BMW X5 4.4 2008 – DIAGNOSE CODES P1055 AND P1058

This vehicle came in with customer complaints that the engine goes in limp mode, all lights go on at the dashboard, like abs, brakes, 4×4, engine failure, gearbox failure, etc. I have got some obd2 fault codes from the ECU P1055 and P1058 – these codes have something to do with the vvt motor. I was not happy with these codes so I did some more tests after a while I found that the alternator is not charging, it was charging at a rate of 12.5 volts, which is well below the charging rate of at least 14.00 volts. The battery light at the dashboard did not give any warning that the alternator was not charging. It was on when the ignition key was turned on and after the engine started the light go off, it looks normal, but for such an expensive car, the light does not work properly. In older cars, the battery light will stay on if there is something wrong with the alternator. After testing with a voltmeter I determined that the alternator is not charging. The alternator regulator was faulty. Hope this will help someone else with the same problem.

Updated: 20th Feb 2022 — 9:53 am

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