Using ohms law, which applies in EVERY situation, you can calculate resistance as low as .001 ohms. Suppose, for example, you have a no crank condition, and the resistance between the battery post and the battery cable end shows 0 ohms on your meter. Now, suppose you check the voltage between the battery post and the cable end while attempting to crank the engine, and you see 3 volts. If you assume that the starter, for example, draws 100 amps at initial crank, you have just determined that the three volt drop has measured a .003 ohm resistance. Does your meter have that resolution? You are now duplicating the conditions in which the problem has occurred. The resulting voltage drop at the battery has now provided the starter with 9 volts, making a cranking condition difficult at best. THAT is why I suggested checking the voltage between the BMS negative and the battery negative. You are correct in saying that you cannot measure a voltage potential where there is none. If, however, you check the voltage between these points, and you find the .6 volts, VOILA! It appears that you have a voltage drop somewhere, and, as was stated earlier, you may be overlooking the simple. The light on the dash is indicating something wrong, and using the same method the computer uses to find the problem will make troubleshooting easier. You mentioned that you checked the voltage at the BMS and the voltage at the battery positive. You can do the same thing at the negative side, and you are then covering ALL of the bases. Let is know... Ray