Replaced MAF sensor still getting P0172 & P0175 codes

[Harley Monster]

I thought I had this X5 fixed. (2001 X5 3.0)

After getting the SES light and codes P0172 & P0175 I bit the bullet and replaced the MAF sensor.

Before I replaced the MAF sensor I was getting the SES light and codes after about 5 starts and 30 miles. After I replaced the MAF sensor I drove for nearly a month, several 100 miles and dozens of starts before the SES light came on. I was sure I had this fixed.

What are the next logical failures? Many say the fuel pressure regulator or vacuum line to it. How do you go about testing the fuel pressure regulator?

Some list the MAP sensor, can this be checked without a dealer type scanner? Same for the Coolant Temp sensor or Air temp sensor?

The car appears to be running perfect, no abnormalities when driving.

Can you help?

[Harley Monster]

I just ordered a Fuel Pressure Testing kit from Amazon for $30, same kit at the auto parts house was $44.29, $56.99 retail.

I don't think there is any rush because the car seems to be running fine though I understand running too rich for too long can damage the cats.

I have the Bentley book so when I get the testing kit I will go through the fuel pressure test. I think this is the next logical diagnostic step.

There have been a lot of P0172 & P0175 reports on this forum, but very few have posted what the final resolution of the problem was.

If you have had this problem, what fixed your X5?

[Harley Monster]

Question for the trained tech guys on this forum:

I used a generic code reader to get the P0172 & P0175 codes, would a Peake scan tool give me more information to work with or are these codes all I would get even with the Peake?

I am debating about ordering a Peake. My X5 has nearly 120,000 on it and I am sure I will have to be doing more troubleshooting as I have not intention of trading the X5.

Your help would be greatly appreciated.

[Harley Monster]

I have found the problem causing the SES light and codes P0172 and P0175!

I did a more thorough visual inspection and found the corrogated section of the Y on the "Tube Elbow - Throttle Housing to Air Boot" was severely cracked on the bottom side which is not visible from the top of the engine. I found it with a flashlight and mirror. Once I found it then got under the car it was plainly visible.

The part number is 13541440102M9, I ordered it from Pelican Parts for $19.50.

There never was any sound associated with this leak, at least not what my ears could hear. That may because the rips were so large.

I am impressed that the injection system was able to compensate as well as it did because the engine seemed to run fine.

I had replaced the Mass Air Flow Sensor and thought I had it fixed because the car did not throw codes or SES light for nearly a month. I suspect the Mass Air Flow sensor was not up to par and I had a compound problem.

I am pretty sure replacing this intake tube will fix the problem because I taped the splits off with electrical tape then put a couple tie wraps around it so the tape would not come undone. We drove the car all day yesterday, multiple stops and over 100 miles and the SES light remained off.

I get the part tomorrow FedEx ground, I am just hoping I can get to the clamps, they don't seem too accessible. If anyone has any experience changing this duct that could make this job easier, please let me know.

Here is a photo of the bottom of the "Tube Elbow."

[stamas]

I had the same codes and was told it was probably the Mass Airflow Sensor (which is quite expensive).

These codes showed up not long after I replaced my pcv valve... and it turned out they were caused by me... rookie error...

Somehow a gasket ring (rubber ring) had gone missing when reassembling.

This gasket ring seals the connection between the mass air flow sensor and the rubber boot connected it to the throttle housing.

I had tightened down the connection and all seemed well, but there was enough of an air leak that the mass airflow sensor was delivering readings indicating too little airflow... leading apparently to the p0172 and p0175 conditions.

My quick fix... two wide rubber bands... one overlapping the other acting as a jury rig gasket. This will have to do until I locate a proper replacement (part number: 13711440173 for my 2001 X5 3.0i).

[Skyline]

I'm not sure the capabilities of your scanner, but most can show a readiness state. Many faults require the vehicle to go through a drive cycle after the code is cleared to be 'ready'. After completing the drive cycle, the car's computer will either show 'ready', or turn on the SES light again.

On my Innova scanner, it has three lights just below the screen; red (current fault), yellow,(waiting to complete drive cycle), and green. In many states, you can not pass emissions inspections until the car is ready.

Also, there are techniques for accelerating the drive cycle.

[stamas]

Before I posted this successful result (no more P0172 and P0175 errors) I made sure that it was a valid fix.

I do not not use my own scanner... I go to a local auto shop and use their scanner... I do not get the BMW codes but do get the OBD P-codes and have the Bentley service manual to interpret them.

After my fix (replacing the missing gasket on the throttle valve side of the mass air flow sensor) I had the error codes cleared, then drove around sufficiently that if the problem remained, the codes would have reappeared.

So... no more engine light after sufficient driving... I call that fixed. Interesting that a missing gasket and resulting reduced air flow past the mass air flow sensor can result in the P0172 and P0175 errors.