MAP Signal going out is just slightly lower, but still in the 5V range. With a 5.023V reference signal, the MAP Signal voltage going to PCM is 5.006V.

Brand new replacement MAP sensor shows the same reading.

These readings are being taken by having a jumper connecting the 5V ref signal terminal from the harness to the reference signal input terminal on the MAP sensor. I meter the MAP signal output terminal. I've done low-voltage electrical work my entire life, so I'm solid with electrical testing.

 

Ok, sounds like your sensor isn't reading any pressure.

Let me get home and I'll try to explain better....

 

Yeah, I know. But a brand new sensor does the same...very odd. I did just swap the sensors when the new one arrived. If there is an intermittent short in the wiring, and the 5V ref signal was sent to the MAP signal output terminal, perhaps that could have toasted the new MAP sensor. But I'm not sure what the sensor consists of, so no way to know that for sure. All of my testing this morning was done without the manifold air line connected, so there was no influence from a plugged line, etc. It should have been outputting a voltage equivalent to 12.3psi (whatever that voltage would be).

 

Sorry bud, your testing technique is good on a DC analog sensor. Excerpt from the PC/ED:

Digital Manifold Absolute Pressure Sensor

The digital Manifold Absolute Pressure (MAP) sensor is a variable capacitor sensor that is supplied a 5-volt reference signal by the PCM and returns a digital frequency signal to the PCM relative to intake manifold pressure. The sensor frequency increases as pressure increases. The MAP sensor allows the PCM to determine engine load to calculate fuel quantity. In addition, the MAP signal is used to control smoke by limiting fuel quantity during acceleration until a specified boost pressure is obtained. A MAP signal fault detected by the PCM will cause the PCM to calculate an estimated manifold pressure based on known engine conditions.

Got O-scope?

 

Well, hell. If it's a frequency-based reading, that would explain the voltage being close to the same, with a slight drop. And the $160 price tag for the sensor. But what threw me is the PDF schematic you posted doesn't show the MAP signal as a dashed line, which would indicate a frequency function...

And no, no o-scope in my possession. Damn.

 

How does that explain both MAP units behaving the same? To me, that points to the pcm not properly recognizing the signal. Have you tried a different pcm?

 

---OR---

AE is converting it incorrectly as 10.7psi, when really it's 12.3psi.

It very well could be the PCM. I don't have a different PCM readily available.

 

I'll look into it some more this evening.

 

Super Duty trucks use an analog MAP sensor. OBS trucks use a digital MAP sensor.

 

What version of AE? As I mentioned in a pm, I might be coming that way. I could certainly throw my laptop and AE (10.3.2) connector in. Stop by get some data, have a barley pop.

 

Testing MAP

 

Now we're talking! I'm on AE 12.0.0. So yeah, bring that laptop. My house is 1 block from Bozeman Brewing, and 3 blocks from Montana Ale Works. Location, location, locations...

 

Ok. I took some pics of some sensor readings. I have two different versions of AE on two different laptops monitoring two different trucks. I'll post up the pics but I found some interesting data readings that I do not know what they mean. It seams AE will drop the MAP 2 PSI on some of my older tow tunes......

So is Steve's MAP reading tune related?

Edit: Steve, I PM'd you my cell # - I'll be in the garage until 10 pm

 

Rich...AE's not dropping the MAP...the tuner is dropping the MAP. In Steve's case, unless he has something flashed to the pcm, it's either AE not reporting correctly or something really unusual is happening with his pcm or wiring.

 

First... I wonder if there are any issues with the MAP from applying a DC signal to a digital input.

Dan V - wasn't it you that said you were cruising through my neighborhood in the future? By the way... great job stepping up!

Tunes and MAP readings: Yes, tuners mask the true MAP reading sometimes, and other times they just cap it from exceeding a reading of 22 PSI. This keeps the SES light monster at bay.

It's my understanding that Steve's MAP reads low without the chip. If this is a case of reading the MAP through the zero position on the Hydra, I say pull the chip altogether for the sake of reading the sensors one time. If it has no effect, put it back on and move on to what's next.

I was fighting an issue with Stinky 6 weeks back (I know when it was because Stinky has been down since then... and I want my truck back). I put the Hydra in "0" at sea level, and I was getting a 12 or 13 on the MAP. Change the tune and I get the normal MAP reading. I wonder if we're stumbling onto a flaw in the Hydra.