Here Is An Update On the 09 S60 2.5t

I did Full electrical system test today on this Vehicle. I performed volt drop test on both negative and Positive circuits for Body, Alt, Starter, power supply and interior grounds. Alternator Amperage output test and Starter amp draw.

To perform a volt drop tests with a multimeter: red lead to where the source is coming from black lead to where its going to. For the starter + Ciruit we connect red to the battery and black to the hot post on the starter. for Negative, -.
red to the starter housing and black to the battery negative post.
The starter Volt drop Battery to hot post on the 09 S60 starter circuits was .34 volt while cranking the negative battery term to starter housing was .12v starter . Which is exceptional! and show there are no corroded connections or bad wiring.
example .1 volts per connection; battery to power distribution center to starter = 4 connections .4v. + .1 volt per 3 ft of wire; (14 feet of total wire) + .466v total acceptable allowance is the sum of .86Volts while cranking the engine.
for checking The starter solenoid; motor feed side of the starter solenoid add .1 v for the terminal connection .2v for the contact disc inside of the solenoid total sum of .3v is normal target. This vehicle had a reading of.6 volts when measured between the hot post and the starter motor feed post. showing compromised internals
The Ignition Circuit Reading at the S terminal: Muilti Meter leads; Red to + pos. Batt Post. Black lead to the S terminal. was .3 which is more than acceptable using the same formula. the relay counts for .1 volt in additon to wires and connections.
The starter Amp draw should be around 125 amps to 150 amps the subject car had a reading of 301amps peak (initial) 270amps steady amps draw.
the amps reading was way to high the starter was also cranking at a slower RPM
I replaced the Starter Motor, the new part had a 110 amp draw avg..

The check Engine light so far has stayed off now. we will see what tomorrow brings.

For the Alternator circuit the acceptable Volt drop allowable is 10% of the alternator output when the alternator is at full load. EG: a 140 amp Alternator x .10 = 1.4 volts . 1.4 Volts Volt drop is the Maximum allowable volt drop. You Add the sum of the Positve+ and the negative- readings. Multimeter Leads For the alt circuit Volt Drop; Positve circuit:Red to Alt + Positive post, black to positive battery post. Negitive circiut ; Red lead to alternator housing black to the _ Neg Post. Put the fuel pump fuse back in, Start the car, have assistant run the rpms steady just over 1500 rpm. Load the alternator (with a CARBON PILE just load the alt to peak out put very briefly) easiest is to take the reading right after cranking for the starter circuit V/D test, turn on all all lights and accessories to load the system.
On this S60 the positive reading Was .56 Volts The Negative Reading was .18 for a total volt drop of .74 volts it is equiped with the 160 Amp Alt X10% = 1.6 volts total The Alt Wiring & connections are good since my reading was Just under half of the max allowable. the Voltage output was 14.2 volts, Perfect!
once you do these test, it goes easier Volt drop test will help from changing parts that are ok and pinpoints the problems

If the checkeng light stays out my deduction is: the excess starter draw was dropping all systems volts below normal threshholds programmed was the root of the C/E Light No Codes