OBD codes and their meanings

[gliff]

BMW330i 2001 M54 Engine

Not sure if this is the right forum so please feel free to move.

After being stung by a bad diagnosis (stealership) once, I have invested in some diagnostics software (CarSoft). Whilst being a very useful tool it has thrown up a few errors that I need peoples advice on. I have managed to use them to get some more details by searching the web and come up with the following.

Can anyone advise?

49 Shift gear stepper
SAE Code NONE
BMW-Specific Code 49
Description DME Internal Test Failed

53 Power supply: solenoid valves/Speed monitoring
SAE Code P1509
BMW-Specific Code 53
Description Idle Control Valve Opening Coil Electrical Fault
P1509 Idle Speed Control Valve Opening Solenoid Control Circuit Electrical

59 Stall speed monitoring
SAE Code P0330
BMW-Specific Code 59
Description Knock Sensor 2 Circuit Electrical Fault
P0330 Knock Sensor 2 Circuit Malfunction (Bank 2)

I am not adverse to paying for work that is needed, however having once paid £500 for a new OBC when the fault was actually with a torque converter I hope you can understand my caution before I go to a garage.

Thanks in advance