[soulcrusher]

Hi I'm new to using Ista. I'm trying to diagnose the reason why my car wont start.

A0B4- CAS: Engine start, starter operation.
Terminal 50 to CAS

Last night, the car attempted to turn over, then on the second try the vehicle wont turn or make any noise. Same results each try. I verified the volts from the battery: 12.3v+ and I had the battery examined at a local auto-shop. The battery tests out good though its 3 years old.


I did do a MSD80 to 81 swap, programmed remotely.
[Attached my control unit diagnostic from Ista]

Is my next logical step to replace the starter?

[dpaul]

No. Your next logical step is to test the starter. If it is OK, the next step is to ascertain if CAS is actually putting 12 volts on the line to the solenoid - what Terminal 50 actually refers to. Actually, perhaps your first logical step is to check the ground strap between the engine and chassis.

Before going too much further, is A0B4 the only error code that ISTA is reporting? Please report them all

There are no sensors at the starter so the only measure of its operation is whether CAS can detect Terminal 50 activation. A0B4 is not that specific and can actually mean nothing more than you've been pressing the start button a lot and the engine has failed to start. Or it can mean that your CAS is fried, a not uncommon occurrence.

Testing the starter is really simple - just pull off the single, 16ga wire on the solenoid (I think it's white, not sure but you can look it up in ISTA). Use a jumper to put 12v on that solenoid terminal. Obviously, this tests both starter and solenoid but if one is bad, the best policy is to replace them as a unit.

If that works, then your problem is very likely with CAS although it could be the wiring or a connector between CAS and the solenoid. If you open the CAS up you may see a burnt component on the circuit board. Unfortunately, you cannot just pick up a used CAS and plug it in. The CAS will need to be "cloned" which you can't do with ISTA or BMW standard tools. If you need them, you can find the necessary services online. Search "BMW CAS cloning". There are also some experienced posters in this forum who are equipped to do it.