P0601 Internal Control Module Memory Check Sum Error???

[Mike WW]

Title says it mostly, but I'll add a little background. Wife got on the freeway in the 00 528it today and all of the sudden it nearly died. No power, but some surging. Pulled over put it in neutral and the same. Finally turned it off and called a tow truck.

EML light was on. Got it home, it did start, but ran very poorly. It sounded like a vacuum leak from towards the front of the intake manifold area, but under. It's running, not too bad, but not happy. I'm kind of pulling on this and that to see if I can find anything, pulled lead off the AMM and it hickuped then ran about the same, maybe a touch better, maybe not. Plugged it back in and it did the same. I'm leaning and listening to things and all of the sudden it cleared up. Hissing noise nearly completely went away, ran nice and smooth, rev'd quick and clean up high. So I scanned it and came up with P0601, P0443 which is Evaporative Emission System Purge Control Valve Circuit and has been coming and going for a while, and a pending P0304 which is cylinder 4 misfire.

Car had been running perfectly since I did the Vanos rebuild a year ago, no hickups, nothing odd, 20K miles and getting 25-26MPG. Any thoughts?

[BrandonWA]

I did a little research for you. I would reccomend taking your car to your local indy and getting a real diagnosis. It seems that your Engine Control Module has failed, providing you with the check some error. The ECM controls the Evaporative Emissions System (EVAP) by operating the ground circuit and allows gas fumes to enter the engine. When the solenoid in the EVAP system is activated, the ECM should see the ground voltage pulled low, close to zero. If the ECM doesn't see these expected voltages, or senses an open in the circuit, this code is set. My guess would be that your driver circuit inside the powertrain control module (PCM) is bad.
Here are some links on information that you should read up on:

http://www.aa1car.com/library/pcm.htm
http://www.obd-codes.com/p0443

Also, is your car chipped?

[Mike WW]

Thanks for the reply. The car is stock, not chipped. My first thought was ECU, anything logic related points me in that direction, but on further reflection I'm thinking the electronic throttle body. It fits all the symptoms.

1. Hissing noise
2. Running badly
3. EML light
4. When it cleared up, the hissing went away
5. One thing I forgot to mention, I had a lack of brake assist when I pulled it into the driveway after the wife got towed home.

With all that I've got my fingers crossed that it's a sticky throttle body, the checksum error was because of a feedback circuit between the closed acc pedal and the WOT throttle body. That diagnosis would fit all of the above, now I've just got to hope I'm right, LOL. It'll be out for cleaning on Friday.

[Mike WW]

Just an update. After cleaning and polishing the TB (which wasn't really dirty at all), replacing all 4 hoses attached in any way to the CCV and eliminating what may or may not have been a very slight preload in the throttle, I have had no further problems in roughly 50K. I think it went into the failsafe/barely running mode 3 times all after full throttle application. At least a couple of them also sent the tranny into limp home mode, but nothing like it in almost 2 years now.

[rf900rkw]

Check battery, check connections, check alternator, clear code. The usual cause of this code is a low/high voltage spike during the power-on selftest. If the codes come back and everything electrical is up to snuff, you'll have to dig farther.