Depending on the tool used to measure, that measurement might be an indication a pulse is occurring. Most meters will average the voltage seen, presuming the 8.57 volts is measured at the wires stated. Cranking voltage generally indicates or implies the battery voltage measurement. If that is the case, that would indicate the battery cannot handle a 'load'.I by passed the blk/w from connector 78 to 121. The battery voltage was 12.58 v. I put one end of the test light on the negative of the battery and the other end to the blu/y wire. When I cranked the engine, the test light did not pulse. I did the same to the yel/blu wire. No pulse either. The cranking voltage when measured was 8.57 volts.
Pulse measurement is best done with a 'logic probe' or an O-scope.
Example of a 'logic probe'....
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I don't know if that is a good one or not....