MAP Sensor Voltage

[Mr_Canoehead]

My 2006 has been acting like the MAP sensor isn't working properly (stumbling and misfiring inconsistently below 3000 rpm and running rich (12.8:1 according to the PCV AT) at idle). I read a post here where someone found some spooj in the hoses that run to the MAP sensor, so I took all those off and cleaned them out with TB cleaner and a pipe cleaner. I also cleaned out the four ports to the intake manifold with some TB cleaner and a paper clip.I did get some crud out of the lines but probably not enough to create a blockage.

Then I did the manual test of the MAP sensor. The Yamaha shop manual says to measure MAP voltage with the ignition on and the engine off and that it should be 3.75-4.25v and to replace the sensor if not in range. Well, mine read 3.42v. So I borrowed the spare I have on a low mileage 2011 intake assy I purchased off ebay and got exactly the same voltage. What are the odds that both are out of spec and showing exactly the same voltage?

I added and removed vacuum from the MAP sensor using a vacuum pump and it reacts normally. I then hooked it back up and fired up the bike and the voltage changes when the engine is rev'd up. It seems to be working properly.

Has anyone else measured their MAP sensor to see what the ambient voltage is? Should I be worried? I am at 3500' ASL so I'm thinking that may make it read a bit low but the manual doesn't make any allowance for altitude.

 

[Fred W]

Sorry, can't help with the nominal voltage question. Just wondering, isn't the MAP sensor a pressure differential sensor? It shouldn't care what ambient pressure is, just how different the manifold pressure is from ambient. That is my limited understanding of it, anyway.

 

[FJRLoonie]

I'm in Calgary with a 2009. If you can provide some guidance on getting to the MAP sensor and where to measure, perhaps I can help.

 

[RossKean]

A failure with the MAP sensor should generate a fault code. (None evident??)

See

https://www.fjrforum.com/forum//index.php/topic/170314-fault-code-14-gen-ii-solved/

Careful with the MAP sensors, they can be easily damaged!!

Before I did anything else, I would remove the Power Commander from the system. Something easy to do, doesn't cost anything and they have been known to be "bad" - reconnect your O2 sensor if it is disconnected).

Next thing might be worth checking is your throttle position sensor. This could be causing the symptoms you are seeing. The TPS may or may not show as "bad" using the bike's diagnostics routine (but I would start there). TPS problems are more evident when the bike is hot and with the vibration during operation - a cool test without engine running might not reveal any issue. Gen II is not renowned for a lot of TPS problems (unlike Gen I and some Gen III).

After that - vacuum leak, plug wire (or bad plug), crapped up injector(s)...

 

[dcarver]

Mine is showing similar symptoms. Acts like it's running lean just off idle up to about 3k rpm.Maybe I'll find some time and mess with it.

 

[Mr_Canoehead]

Thanks for the replies, everyone. There are no codes present. The interesting thing is that it will run fine for a while and then suddenly start running badly after a restart, which is why I thought some gunk might be blocking the signal to the MAP. It seems to run better when the engine is very hot than when it is cold.

I did change the TPS to the one from the 2011 TB assy. That was my first thought based on my research here. No change in behavior.

I bought the 2011 TB Assy off ebay to get the TPS and MAP for less than either part new. It was a deal and only has 11k kms on it, so it looks like a brand new part. I have been thinking about just installing the whole thing to get the newer linkage and clean injectors and then give my 2006 TB a good cleaning over the winter.

I have the PCV and AT set to all zeros from 0-2750 rpm to try and eliminate that from the equation. It runs well over 3000 rpm. I also ran with just the smoothness map with the AT off for a while - no change. I can try disconnecting the PCV next.

Fred, you are probably right on the differential pressure rather than absolute pressure. Still not sure why two of them read low voltage (and exactly the same). I was using a new VOM - maybe I need to check that against an old one.

FJRLoonie, you have to lift the tank and remove the insulation blanket, then probe the sensor. If you are going to be lifting the tank in the near future, I'd be interested in hearing your results.

Other info - I replaced the original ECU with an altitude fix one this spring, it was behaving the same before which I thought was altitude sickness but while the sickness is gone in the mountains, this behavior remains. I have a certain mountain pass that will trigger altitude sickness every time.

Plugs are new last winter (old set did the same) but the coils and leads are original.

I did take it for a spin this morning and it is running well, but one ride is too little to really know. I'll try to get it out again but it's supposed to snow tonight.

 

[Constant Mesh]

Likely just reads absolute pressure, not differential.

Otherwise, why would it have an output above mid-scale when there's no vacuum?

On the pre-2006 models there were two identical pressure sensors. One for the atmosphere, one for the intake pressure.

Obviously both of those read absolute pressure, 0 to 800 mm Hg, or some narrower range.

The 2006 sensor has the same part number as those above so it's likely an absolute sensor too.

The 2006 sensor provides both intake and atmospheric pressures just not at the same time. When the engine isn't running it provides atmospheric pressure. When it's running it provides intake pressure. The atmospheric pressure is stored and updated in the computer whenever a new value is available.

The intake pressure is subtracted from this stored value yielding the vacuum at that moment.

The atmospheric value is updated when the engine is running and the throttle valves are opened enough where the vacuum is much less than the 250 mm Hg value calculated at idle with the throttle valves closed. Don't know the algorithm they use for deriving the atmospheric pressure when the engine is running.

 

[HotRodZilla]

Disconnect that PC-V and see what happens. Hate to say it, but their software is ****, and unreliable. If you have a PC product and have any type of fueling problem, it's probably caused by the PC. Maybe start simple and make sure your grounds are solid. That's a common problem. If the ground is tight, and the connections are good, pull it out. Should be a 5 minute job. May save you a LOT of hassle and unnecessary testing and angst.

Obviously, my bet is a bad PC-V, either connection or internal.

 

[Mr_Canoehead]

I tried disconnecting the PCV yesterday, same issue. I didn't reinstall the stock O2 sensor but I bypassed the PCV at the TB's and fired up the bike. I also double checked the PCV ground.

More info: The bike is stumbling when revved at from idle. It is behaving a lot like bhendron's issue: https://www.fjrforum.com/forum//index.php/topic/171648-2006-gen-ii-runs-rough-between-2k-and-3k-rpmunless-cooling-fans-are-running. It's not a voltage issue, the voltage is good whether the fans are running or not. It is running A/F ratio around 12.0:1 at idle, PCV connected or not.

I looked at the diagnostic screen for the MAP and it says "87". It does decrease when the engine is cranked. The FSM describes this as the difference between ambient and intake pressure - I would expect to see either 0 (as in no difference) or 100 (as percent) but the FSM isn't clear. The FSM also says that if it changes when cranked, it's all good.

I'm not sure what 87 is, the ambient pressure is 101.5 kPa (761mm Hg) here today. Can someone check their diagnostic (Test 03) and tell me what they see? For the hell of it, I plugged the spare MAP in and also got "87" which is at least consistent...If I unplug the sensor, the display goes to 125.

I found a thread where someone was comparing the FJR MAP to a GM MAP sensor and came up with this graph of the behavior of the Yamaha MAP:

So, it appears that 87 would be 87kPa at 3.4v, which is consistent with what I am seeing and also consistent with the manual looking for 3.75-4.25v. However, it is way too low...

 

[HotRodZilla]

What about your TPS? FredW, Ionbeam and a couple othere are very knowledgeable about the testing procedure for that. Since it's not your PC-V, and a few TPS units have gone bad in the last year, it's something to consider. Problems like this suck! Good luck.

Oh, and if your MAP sensor is bad, I would expect to see different readings with the spare one installed. Weird...

 

[RossKean]

I can't check mine right now - maybe tomorrow after work if nobody else gets back to you in the interim. As I mentioned, it is quite possible to damage the sensor. If you used a pipe cleaner inside the sensor, you could have punctured the diaphragm. Also, I don't know what the designed vacuum range is for the sensor - applying high vacuum with a hand pump might have ruptured it as well.

As per my earlier post, you may want to rule out the TPS. Looks like you verified the Power Commander. Have another look for vacuum leaks too.

 

[Mr_Canoehead]

A couple of other things - I plugged -15% into the 1000 and 1250rpm @ 0% throttle boxes on my PCV map and that brought the idle mixture to 13.2:1. For the hell of it, I took the bike for a spin at this setting and it ran great.

I didn't think to check the input voltage to the sensor while I had the tank up. I assume it should be 5v?

Thanks, 'Zilla, I did change out the TPS with the spare one from the 2011 for the hell of it (and set it to the right voltage) and it didn't make any difference.Since it was a PITA to change with the location of the screws, it is currently running with the 2011 unit.

 

[Fred W]

OK, there is good reason for confusion regarding the intake pressure sensor. On 1st Gens there were two pressure sensors. One for intake pressure (vacuum) and one for atmospheric pressure.

With the ECU changes in 2006, 2nd Gens lost the atmospheric pressure sensor altogether, so it now has to record and store the ambient atmospheric pressure. I guess in retrospect that explains why the 2nd Gens suddenly began to experience the "high altitude sickness" problem which was fixed in firmware via an ECU recall.

The remaining intake pressure sensor is still a differential pressure sensor, but it is comparing the actual pressure in the intake manifold to a sealed chamber inside the device.

To compound the confusion, in the factory service manual, diagnostic test #03 is called "Pressure difference (atmospheric pressure and intake air pressure), says the meter "Displays the intake air pressure", and the test says to:

"Set the engine stop switch to “run”, and then push the start switch. (If the display value changes, the performance is OK.)

So the initial display number is the ambient atmospheric pressure, and the display with the engine turning over is with manifold vacuum. As long as there is a difference it says the test passes.

Nowhere that I can find does it say what the units represent that are being displayed. I suspect that they are just the A2D digitized voltage from the sensor and not "calibrated to" or indicative of any particular vacuum / pressure levels. I also do not see where it says the allowable range of the digital display.

The sensor voltage test does say the range is 3.75 - 4.25VDC between the pink/white (ECU signal) and black/blue (ECU common) wires. It would be important to use the ECU common and not chassis ground as the reference. Either way I wouldn't get too upset what the absolute voltage or digital value is as it would be the difference between the recorded ambient pressure and the vacuum when the engine is running that would be important to the fuel injection duration control.

 

[Mr_Canoehead]

Fred, based on what I am seeing, I think the dash actually displays pressure in kPa. The big issue is that both of my sensors fail the 3.75-4.25 test, both showing 3.42v (across pink and black wires). This corresponds to 87kPa in the chart I posted above, which is also what both sensors display on the dash. If one sensor showed 3.41 and the other showed 3.75-4.25, I'd be done. But in this case, they both show the same (out of spec) value.

Ross, I didn't take the pipe cleaner to the sensor, only to the tubing and joints. I also applied vacuum by sucking on the tubing, I resisted using my brake bleeder vacuum pump. Both sensors appear to be working correctly, passing the diagnostic test, but failing the device test. The diagnostic test only tests that the value changes when the engine is cranked but gives no guidance as to what resting pressure should be.

I think my next step is to measure the voltage to the sensor and see if it is 5v but I am open to any suggestions....

 

[Fred W]

Yes, it appears that you are right. I cracked open my 3rd Gen manual to find the following:

"Execute the diagnostic mode. (Code No. 03) When engine is stopped: Atmospheric pressure at the current altitude and weather conditions is indicated.
At sea level: Approx. 101 kPa (757.6 mmHg, 29.8 inHg)

1000 m (3300 ft) above sea level: Approx. 90 kPa (675.1 mmHg, 26.6 inHg)

2000 m (6700 ft) above sea level: Approx. 80 kPa (600.0 mmHg, 23.6 inHg)

3000 m (9800 ft) above sea level: Approx. 70 kPa (525.0 mmHg, 20.7 inHg)

When engine is cranking: Make sure that the indication value changes.

The value does not change when engine is cranking. → Check the intake air pressure sensor. Replace if defective. Refer to “CHECKING THE INTAKE AIR PRESSURE SENSOR” on page 8-177."

I imagine the 2nd Gen should be the same. I just checked mine and I got 102 static, dropping significantly when I thumbed the starter. Local weather web site says my local pressure is 102.9 today (I don't have a barometer).

 

[Mr_Canoehead]

Thanks, Fred. The lightbulb just went on - I may be OK - I was wondering why I get 87 kPa (at 3500' ASL) but I googled it and apparently airports correct their readings to sea level, which is why my local airport shows 101.5 kPa. (Actually, I was wondering how my local airport could be 101.5 kPa).

Doing the calculation the other way, 101.5 kPa at Sea Level would be 89 kPa at my Altitude and temp. Close enough to 87 kPa. I'll see if I can get confirmation from someone else in my area as to what they get.

 

[Fred W]

Thanks to you, too. I learned a lot about these sensors through this thread. I'd never really looked into them that closely. It's pretty cool that the diag display tells us the barometric pressure (in kPa) when the bike isn't running.

 

[Constant Mesh]

The 800 mm Hg range I mentioned is derived from a Gen 1 service manual.

It shows if either of the pressure sensors malfunction the computer automatically uses 760 mm Hg (sea level pressure) in calculating injector fuel output. We know that the sensors are identical and the '06 FJR uses the same sensor too.

If these sensors malfunction the engine can start and you can ride in this condition. The computer just uses the value above in lieu of actual data from the sensors.

On the Gen 1 Diagnostic Code 02 displays the atmospheric pressure. Doesn't show the units. Diagnostic Code 03 displays the pressure difference (atmospheric minus intake pressure). 10 to 200 mm Hg is displayed.

All pressure sensors are differential in principle. You have a diaphragm or some interface where different pressures are applied to opposite sides of the diaphragm.

The sensors in use here have a sealed vacuum applied to one side and the atmosphere or intake applied to the other side. By definition this is an absolute pressure sensor. It has a high vacuum sealed behind the sensing diaphragm. The vacuum is negligible relative to the pressure being measured.

So the measured values are always referenced to a high vacuum internally contained in the sensor.

 

[Mr_Canoehead]

I guess Yamaha went to one sensor to save money, since they want so much for a replacement! Thanks to everyone for the help and I'm glad I didn't buy yet another sensor when they failed the bench test.

I would be really interested in the algorithm that allows Yamaha to update the atmospheric pressure while the engine is running using only one sensor for both functions. I can see why they got it wrong on the 2006/2007 bikes, it can't be an easy calculation. I assumed that there was a sensor built into the ECU.

I guess the wording in my manual about pressure differential was carried over from the Gen 1 manual since the Gen II diag screen doesn't show differential pressure.

So, the good news is my sensors are OK. The bad news is I'm back to square one on why it is running poorly and so rich at idle. I think I am going to do the Barbarian mod, just to see if the CO level is set crazy rich.