth asking on: http://www.honda-tech.com/

 

Chip, 1 word. Banter.

Chill out people.

Doug - Thanks for your help.

 

what car does it come from?

find that car, get under the bonnet to find the wire colours

job jobbed

 

Wrong thread...PMSL

 

Did you reply on the wrong thread per chance??

 

BOLLOX... Yes