Since I got my PS2K a few years ago, AVI #9 (MAP Sensor input) has behaved rather oddly in that it hovers around 4.5-4.75v. Since I was a N00b to standalones back then, I didn't think too much of it.

Now that I got my 20B-REW powered FC running, this has become a problem as I'm cleaning up the mess of vacuum lines. Bought a GM 3-bar Map sensor, wired it per Haltech and the seller's instructions (A: Ground, B: Signal, C: 5v+), reconfigured the input using the calibration file included with ECU Manager v1.11.1 and gave it a crank...Didn't start. ECU Firmware is 1.09.2, Rom Version 3.

Before hooking up the GM Map sensor, I double and triple-checked its pinout before making any connections, as well as turning the main breaker off per my standard safety measures. Untill this time, there was no sensor EVER connected to my PS2K since I had purchased it new from Defined Autoworks and was the first person to open the box. So we can rule out mishandling after delivery and I HIGHLY doubt something went screwy at the shop.

I didn't have the laptop out there with me when I tried starting it, so I don't have any pertinent data other than the car behaving strangely like it wanted to start but couldn't for some reason. This was 2 days ago (4/22/13), and I had a job interview early the next day so I couldn't really delve too deep into what was going on.

The next day, I pulled every single relay and did a through test. All passed with flying colors on coil impedance and continuity at rest and energized as they should. Also checked the sensor wiring for continuity, 0.03 ohms between Connector and Ground, 5v and ECU as they should be.

For the sake of comparison, the Platinum Sport 2000's internal pressure sensor worked just peachy to get the car started up with, even when using pet store silicone aquarium tubing to transmit vacuum from the UIM. All it took was 0.5-1.5 seconds of cranking to start the engine no matter what. My mom saw the first startup right before she passed away, and saw it start & run a few more times as well so there's no questioning that it worked in this iteration. Injector Duty Cycle was around 6.7%, so it was running quite rich and stumbling a little when trying to settle down under 1000rpm. I suspected the vacuum lines, so this was why I bought a GM 3-bar sensor and GOOD silicone line.

The following is with only ECU power and ground connected.
So after the 3-bar weirdness, I pulled the ECU out today and hooked it up to the 12v bench power supply and laptop to see what was going on. ECU Manager is showing 26 PSI of boost pressure and ~4.6v on AVI #9. Tried all of the GM Map Sensor calibration profiles and it still stuck at the same voltage, just different pressure readings as logically appropriate. The voltage reading declines at an incredibly slow pace when the ECU is powered up, but 15 minutes of being off makes it perk right back up to 4.75v from 4.40v.

On a whim, I just reconfigured the input for a stock S4T2 sensor and it went to 14 PSI while reading the same voltage . FD Map sensor reads 14.7 psi. Remember, the voltage is slowly dropping and this test read 4.51v. Even the S2000's Map Sensor reads 8.4 PSI under these conditions...

I've read that the AVIs float at 2.5v with nothing connected as they behave in a manner similar to Voltage Dividers (no input=stay at the middle of the range). However, this does not account for the peculiar behavior of the Map Sensor Input.

Just to make sure, I connected a spare length of hose to the ECU's internal sensor and varied the pressure using my lungs. At rest, it shows -0.9 inHg as appropriate for Ohio's elevation. With some lung input, it reacted correctly as intended, pulling down to around -8.0 inHg and up to 1.0 PSI.

Is my PS2K dying?

Cliff Notes:
Engine starts on PS2K's internal Map Sensor fine, shows correct manifold pressure (-0.9 inHG not running, same on bench test)
Wired up NEW GM 3-bar sensor to PS2K (never had Map sensor connected before), Engine floods on startup attempt.
Wiring is Known Good, Relays are Known Good. Power, Ground and Signals are all Known Good.
ECU Manager reports 26 PSI (~4.6v but declining slowly) on bench test with 3-bar sensor, constant -0.9 inHg with internal sensor

 

Did you change the configuration from internal to external sensor? What is the MAP reading when the external sensor is connected and the key is on, engine off?

 

did you try the lung test with the external sensor?

 

Car cranks at ~230rpm (plenty to start with when using internal sensor as I've done before).
3-bar sensor reports 1.2 psi of boost when on but not running, but responds to lung test in both directions, 2.3 psi when blowing and -0.7 inHg on inhale respectively

Internal sensor reports normal -0.9 inHg

3-bar reports boost when it should report vacuum...

 

What sensor calibration are you using?

What is the raw voltage on the input with key on engine off?

You state when you blow into the sensor the reading goes positive but "3 bar reports boost when it should report vacuum". Those two statements don't parse.

 

Sensor Calibration file is GM 3-bar, included with ECU Manager V1.11.1

The raw voltage was in the 1.6-1.7v range IIRC (I didn't log it, forgive me on this one)

According to this chart, courtesy of Injector Rehab, the sensor is reporting normally as it should.
Map Sensor Pressure vs Voltage

To help comprehension, here is the data I have. I did the second test a few minutes ago, while the first test was a few days ago. Again, I apoligize for any fluctuation in data as my lungs aren't the most regulated source of positive/negative pressure and I currently lack a mityvac and compressor.

Haltech Internal Sensor:
Key ON, Not Running: -0.9 inHg
Lung test, Negative pressure: -8.0 inHg
Lung Test, Positive pressure: 1.0 PSI

GM 3-Bar Sensor (First test):
Key ON, Not Running: 1.2 PSI
Lung test, Negative pressure: -0.7 inHg
Lung Test, Positive pressure: 2.3 PSI

GM 3-Bar Sensor (Second test):
Key ON, Not Running: 1.4 PSI (1.80v)
Lung test, Negative pressure: -1.7 inHg (0.76v)
Lung Test, Positive pressure: 2.4 PSI (1.91v)

Also, I doublechecked the Haltech's sensor power output, it is exactly 5.01v measured at the sensor power bus bar. Continuity in all wiring is 0.07 ohms as appropriate as well.

 

im confused.. you first post says the 3-bar map sensor reads 4+ volts, but your last post says its reading fairly normal. or are you measuring the 1.8v from the sensor itself and not through the haltech? you can calibrate out the minor differences in the options page

 

Post a screen shot of your MAP Calibration window.

 

Okay, let me repeat this once more for clarity...

The first post did NOT have the sensor connected. It was only the Haltech with 12v+ and Ground connected so it would boot up and connect to the laptop. The normal 'float' voltage on the AVIs with nothing connected to them is supposed to be approximately 2.5v according to several sources including Haltech unless ranged differently such as the O2 sensor (0-1v range, floats at 0.5v). My AVI9 (External Map Sensor) floats at 4.5-4.75v with nothing connected.

This reading of 4.5-4.75v translates into 25-26 PSI of boost pressure with no sensor connected as indicated in ECU Manager's virtual gauges.

Now, back to the present:

Using a spare pigtail, I hooked up the 3-bar sensor to my bench power supply's 5v terminals and found that at atmospheric pressure, it reads 1.86v on the sensor wire (middle terminal). This is close enough to be consistent with what I saw earlier on the car today (1.80v with Haltech powered up).

In a side-by-side-by-side test,
Haltech internal sensor: 98.9 Kpa
Atmospheric pressure according to Ubuntu Weather: 102.83 KPa
3-Bar sensor Voltage: 1.85v (114.58 KPa)
Correct voltage for ~98.9 KPa on 3-Bar sensor: 1.55v

Diagnosis: Defective 3-Bar Sensor

 

my tuning style is more monkey with screw driver than your mad scientist, i'd just pick a map sensor and start tuning....

 

I had tried to post earlier that it looked like it may be a defective sensor but the post didn't make it from my phone to the board.

My WAG on the 4-ish volts on the input is that there may be an internal switch to the pull-up/down for the internal or external MAP sensor circuits. When internal is selected, you may indeed get what you found. Just a WAG. In the end, everything appears to be working in the ECU.