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Old 03-19-2017, 09:40 AM
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I have a BMW 630i convertible with SMG transmission from october 2005 with 183.000 km on the clock, and in which the transmission went into safe mode (only available gears 1, 2, 3 and R, and the display showed a cogwheel). My BMW repair shop, an independent repair shop, and a transmission specialist had conflicting opinions about what needed to be done. BMW suggested replacing the entire transmission, because no smaller field replacable part was available. The independent repair shop and the transmission specialist suggested replacing the clutch, because their Bosch testers interpreted the clutch to be the problem. I bought a C110+ tester on the web for 100 Euros, which showed that the fault code was 4f6f: Hydraulic pump activation. The tester would also reset the safe mode and while driving show the pressure in bars in the hydraulic circuit, which alternated between the low and the high forties and dropped sharply whenever the gear changed. Just before going into safe mode, the pressure would drop to 36 bar. I ordered one (1) liter of HIGH performance hydraulic oil BMW SMG 2 from Burkhart Engineering, 29 Euros plus 14 Euros for shipment to Denmark, and had another BMW repair shop change the hydraulic oil in the SMG (not the gear oil, the hydraulic oil), which took them two hours. Problem solved. The old hydraulic oil was black, smelled bad, and there was way too little of it. The car took about 0,4 liters of the new hydraulic oil.


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Old 03-20-2017, 01:36 AM
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The fault also indicated that the hydraulic pump failed to activate maybe indicating a sticky salmon relay or blown fuse. But I have also seen the wires fray right where they enter the pump housing causing a short. Just incase you run into future issues

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Old 03-20-2017, 04:13 PM
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Notice how the C110+ is used to diagnose that the 4f6f fault is due to way too little hydraulic oil, and not due to salmon relay, emotor, transmission or clutch, the replacement of which wouldn't have helped. The significant diagnostic method to understand here, is the interpretation of the graph output from the C110+.

Notice also that conclusive feedback about the validity of the diagnose is directly available in the form of the quantity of oil drained from the SMG.

Notice also the erroneus conclusion drawn by the two repair shops, who did not analyze graphs but tried to reach a conclusion from the 4f6f alone.

The high performance hydraulic oil, although the procedure would have worked with CHF 11S too, is also a good tip, I think.

Last edited by mosfeldt; 03-21-2017 at 08:00 AM.
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