Map sensor reading 27psi while key on engine off

moenning1

New Member
Joined
Mar 25, 2013
Just installed power logger and my map sensor is reading 27psi with key on engine off? I replaced with another map sensor getting same reading? Not only that the car pops and backfires and won’t start. Has new fuel system just installed, injector harness, turbo, Down pipe, maf, I have a accufab adjustable fuel regulator seems like it dosent hold pressure either? Took fuel rail and injectors out of intake and checked for leaking injector, no leaking injector. Any ideas? I have a crank sensor and cam sensor ima install today.
 

Jerryl

Tall Chinese Guy
Joined
Dec 14, 2004
Just installed power logger and my map sensor is reading 27psi with key on engine off? I replaced with another map sensor getting same reading? Not only that the car pops and backfires and won’t start. Has new fuel system just installed, injector harness, turbo, Down pipe, maf, I have a accufab adjustable fuel regulator seems like it dosent hold pressure either? Took fuel rail and injectors out of intake and checked for leaking injector, no leaking injector. Any ideas? I have a crank sensor and cam sensor ima install today.
Wiring issue if you have a true 3 bar MAP and selected that in the PL software. Likely using the 5V signal to feed the MAP input. What chip are you using and do you have alky?
 

moenning1

New Member
Joined
Mar 25, 2013
Wiring issue if you have a true 3 bar MAP and selected that in the PL software. Likely using the 5V signal to feed the MAP input. What chip are you using and do you have alky?
It’s a true 3 bar map, no alky, tt5.7 chip that will be replaced soon due to new upgrades. 3 bar is selected in pl software. I am running a 5v signal from ecu.
 

Jerryl

Tall Chinese Guy
Joined
Dec 14, 2004
KOEO, measure MAP wire voltage to/at the PL.
What position on the PL is THIS wire connected?
 

Jerryl

Tall Chinese Guy
Joined
Dec 14, 2004
Sounds like it's a 5V (4.999) wire, minus some voltage drop. Let us know what you find.
 

moenning1

New Member
Joined
Mar 25, 2013
Sounds like it's a 5V (4.999) wire, minus some voltage drop. Let us know what you find.
Ok, it’s reading 4.40v at pl analog, 4.70v at sensor, I checked my wiring and it’s correct, grey/black wire to pin c14 (5v) tps, then tee off map green wire to #2 on analog. Shouldn’t it be reading around 1.6v? Possibly bad ground?
 

Jerryl

Tall Chinese Guy
Joined
Dec 14, 2004
I figured out that ctrl b resets the attitude bars on pl now it’s setting around zero with koeo
That's a great find, but still need to verify the ~1.6V KOEO with a 3 bar MAP. Calibrating/setting zero at 4.7V input is basically telling the software that atmospheric is 27 PSI.
 

moenning1

New Member
Joined
Mar 25, 2013
That's a great find, but still need to verify the ~1.6V KOEO with a 3 bar MAP. Calibrating/setting zero at 4.7V input is basically telling the software that atmospheric is 27 PSI.
Correct, I’m kinda stumped on how the 3 bar is putting out the same volts as the supplied power I have 2 3 bar map sensors and both our reading the same
 

moenning1

New Member
Joined
Mar 25, 2013
That's a great find, but still need to verify the ~1.6V KOEO with a 3 bar MAP. Calibrating/setting zero at 4.7V input is basically telling the software that atmospheric is 27 PSI.
If i wasn’t getting ground I wouldn’t be getting power
Verify this at the MAP plug
A=ground
B=signal
C= 5v
grey wire 5.03v a
Green wire 4.70v b
Ground wire - issue lol
I just ran a small wire off the ground post on battery and stuck it in the connector with probe and bam, 5.03v c, 1.57v b, but I don’t know where the map sensor is grounded?? Looks like I need to invest in a ground stretcher kit lol.
 

moenning1

New Member
Joined
Mar 25, 2013
Verify this at the MAP plug
A=ground
B=signal
C= 5v
I’ve tried looking up wire diagrams and seen if anyone else has had this issue and couldn’t find anything, but now I’m 100% positive it’s a grounding problem which I figure i wouldn’t get power out but looks like I’m wrong, now I just need to know where the map gets it ground from?
 

Jerryl

Tall Chinese Guy
Joined
Dec 14, 2004
"The map gets its power and ground through that connector from the dash harness tach boost module , you need to run a wire from the tps gray at ecm (pin C14) to pin B (gray) at that connector that will provide 5v to the map connector underhood then you need to connect the ground on that connector (G blk wire ) to the tps ground at ecm (pin D12 blk) with 5v at gray wire at map connector and ground at blk wire of map connector the center pin B green wire will have the map signal which for a 3 bar map should show 1.6v key on engine off"
 

moenning1

New Member
Joined
Mar 25, 2013
"The map gets its power and ground through that connector from the dash harness tach boost module , you need to run a wire from the tps gray at ecm (pin C14) to pin B (gray) at that connector that will provide 5v to the map connector underhood then you need to connect the ground on that connector (G blk wire ) to the tps ground at ecm (pin D12 blk) with 5v at gray wire at map connector and ground at blk wire of map connector the center pin B green wire will have the map signal which for a 3 bar map should show 1.6v key on engine off"
Perfectly said thanks man your help was much appreciated I don’t why the site has me as a new member been on here for al most 10 years lol. I seen you live in Houston I live in San antiono
 
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