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Old 02-09-2011, 04:31 AM
Join Date: Dec 2010
Location: UK
Posts: 10
haydar is on a distinguished road
That is a good point and I did read about these issues. So the first thing we did was put in a new ignition switch and gear selector switch.

One thing we found was that when the problem occurs, the diagnostic system says the issue is current. However if we delete the error codes then the problem goes away, only to come back the next day. Today we disengaged the battery and once we connected it back the problem came back. So disconnecting and connecting the battery causes the problem to come on too.

This has got us all scratching our heads!
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Old 02-09-2011, 08:18 AM
Join Date: Jan 2009
Location: UK
Posts: 2
Bemble is on a distinguished road
It sounds like the ‘Pressure Control Solenoid 2’ error is a red herring then.

On the Range Rovers a common cause of the ‘TRANS FAILSAFE PROG’ message is the transfer box motor potentiometer which can lose its signal (the transfer box ECU & transmission ECU are connected via the CAN bus).

I realise that the E53 has a single speed transfer box (NV125) and not a two speed (NV225) unit but the reason I mention it is that the DTC is not correctly identified using the Autologic diagnostic system which the ‘Independents’ use yet the ‘official’ Land Rover Testbook/T4 system does identify the fault correctly.

Presumably there’s a BMW equivalent of Testbook and I wondered if it might be worth running a diagnostic check on that rather than Autologic to see if any different DTCs are flagged?

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Old 02-09-2011, 10:22 AM
Join Date: Dec 2010
Location: UK
Posts: 10
haydar is on a distinguished road
On a hunch we swapped the control units and guess what, the problem went away! Now are control units coded items or if I buy one from Ebay or something, will it work?
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Old 02-09-2011, 06:19 PM
amacman's Avatar
Join Date: May 2008
Location: glasgow,scotland
Posts: 1,462
amacman is on a distinguished road
any control unit from the same model and production year will have the same coding as your existing unit .
units from different year or model will require coding to your vehicle .
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Old 03-18-2011, 02:06 PM
Join Date: Jun 2007
Location: Louisiana
Posts: 12
daneshfar is on a distinguished road
These forums have helped me so much i need to give back. After I fixed my window mechanism, testing it up and down, the next morning car would not crank over but all kinds of things flickered and clicked. I set battery charger and left for the day. Of history I had alternator changed 2 years ago (but this is same battery that at the time had to be charged several times and was probably stressed when BMW figured out my car was just shy of making enough juice with bad voltage regulator..they changed whole thing for 900). back to now; After I got home I tested battery from engine bay and measured 16.5 volts and when engine on running 17.5 volts. Couldn't figure out how you can get such voltages and took off connector to MAF and alternator to blow clean and reconnected (So i thought). Did some research online and you can not get these voltages out of a 12 volt system, I HAD LOW battery in my Multimeter, replaced and got 12.8 volts off and 14.2 volts with car running. These are what it should be and I thought great all is fixed and battery was just low and now that its charged all is good. NExt morning starts great and engine runs fine drove one block and got TRAN FAILSAFE PROG. Shifting almost normal but rougher than should be specially when slowing down from 20 to 0 it downshifted rough to 2 and 1 st gear to stop. I am panicking over my transmission now!!!. Took car home went to work. Came home and tested battery down to 10.7 volts (my meter is good now with new batteries in it). I take battery completely out of car thinking must have a draw on it. Charged all night and next morning got 11.4 volts and within 30 minutes get 10.5 volts. Battery must be bad. took to walmart and battery tester says bad cell in battery . Got the 3 year free replacement EVERLAST 82 dollars and size 94R and brought back fit perfectly. Started car no problems. Drove off and instantly TRAN Failsafe PROG. I am panicking calling BMW for appointment and they are of no use on the phone just want you to bring in and check. Took to Autozone and reads out a MAF issue. ENGine now starts and runs normally so I think that is not right. Had appointment for 2 days from now with BMW decide I will check under hood and look at MAF(mass air flow) and SEE ITS NOT PLUGGED IN!!! I did that?
Plugged in and drove off, TRAN FAILSAFE PROG GONE!!! but still SES (service engine soon light still on. After 3 or 4 turn on and off going places it is now OFF too!!!
So here is the analysis, LOW battery and bad cell was culprit all along, My own fault to dissconnect MAF harness and not reconnect. So if this is not connected this TRAN failsafe prog warning will be seen!!! what the hell these two have to do with each other I don't know. ALSO WHY WOULD AN ENGINE RUN BEAUTIFULLY if the MAF is bad or in this case NOT even plugged in.
NOW battery measures 12.9 with car off and 14.1 volts running. This tells me regulator and alternator working. All my warnings are off. Cancelled BMW appointment. Got cheap battery with 3 year warranty free replacement.
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Old 04-04-2011, 08:22 PM
xmac's Avatar
Join Date: Jan 2006
Location: California
Posts: 15
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The reason the car still runs with the MAF disconnected, is that the ECU uses some default calculations for airflow. It looks like the engineers envisioned one day the MAF would fail and they did not want the engine to simply shut off. I fought a problem for several months and it turned out to be a bad MAF - event though no codes were recorded.

Back to the tranny. Thanks for the info, I am now having the TRANS Failsafe error on my 2001 4.1 with no error codes and no crazy downshifting. The error clears upon restarting the engine. Around the same time of the first error, the rear wiper stopped working and the radio randomly turning itself off. Not sure if they are all related or the grim reaper is showing up soon.

I replaced the battery a few months ago with the Autozone version (bad cell at the time with the OEM battery) and am wondering if that is the culprit.
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