After looking around it looks like this is the place to ask this. Throws code p0107 map low voltage. ok. So checked everything and yes bought not one but 4 map sensors. You wouldnt believe why but it was necessary. So here is the issue. Map sensor has 4 wires. 5v power refernce, ground, signal. the other not sure but i think its signal for IAT ? anyway doesnt matter. No nothing on signall wires.

Unplug sensor I have good 5v reference. Good on ground. Plug sensor in and backprobe and I no longer have 5v, it drops to 1.8v. ( I assume this is why I get nothing out of signal wire)
Why do I have a voltage drop when i plug sensor in and not when unplugged? Ive also unplugged all other sensors other then cps to see if they had any effect but no change.

to me this is still saying bad sensor but what the hell how is that possible ive bought 4 and they all read the same. (one went back, have original here and 2 others)

any ideas??

 

Sounds to me like an issue with the wiring or female connector. It’s the only two constants. IDK... just spitballing here.

 

would be nice if we knew what car we were discussing here......you do know that the supercharged engines have two MAP sensors...one is T-Map sensor

Bryan

 

Thanks for response. Sorry it’s an 03 base Cooper. Yea I knew the s has the TMAP.

ok more clear I thought connector possible too but no. I actually ran jumpers from connector to sensor. Just the 5v and ground eliminating the signal wire. Still same voltage drop.
I also jumped the refernce to the signal and checked live data and that worked it showed the 5v on the signal. (Jumped on connector not plugged in)
wondering this....... when I plug this in is it somehow connecting the circuit that everything on that same 5v is on and if the crank sensor is on that 5v and is going bad possibly causing the drop on the map? Only day that cause I found a thread where someone had the same drop on voltage when plugged in and another sensor caused it. I also do not have a crank sensor code showing.
I’m on a mission to solve this now. Not giving up

 

One more thing ... I said drops to 1.8. Today when I was trying things the drop was at 2.4

hey 2.6 more volts and I’m there!!!
so at that rate if I wait a week it will have fixed itself!!!! Lol

 

Surely once it is connected the voltage is variable as it reads what it is supposed to read? 5 volts constant would be a fault as it would mean the circuit is shorted so I do not know why that is your target.

 

To clarify. The 5v reference wire is the (feed) to power the sensor. It as far as I have read remains constant. It’s the power. The signal wire which is the return wire to the computer gets no signal or in other words no voltage which is variable back to computer.

My issue sue is the 5v feed drops to 1.8-2.4 when I plug the sensor in. With nothing coming out of signal wire. I’m thinking no signal due to lack of full 5v input when I plug it in. But idk.

It shouldnt drop on plug in thats that’s what I think the issue is. And there is no way I got 3 bad map sensors I would think

and if and when I figure this out I will put it up. Or a picture of the car on fire. One of the two

 

Just an update. After unplugging everything and I mean erverything I still had the drop in v when plugged in.
So to check the new sensor I cut the map 5v refernce and tied it to the tps 5v. That kinda worked. I did retain the 5v going in when I plug it in but still no output on signal wire.
if someone can double check me on this schematic. It is the non s. 4 wires.
brn/wht is ground yel/blue is 5v ref. Other 2 are signal correct?

 

Solution!!!!
here is what I did. I tied the voltage drop line to the 5v tps line. Got my continuous 5v. But it threw an iat high code. So I looked again because that told me the power on the dropped volt line was the power for a 2 wire iat sensor and it was a resistance sensor. So I looked and realized the the map portion of the sensor had its own power 5v not shared power with the iat. (Map and iat are one sensor) I was right. No power to map side of sensor. No power on line at ecu. So it’s prob ecu not putting power out at that terminal. I tied the 5v for map side to the tps 5v an viola it worked. All codes gone map sensor works. Live data on scanner shows correct. So now I’m golden!!!!

 

Runs perfect now I ended changing/splicing a new plug! Went to the junkyard found a good condition plug! But a new one from parts geek will work also! The plug was worn out corroded not making contact. Solder may not fix this because the contacts are brittle after the age. Best to change this plug splice a new one !