MAP sensor trouble

vroomevo · Jan 6, 2007, 01:15 PM

Hello,
i just installed GM MAP sensor today.
problem is, it is not reading the boost.

made sure it is getting 5volt(not 12 volt) power supply, vacuum hose is well connected to nipple on the MAP sensor, grounded on top of manifold with other bolt.
made sure output from MAP sensor is connected to group C yellow wire(MAP sensor input) on the ECU+.
selected GM MAP sensor with ECU win program.

1)did i get a faulty MAP sensor from gmdirectparts.com?
2)i read somewhere that MAP sensor cannot be grounded to chasis, has to be grounded with other stock sensors, is it really true? should i change ground?
3)am i not supposed to get some voltage from MAP sensor while the car is in idle? i am not getting any voltage from MAP sensor.

Chong

burgers22 · Jan 6, 2007, 03:15 PM

Hi

My MAP sensor is grounded to the earth bolt near the strut brace central fixing, no problems there. Silly question, did you enable the GM MAP sensor in the ECU+ win sofware?

MB

vroomevo · Jan 6, 2007, 06:49 PM

yeap. i did enable the MAP sensor in the ECU+(GM MAP 3.0 bar).
don't know what's going on. if this is the faulty sensor, there is no return with gmdirectparts.com.

burgers22 · Jan 6, 2007, 11:51 PM

Hi

As a test, I guess you could hook up a foot pump to the MAP and gently give it a few PSI to see if the voltage on the output leg changes.

MB

tlcoll1 · Jan 7, 2007, 11:34 PM

With the MAP sensor connected to atmosphere, you should see a voltage on its output, even when not connected to the ECU+. I'd start there, with the nipple open and just the power supply wires connected.

Tom

vroomevo · Jan 8, 2007, 05:05 PM

thanks for the reply. i will try that tonight.
Chong

vroomevo · Jan 9, 2007, 10:47 AM

so, i bought a new electic tester with voltage reading.

MAP sensor does produce voltage, around 1.5(close to 2.0 i think) when ignition is on.
then voltage drops around 1 when the car is in idle.

ECU+ still read boost as 0psi.

give little boost while in idle, ECU+ still read boost as 0psi.

double checked the wire going into ECU+, it's the yellow wire in group C.

hmm...

vroomevo · Jan 11, 2007, 01:23 PM

it is finally reading, still shows 0psi at idle, and at wot, it reads about 5lbs less than my boost gauge.

with map sensor, wether, humidity, temp etc all factors in but i should not increase boost depending on MAP pressure correct?

mad_VIII · Jan 12, 2007, 07:10 AM

Quote:

Originally Posted by vroomevo

it is finally reading, still shows 0psi at idle, and at wot, it reads about 5lbs less than my boost gauge.

with map sensor, wether, humidity, temp etc all factors in but i should not increase boost depending on MAP pressure correct?

older versions of the software don't read vacume, only boost. depending on the gauge you are using, it will read a few psi lower than gauge pressure. If i were you, I would base boost adjustments on what your gauge was reading with the car stock qnd use that to determine the offset to run. for example, if your gauge was reading 18psi peak with the car stock and the map sensor only reads 14psi when the gauge reads 18psi then assume you have a 4psi offset from the gauge and determine your target boost from that (if you want to run 20 psi, target 16psi on the map sensor).

I checked my defi gauge against the local reputable dyno shop (www.dyno4mance.com) and found that it reads dead on with the dyno map sensor, while my 3-bar map sensor reads 2-3 psi lower, so I target 19psi on the map sensor if I want to run 21-22 psi.

burgers22 · Jan 12, 2007, 10:07 AM

Quote:

Originally Posted by vroomevo

it is finally reading, still shows 0psi at idle, and at wot, it reads about 5lbs less than my boost gauge.

with map sensor, wether, humidity, temp etc all factors in but i should not increase boost depending on MAP pressure correct?

Hi

The MAP sensor has no direct affect on the operation of the actuator/wastegate. I have read that a MAP setup wouldn't be able to react quickly enough to form part of a closed loop boost control sysytem ( not the MAP itself, but the whole system).

MB