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How to access starter to measure current draw? (A0C1 CAS Output, terminal 50 )

7K views 36 replies 5 participants last post by  SunglassesGuy 
#1 ·
I've got a no crank situation. Can hear starter solenoid click once when I push the start button. A section of the ISTA+ test plan says to measure current draw from starter. Is there a place to do this other than the starter? Can the starter be accessed very easily to do this?
 
#3 ·
Place the current meter on the battery Negative terminal or around the GRAV lead by the right engine mount arm.

Clean all B+ battery terminal points from the battery to the engine compartment jumping point>to the front capped nut junction>to the rear capped nut(positive wire is inside the main wiring loom plastic protective housing)>to the starter B+ feed thick red wire, theses point are HOT all the time, and should have strong connection for strong battery voltage and current to flow and kick the starter motor connection. The final starter B+ positive connection must be cleaned and tightened.

For Ground, make sure the battery Negative cable is cleaned and tightened. GRAV lead is not loose, damaged burned, or corroded.

Use Scotchbrite or fine sand paper to clean the connections.

Once you test the starter B+ final connection and it has battery power not less much from measuring at the battery direct positive terminal, next test battery at the braided wire on the body of the starter with start up button pressed (solenoid click) you should also see battery charge, if you have both battery power on these two points replace starter.
 
#4 · (Edited)
Thanks Guys. Gonna take me a few days to try all this, was simply trying to move the car so I could work on wife's car. Do you see anything in these ISTA read outs that point to a problem.

BTW - Where is this mysterious Terminal 50 located?

Starter Enable = Not active? Does this only go active when the start button is pushed?
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Terminal 50E 0.0V , Terminal 15 , Wake up (ACC) = 0.13V ?

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#6 ·
Where is the circuit that activates the starter solenoid? I've gone thru ISTA verbatim and can't find it. Terminal 50 ends at the DME, and can't find it traveling over to the starter solenoid?
 
#8 ·
CAS activate the the starter circuit, the starter relay is built inside CAS, if you hear the starter solenoid clicks means the starter KL50 circuit is activated and you will find 12V power is sent to the starter solenoid, gain access to the starter solenoid you will find a plug connected to the solenoid. Next stage is connecting the B+ to the starter motor to turn it as I mentioned in my previous post, test the 12V points where the starter motor should turn, when 12V verified and the the starter motor stuck hit it with a mallet and try to start.
 
#11 · (Edited)
Thanks again Guys, I'm working with a 2009 M6, but it looks like the last circuit diagram that ZiMMie posted matches (Numbers are a bit different, but basically same circuitry). My version of the TIS just didn't show the starter details, this is very helpful. Another thing that is a little different is the CAS/DME pins. Correct me if I'm wrong but it looks like for the M6, CAS Terminal 50 connects to Pin 2 of the DME at the 60001 connector?

I will measure voltages and resistances and try the hammer whack. Was also wondering if I put the car in gear, and just push on it a bit, maybe that would accomplish same thing as hammer whack. The starter was replaced a few years ago, just before I bought the car. I have no paper work to verify that tho.

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Is there a way to attempt to easily jump these two points (In Red) so I don't have to tear plenums off to access the starter? (Oh and do it with out burning some electronics out along the way?) I've been wondering when people open up their CAS and find a burnt Terminal 50, its because they tried to hotwire the car by connecting B+ directly to the starter solenoid, which would send B+ back to Terminal 50 area.

One other question: What is going on inside the Starter at #4 ? This looks like a switch, what opens and closes it? And what do the little rectangles with a slash thru them represent? (items #2, 3 inside the starter)

EDIT: Think I found the answer to the Starter components question: 6 Complete Starter Solenoid Parts, Functions & Working: ECE

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#12 ·
Don't jump items in red, you don't need, that signal is available at the starter signal line plug that's connected to front of the starter (solenoid), by the way, if you pulled that connector you isolate CAS.

Don't complicate things, I know we all hate to remove intake plenums but for this you need to to troubleshoot the starter easily and safely. You only need to measure 12V at the B+ with ignition off and the braided wire with start button pressed, if both are having 12V it is the starter, either whack it or replace.

Forget about the DME terminal KL50 signal, it is only a reference signal.
 
#13 ·
Thanks guys. Gotta rebuild my wifes brakes - new calipers, replace rotor, pads and bleed the system. Hopefully I'll get her brakes done by Tuesday (hopefully Monday) and then do some testing on the M6 next week.

I did have some friends help me move the M6 over to the other stall so I can get wifes car onto the lift. So tried to nudge the M6 while in gear. Didn't help.

Platii BTW - Why whack the starter? Are you wondering if something inside the starter could be stuck?
 
#15 ·
new info: Terminal 50E reads 11.8 V when pressing start and terminal 50L reads 53 Amps
 
#16 ·
I chased this code and no crank condition on my 6MT for a while, it was the starter. Replaced it from the top, not a terrible job. Fine ever since, it’s been over a year.
 
#17 ·
I saw a DIY on this, apparently there are 2 methods, one actually remove the entire starter, and one, leave housing in place and replace guts. Which did you do? Also, starter was supposedly replaced about 2 years ago, just before I bought car. I have no documentation to prove tho.
 
#19 ·
I left the housing and replaced the guts. 2 year old starter should be fine though… interesting. Good luck with the diagnosis
any major difficulties that you recall as you replaced the guts?
 
#21 · (Edited)
Thanks N_Rob.

I'm getting some confusing info, maybe my meter isn't fast enough to keep up.

SCENARIO #1: When using ISTA : Terminal 50E reads 11.8 V when pressing start and terminal 50L reads 53 Amps

SCENARIO #2: However, when I read the battery Voltage at the starter solenoid connection voltage seems to drop to zero. Also not reading any current draw off the battery.

Measure at starter : 12+ volts, drops to 0
Measure at the jump location of B+, 12+ volts, drops to 11.85V

Does this mean anything or does ISTA Terminal 50E and 50L tell me all I need to know?


The ISTA test procedures says to read at battery and if SCENARIO #2 occurs, replace the CAS module as shown below.................


HERE IS SCENARIO #2 ISTA Test below

Step 1
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Step 2
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Step 3

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This is I'm measuring for SCENARIO #2

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#23 · (Edited)
Plenums off, measuring here: Voltage drops to 0.6V when start is pushed. This is between this point (blue) and ground.
If I measure from this point (blue arrow) to the battery jump connection (the positive side of where you charge the battery), it measures 0 volts and when I push the start button it measures 11volts. (my battery is a little run down from testing)
Which one should I be measuring?

I'm not finding loose battery cables.

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WHEN MEASURING BETWEEN THIS POINT and Ground, voltage only drops to 11.85. BTW - how do you remove that little black bolt cover that is shaped like a nut/bolt. It is 17mm in size, and covers the battery cable connection where the arrow points?


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#25 ·
I forget now, car is not where I live, so I can't run out there and get it real quick. How should I be taking these measurements?

#1 or # 2 (or both) ?


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#26 ·
You've already found the issue. The solenoid top cable should not drop to zero when starter is enabled. Remove that cable and clean the terminal and tighten that nut again. Do the same on the other end of the wire, which from memory is the black plastic nut where you measured 11.85V. That black plastic nut is really a nut. Use a wrench and get it off.

If memory is wrong then that cable goes to the alternator itself but I don't think that's right...
 
#27 ·
You've already found the issue. The solenoid top cable should not drop to zero when starter is enabled. Remove that cable and clean the terminal and tighten that nut again. Do the same on the other end of the wire, which from memory is the black plastic nut where you measured 11.85V. That black plastic nut is really a nut. Use a wrench and get it off.

If memory is wrong then that cable goes to the alternator itself but I don't think that's right...
Thank you, everything looks very clean, no corrosion, but I will do that. Even the braided wire is shiny copper. And thanks for the black nut answer! Its on there pretty tight, didn't want to break anything.

What should be the reference for measuring these voltages? Should it be between solenoid top cable and ground?
 
#29 ·
Ok, will measure braided wire. I think what is happening, is when I push the start button, I hear a plunger or something move. When it moves, voltage drops to zero. So something must be short circuiting to ground at that point?? What would that be? And why does voltage not drop to zero at other points along that same circuit?

(I have video recording of plunger sound if that helps)
 
#30 ·
Check the braided wire to see how the starter internal circuit function. Seems the starter is internally shorted or stuck, have you tried to whack it?. Or a weak battery, have you tried different battery or jump it with another car?.
If the 12V B+ voltage drop when you initiate starting, try to remove that cable from the starter path and see if the voltage drops. You can isolate the starter by removing the 17mm plastic nut either the forward or the rear ones to check the voltage drop, just cover the B+ cable terminal when you remove and not to touch the chassis or it will spark.
 
#31 ·
I've tried a few whacks, but haven't moved cable housing out of the way yet to give it a really good whack. So far, the whack has been on the top of the starter. I put a pipe on the starter, then whacked pipe with hammer. Wonder if turning the engine might help as well?

Also, yes, put my 545 battery into the M6 and still no crank - same results.

It looks to me that the 12V B+ on starter travels directly from starter to the jump location (left side shock tower). If I remove one of the 17mm plastic nuts, it will remove power from 12V B+ at starter. Did I overlook something?
 
#32 ·
In the engine bay picture at front of the engine main wiring loom plastic cover the front connectors are removed, Did you just removed them?. Is there any other wirings removed?.
Wonder if turning the engine might help as well?
Not sure if it will help stuck the starter, for the starter to turn with transmission in gear the "plunger" must be extended as you mentioned earlier
OR
Prepare to turn crankshaft with 32mm socket at front, extend the plunger and crank the engine with a ratchet or a long bar to see if it is stuck (to do this safely you need to disconnect the battery B+ cable form the starter path by removing the 17mm nut, isolate the cable going to the starter, or the engine will turn and might start when the starter got unstuck).
It looks to me that the 12V B+ on starter travels directly from starter to the jump location (left side shock tower). If I remove one of the 17mm plastic nuts, it will remove power from 12V B+ at starter. Did I overlook something?
I already explained this in post#.3. The battery/charging cable comes all the way from the battery to the jump point and then spliced to the front 17mm nut and spliced to the starter and to the alternator.
 
#35 ·
Mystery solved guys! Thanks for all your help!! Turns out a loose bolt at the rear of the battery feed that runs thru the wire housing under the plenum. The bolt that holds the starter branch of B+ was loose inside the housing (platti - yes, it was me that removed some of those connectors, I had started taking the wiring apart last night so I could look thru all of it).

The measurements taken at the starter before finding this were:

Starter B+ = 0V when start button pushed, 12.2 V when not pushed
Starter braided wire below = 0.65 V when start button pushed, 0 V when not pushed.

The cable must have been just loose enough to not allow current to flow

The old girl even fired up for about 5 seconds before her computers realized all the connectors were off. She is wanting to go somewhere. Oh how I missed the sweet sound of her S85 !!

Thanks Guys!!
 
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