tjkarch60

UPDATE: After taking the car for a test drive the same symptoms returned, although not as bad. When the engine was cool it drove like new, smooth and perfect. Again, with enough throttle to maintain speed there were no problems. But after giving a little throttle it would drop rpms and stutter with no loss of power or cutout of electrical (like the radio cutting out.) Full throttle is normal with no stuttering.
I'm not sure what it could be. I'll look at the spark plugs, but they aren't that old and I think they would cause problems at all throttle positions. I don't think it could be fuel filter because again that would cause problems at all throttle positions. The dealer checked the alternator and regulator and they passed. The also passed when Autozone checked it the their tool.
There are no codes being given, including the 2B71 code originally given. I asked about the O2 sensors at the dealer and they said they were good (at least no codes being given).

Any ideas? It starts and idles fine and the before I fixed the DISA I would also get a code for the Dynamic Drive in INPA and on iDrive. I'd pull over and turn the engine off and restart it and the iDrive warning would disappear. The INPA code was for a voltage spike, but it hasn't returned since fixing the DISA. It wouldn't seem like the 2 problems are connected, but they are both gone now.


I have a 2005 545i and was experiencing a RPM drop of 100-500 rpms while using a light to moderate throttle. The car started and idled perfectly and full throttle was strong and normal.

Using INPA I had a 2B71 error code, which is the DISA mechanism. Since a DISA motor is $500 on Pelican Parts, I wanted to be sure it was not just a sensor or module or something else minor and took the car to a BMW dealer and ponied up the $145 to verify the problem. I figured they had the ability to narrow it down and to see if there was something I missed.

As it turn out they said it was the DISA motor and it would be $1200 to replace. Because I researched how to work on the DISA, I decided to try and do it myself.
After I removed the DISA motor, I looked at it and it seemed fine. I pulled the plastic electrical connector/gear drive cover from the motor itself. I tested the motor with 12VDC and it worked perfectly fine. There are 3 sets of very small wires that run from the circuit board to the connector and at least one set of wires had come unsoldered. I resoldered all the wires, but it back together and the car ran normal and there was NO error code in INPA! Those little wires were the problem.

As it turns out, removing the DISA is not that difficult IF you:
1. Take your time and don’t rush!
2. Use the right sized tools to fit in the tight spaces.
I used a ¼ inch drive ratchet on the top bolt because it is the tightest fit and a 3/8 inch drive ratchet doesn’t fit. The 3 screws are a Torx30. I used the smallest 3/8 in drive ratchet I had on the other 2 bolts and tied string to the wrench in case I dropped the wrench into the black hole behind the engine. Then you remove the bolts, use a magnet to hold the T30 bit and the bolt so they don’t fall into the same black hole.
3. Remove the cross bar over the top of the engine, there are 4 T45 bolts. This bar runs from the top of the shock towers to the back bulkhead. Remove the battery cable from the harness clamp on the crossbar.
4. The list of connectors to disconnect is like 12 items. You only need to disconnect the Valvetronics and injector connectors on each side and two other connectors on the front of the wire runs along each side of the intake manifold. All you need to do is move the wiring harness forward so you can reach the DISA.
5. There is a water hose that runs below the DISA and there are clips on the left and right sides. (If you see it, you’ll know exactly what I’m talking about.) I pulled the passenger side hose clip because it was the easiest to reach. The hose is a heater hose and not under pressure and only a few drops of water came out. Take the hose and move it out the way. There are 2 clamps that hold this hose in place to the bulkhead. Remove those, but don’t be surprised if the plastic parts that the clamps screw into fall apart like mine did. I just pushed the clamp posts into the remaining holes and I think it will be OK. There isn’t a lot of room for them to move and nowhere for them to go.
6. I thought putting the bolts back in would be impossible because of the tight space, but it was easy to put them in by hand. Use a mirror to double check the gap on the gear drive matches up with the matching index on the drive inside the intake manifold.
7. When reassembling the wiring connectors, use some dielectric grease if you have it to make future work easier.
8. Take your time and don’t rush!

I should have taken pictures, but wasn't thinking about writing this.