Case Study - E38
728i fails to shift into 4th and 5th gears
|Date of manufacture||Jan 1998|
|Engine||Single Vanos M52|
This was a rather strange one. The autobox operated really well in manual mode, all the gears could be selected with no problems at all. The only problem was that the autobox would refuse to shift out of 3rd gear for no apparent reason. This was an intermittent fault, sometimes the autobox worked perfectly, other times the only way to select 4th and 5th was to go into manual mode and select them manually.
Carsoft showed no autobox faults, as far as the transmission was concerned, everything was lovely. Carsoft did show a fault with the camshaft sensor but this was a common fault that often was often shown erroneously. The engine was running perfectly so this was taken no further.
This problem spanned many months, meanwhile the camshaft sensor was changed as the camshaft sensor fault kept re-appearing. Against all common sense, the replacement of the camshaft sensor cured the problem! I have heard of this happening on one other occasion and am sure the two faults are related to a 'limp home' type ECU mode. This does not seem to happen on any engine other than the 728i.