Confused with P1105 Code - Manifold Differential Pressure Sensor

[Seven Zs]

Hi -


First post, but have been searching deep in the forums for a while now as I go through my new to me 2007 Z4 3.0i with 75k miles.


I continue to get a P1105 code, which isn't heavily discussed on this forum or others. From what I read and from the local indy's suggestion, its the Manifold Differential Pressure Sensor. Short story is, I've replaced it (twice) and still getting the code. No other codes. Here's what I know:


No real symptoms, car runs and drives great - idle wasn't smooth when I got it, but with what I've done it's smooth now. I've done the plastic valve cover (which includes PCV on this engine, no separate CCV), plugs/coils, intake manifold clean and gaskets, throttle body clean and gasket, new breather hose, new air filter, etc.


When I had the old plugs out, they all looked evenly worn and not sooty. Intake valves looked shiny when I had the intake manifold off.


I find that after I clear the code, drive the car, then turn the car off and restart it, that's when the code appears.


Only other potential oddity I noticed was when I remove the oil filler cap, there's some vapor that cycles in the valve cover when running and some escapes when the vehicle is off and I remove the cap. No air comes out, just very slight vacuum. I've owned many many cars, and never recall removing the cap while running so I'm not sure if that's any indicator. I did however smell the vapor and the inside of the valve cover and the oil has an exhaust smell to it...fresh oil change too.


I'm stuck...


Thanks for any input.

[Clearancediver]

I think your best course of action would be to go to bmwtis.com and pay for access and see what technical advice/direction is given to BMW technicians for this error code.


Sent from my iPhone using Tapatalk

[dbarton62]

Apologies if this seems obvious.
A search on REALOEM for part # 13628657300 Pressure Differential Sensor.

https://www.ecstuning.com/b-genuine-...628657300~oeb/

Returns this result.

https://www.realoem.com/bmw/enUS/sho...56#13628657300

Not one to throw parts at a car to chase codes but the code is pointing directly to this sensor. Its easy to access and relatively cheap. May be worth a try.

[Seven Zs]

dbarton62, thank you. Copying my other reply below for record in the vent others are ever curious. Clearncediver - I tried that site and its not loading, I'll try from another device, thank you.

I did replace that part as the first response to the code reappearing, and still getting it. I took it to the local indy euro shop today and they suspect that it's an unmetered air leak. They smoke tested it and said the intake boots are misshaped and not sealing well from years of tightening/loosening. We'll replace those and see if that does the trick, otherwise they'll continue to diagnose other systems. They did also notice a previous owner installed a Dinan throttle body (I'm still learning this car and realized that's an "upgrade" to OEM) and will be calling their Dinan rep to see if they need to check ECU settings.

[Seven Zs]

Think this one is solved. Replaced the Dinan TB with an OE one and sanded the plastic mating surface smooth on the intake manifold. Torqued to 9 nm.

So far, no trouble codes or pending codes. Before, it would show a pending code P1105/2d29 immediately after startup and light the SES light on the next startup. Hope this one is done.

[BimmerBreaker]

It is important to note that when an error code indicates something like "Mass airflow sensor" or "Manifold Differential Pressure Sensor" that it does NOT mean those sensors are faulty; rather it is registering an issue related to the signal of those sensors. Diagnostically you can use this information to help narrow down where the problem is but those types of error codes do not mean a bad sensor

In this case what it seemed like happened is a different size TB was installed (a pointless mod anyways due to Valvetronic) which affected the air pressure inside the manifold, putting it outside of expected values, triggering a CEL. Its the same as when you develop a vacuum leak and get a code for a MAF. The MAF isnt faulty, the DME is just realizing there is more air in the engine due to the vacuum leak than the MAF is accounting for. This is the same type of situation

If it said Manifold Differential Pressure Sensor "No Value", "Short", "Out of expected range" or sometimes just "fault" then yes by all means consider replacing the sensor. In those cases the DME detects a 0v or 12v value when it should be 5v or a wave signal and it knows the sensor is faulty

[Seven Zs]

Great insights, BimmerBreaker, thank you. Your logic makes perfect sense. I did finally check voltage and resistance and the sensor and harness were working as they should. What tipped me to do the TB next was another post where someone was experiencing the same issue with an aftermarket intake. Reinstalling their OE intake made it go away and never return. Other than that, very little info on this code when it’s not also paired with another, but now I have another wrinkle in the brain and can enjoy it! Btw, you’re spot on - I noticed no difference in performance putting the OE TB on in place of the Dinan. Thanks again.