GM 3 Bar MAP Install

**NOMIEZVR4** · 10-31-2013, 10:42 PM

So I've got a MAP sensor on the way...I've been looking around for an install tutorial, didn't find one so thought I'd start a thread. Its got 3 wires, Power, GND and signal wire. Finding Power and GND shouldn't be an issue, but where to tap for the signal and more importantly, how do I hook it to my ECU harness so I can log boost? I'm assuming PIN 93...can someone fill in the details?

Thanks! I can take pictures when installing mine so others will have a guide to help in future installs

**llabmik2** · 10-31-2013, 10:46 PM

Just make sure you hook it up to a +5v not a +12v......i've seen it done.

**mjannusch** · 10-31-2013, 10:54 PM

You can get +5v off the TPS/sensor power wire (I believe it is a green wire with a yellow stripe), ground is any one of the grounds at the ECU, and if you've got a wire already on pin 92 (not 93 - that's set up for wideband input in Chrome) then cut it and splice the MAP output wire to the wire going into pin 92. Depending what harness you have, you might need to add a lead into pin 93's location.

Sorry I don't have more detail on the +5 power, I used the 0-5v output from my PLX Devices vac/boost sensor module so I didn't have to hook up +5v this time around.

I recommend that you put in the general GM sensor specs for voltage and pressure in Chrome, and then double-check it with some sort of an air source with a boost gauge hooked up that's known to be accurate - you may have to adjust the values a bit in Chrome to get it to match. Once it is set up, you should be good to go.

**kywhitelightning** · 10-31-2013, 11:02 PM

Use the MAF 5V source and GND. Send your signal to PIN 92. I installed mine under the fuse/relay box on the PS. There's a captured nut on the fuse box bracket that works perfectly to mount it. Once installed use a pressure pump to validate the readings through Evoscan. I amended mine a little because the defaults seemed to be off just a hair.

One other thing, I bought a cheap ebay knockoff earlier this year and it failed within a few months. First it leaked and then anytime I went into boost it would peg the log. Buyer beware. The real OE part numbered sensor hasn't let me down yet though.

This should be a great how to. Thanks Nomie!!

Jeff

**NOMIEZVR4** · 10-31-2013, 11:13 PM

wow, quick responses! Thanks guys!

Jeff I really wanna see my boost curve on VD!!..can't wait

Thanks for the heads up...I actually purchased an EBAY unit(after reading online reviews) but I'll just keep it because the pigtail from GM is $30 anyways...so I'll just order a MAP sensor from NAPA..cross referenced the part number actually costs almost $100 less than the GM Dealer...I'll post all details here...Oh yeah...I forgot to mention...the EBAY Sensor I got comes with a 2 year warranty!...so I guess I'll hold off on getting the napa part for now..

http://www.ebay.com/itm/321237632879

Thats the link for the sensor I got in case anyone else is interested.

**kywhitelightning** · 11-01-2013, 12:11 AM

Yep, that's the cheapo I was referring to. Unfortunately the pigtail for the one I have now is different than the one shown in the image. It doesn't take much to get it to work (5 minutes and a jewelers screwdriver to knock off the aligning notches) but, they definitely are different. Here's the one I have now. It's even a little cheaper than the price you quoted from NAPA.

GM 3 Bar Map Sensor - Modern Automotive Performance

Jeff

**99 vr4** · 11-01-2013, 11:15 AM

Originally Posted by mjannusch

You can get +5v off the TPS/sensor power wire (I believe it is a green wire with a yellow stripe), ground is any one of the grounds at the ECU, and if you've got a wire already on pin 92 (not 93 - that's set up for wideband input in Chrome) then cut it and splice the MAP output wire to the wire going into pin 92. Depending what harness you have, you might need to add a lead into pin 93's location.

Sorry I don't have more detail on the +5 power, I used the 0-5v output from my PLX Devices vac/boost sensor module so I didn't have to hook up +5v this time around.

I recommend that you put in the general GM sensor specs for voltage and pressure in Chrome, and then double-check it with some sort of an air source with a boost gauge hooked up that's known to be accurate - you may have to adjust the values a bit in Chrome to get it to match. Once it is set up, you should be good to go.

Originally Posted by kywhitelightning

Use the MAF 5V source and GND. Send your signal to PIN 92. I installed mine under the fuse/relay box on the PS. There's a captured nut on the fuse box bracket that works perfectly to mount it. Once installed use a pressure pump to validate the readings through Evoscan. I amended mine a little because the defaults seemed to be off just a hair.

One other thing, I bought a cheap ebay knockoff earlier this year and it failed within a few months. First it leaked and then anytime I went into boost it would peg the log. Buyer beware. The real OE part numbered sensor hasn't let me down yet though.

This should be a great how to. Thanks Nomie!!

Jeff

In order to get accurate readings, you must hook the sensor up correctly. Unfortunately, everyone seems to think that you just need power and ground and you have a signal. This is not the case.

The sensor needs 5V DC. The sensor also needs a proper ground reference, as the sensor output is relative to this ground. Therefore ALL sensors share a SENSOR GROUND, this is NOT CHASSIS GROUND or BATTERY NEGATIVE!

To clarify, DO NOT HOOK ANY MAP SENSOR GROUND TO CHASSIS GROUND. THIS WILL SKEW THE OUTPUT!

In order to get correct readings, any MAP sensor must get voltage from pin 42 on the 98/99 ECU (pin 61/81 on the 91-97 ECU). This is +5V for the sensors. This is available at various points under the hood. Sensor ground is available from pin 49 on the 98/99 ECU (pin 72/92 on the 91-97 ECU). Again this is available at various points under the hood. The MAP sensor input is pin 92 on the 98/99 ECU (pin 74 on the 96-97 ECU, the only years with a factory MAP sensor).

The MAF +5v (pin 1 on the MAF - should be Green with Yellow Stripe) and Signal Ground (pin 5 on the MAF - should be a black wire) as Jeff mentioned above will work fine. You can also get it closer at the TPS: Pin 1 (again green with yellow) and Pin 4 (black wire).

All of the Clone PnP harnesses have a Yellow (+5v) and Green (+0v) pigtail along with the MAP sensor input pigtail to facilitate the addition of a MAP sensor.

Now for the TECHNICAL BLABBER:

In all vehicles, measuring voltage at different points around the vehicle will yield different voltages due to supply voltage losses due to wiring and ground losses due to vehicle construction. If you were to then measure those same voltages around the vehicle using the same ground point (like the battery negative terminal), you would see a completely different set of results, sometimes more than .1 volt! This is why ground kits help.

Now for most things, this is not an issue; Things like light bulbs, wiper motors, switches, etc. But for things like O2 sensors, throttle position sensors, MAF Sensors, and the MAP sensor, to name a few, which work on tenths (and sometime lower) of a voltage, changing the output from .4 to .5 volts IS significant. So in order to fix this issue, there is a separate ground for all of the sensors, which is referred to as signal ground. All reference systems in the car responsible for engine managements share this common ground which is NOT tied to chassis ground. In fact, if you measure the voltage on this line as referenced to chassis or battery ground, you will see that it is NOT 0.000V! But that is ok, because all of the systems are using this as the signal ground, so they are all in synch in relation to each other.

**NOMIEZVR4** · 11-04-2013, 03:29 PM

Is this correct? EDIT: YES
A-GND goes to pin 5 of MAF Harness
B-Signal goes to Pin 92 of ECU Harness
C-5V goes to Pin 1 of MAF Harness

That's all there is to it as far as the Hardware setup goes. I'll probably T the Line from the BOV and run it to the MAP Sensor.

**NOMIEZVR4** · 11-04-2013, 04:06 PM

Verified online...its OK. Map Sensor is wired in..Pictures to follow shortly.

Next Step is to figure out what settings need to be changed in EVOscan and ECUflash(if any?)