map sensor wiring

[N_Jonesy]

hi does any body know what the 3 wires on the map sensor are and in what order
also what number pins they go to on the ecu plug
earth
feed
supply to ecu

thanks

 

[MicKPM]

You should be able to work these out easily with the aid of a multi-meter.

Earth will be common and go to ground all the time.
Feed is a switched voltage that comes on with the key via the main control relay
Process of elimination leaves the line back to the ECM... DMM continuity test function will help you trace this back thru the loom to the ECM

Mick

 

[N_Jonesy]

thanks mick

 

[N_Jonesy]

pin a = green earth
pin b = purple feed to ecu
pin c = +5v

earth is fine
measured ohms at 2k between pin b + c with ignition off and got 0.00 so all good
engine idling and probing pins a + b gives a reading of 1.6v (should be +4.3v)
engine at 3000 rpm and probing pins a +b gives a reading of 0.00 (should be +4.1v)
all the above points to a faulty map sensor can anybody confirm what i have checked is correct and is there anything else that could cause the incorrect readings

thanks guys

 

[MicKPM]

Search is great ;-)

http://www.cliosport.net/forum/showthread.php?p=7211100

 

[N_Jonesy]

thats where i found the info to test the map sensor from your previous post

engine idling and probing pins a + b gives a reading of 1.6v (should be +4.3v)
engine at 3000 rpm and probing pins a + b gives a reading of 0.00 (should be +4.1v)

does that seem to point at a dodgy map sensor
thanks

 

[MicKPM]

Could be then yes but I'd like to confirm it by seeing what the ecu is seeing to in the live data screen.

 

[N_Jonesy]

ok thanks mick looks like i will have to try and find a local garage that has the ability to do this
pity your 160 miles away

 

[MicKPM]

You want to be sure of two things before that sensor is replaced. Firstly, that the ecu is seeing actual "atmospheric" pressure when the engine is off (normally around 101kPa) and then a slight vacuum when running at idle (as an NA engine creates this when breathing).

If you're not seeing atmosphere correctly then the base reading is wrong and the sensor needs replacing

 

[N_Jonesy]

No idea how to go about checking the above mick so I will have to either have to get a new map sensor and try it or find a local specialists
Thanks

 

[Sean6545]

Get it on a diagnostic machine and read the live data being fed to the ecu.

Like mick said, 1000mb approximate with the engine off.

 

[N_Jonesy]

Any idea if I can check live data with a cheapo ebay diagnostics machine, Im guessing I would need a more advanced one as found in a garage?
thanks

 

[Sean6545]

It's unlikely a generic eobd reader will do that.