Hey Gents,

2008 cooper S, 174,597 miles but new motor, new starter etc etc etc 35k miles ago.

Battery CCA are normal and I hear the relays clicking when I press START. Chances of bad starter....low. Grounds were cleaned up not long ago and main ground strap changed too.

Pulled codes and found

• 2 static A10A CAS "not a fault" at 171,442
• 1 static A0B5 CAS "road speed signal fault- no signal or value" at 172,741
• 3 static AOC1 CAS "output terminal 50 short circuit or CA: Outside door handle, passenger door, rear, EPROM fault at 172,940
• 1 static A0B4 CAS "starting of the engine or CA: Outside door handle, passenger door, unknown fault type at 174,215

None of these have triggered a CEL.

Not sure what these CAS faults are about or if they indicate a failing module.

Thoughts?

 

Start with the service manual troubleshooting...

 

Thanks.

 

I just realize that this is coincident with me messing with the wiring for my oil pressure/coolant temp gauge pod which is under the knee panel. I thought I lost a connection to the pod so I was checking wires and voltages.

In the process the small Mini small gauge pod had to be unbolted.

Do you know if that small gauge pod above the steering wheel has wiring on the same circuit as the CAS unit?

 

Oil pressue & coolant temperature readings would be derived from the DME. But I don't know where the gauge pods would get their power & ground.

 

no no I mean the OEM gauge pod above the seeing wheel. if it shared a circuit with the CAS maybe I pinched a wire when I was moving it around.

 

The tachometer and CAS control unit can certainly communicate with each other via the CAN-Bus network. But you would likely get a CAN-Bus fault code if you damaged a CAN-Bus wire.

 

ok so perhaps I pinched a wire...need to check that. Too much of a coincidence that Im checking those wires moving the small gauge pod and then next day, no crank on a good battery and a quality starter that's only 30k miles old.

Ill bypass the CAS and see if the starter works too.

Thanks hommie

 

Check whether the CAS control unit sends battery voltage to the starter solenoid connector when the ignition start button is pressed.

 

will do! Thanks!!!

 

​​​​​​​A10A
No crank; immobilizer issue, communication fault or timeout issue between the CAS module and DME. Causes: low battery; hit large pothole and ACSM cut power to the engine as safety measure.

A0B5
Usually a bad wheel speed sensor

A0C1
No crank; points to issue with CAS outputting voltage for Terminal 50, which is the signal that activates the starter motor. Causes: Faulty Starter Motor or Solenoid, Failing CAS Module, Low Battery Voltage. Although Terminal 50 doesn't have a direct fuse, check CAS fuses (F34 and F49 in JBE).

A0B4
No crank; indicates problem with starter operation or CAS, which handles ignition and immobilizer functions. Common causes include a faulty starter motor or solenoid, a bad CAS module, immobilizer issues (like a bad key transponder), or electrical problems like a weak battery or damaged wiring.

 

Where did you get those details? Me like.

Turns out the battery was "weak" 395CCA of 650 (its a 2 year old AGM battery) and I've had it on a trickle charger since Friday night. Haven't had time to mess with car but will check all of that.

Car takes lots of short trips so not surprised its weak.

 

I did a quick check at the starter solenoid and I do get battery voltage when I order l press the start button but I forgot to load the circuit to see if it could carry the load. I'll do that next

Assuming it can carry the load, either the starter is dead or I have a bad ground or power wire.

 

Use the voltage drop test with circuit under load to test both positive and ground sides of starter circuit.

 

That mechanic is forcing the starter to work by bypassing the relay but the cooper's starter relay is integral to the passenger side fuse panel correct?

 

Good question...

I believe the starter relay is integral to the CAS module and is responsible for sending terminal 50 voltage to the starter solenoid.

At this juncture, do the voltage drop tests on the positive- and ground-sides of the starter circuit loaded only with terminal 50 voltage.

 

Fixed? If so, what was the solution?

 

ahhh! Its been in the garage on a trickle charger until I can run the rest of the tests tomorrow.

Now, Im asking myself, how am I going to do the voltage drop tests only with terminal 50 voltage?

 

The voltage drop test is equally effective for both low amperage and high amperage circuits.

With the starter circuit under terminal 50 load, test for a voltage drop between the + battery post and the starter solenoid connector. Then do the same between the ground battery post and a metal surface of the starter. Post your voltage drop readings.

 

When you say starter solenoid connector are asking me to the tap into the unplugged harness to see if there a voltage drop at the connector, as unplugged from the starter?

 

Ok so I used a Loadpro to test the signal to the starter by unplugging the starter solenoid plug and connecting into it and using battery ground. I got 12.163 unloaded and 11.963 loaded.

With just the voltmeter I tested battery positive to the large starter connector and got 0.00 change when trying to start the car. (Starter solenoid plugged in to harness). Seems unlikely



Then moved the alligator clip to the terminal on the stater and got 0.00 again. Kinda hard to believe I got zero voltage drop again at the starter



I'm using a quality voltmeter.




And battery negative to starter body when trying to start read 0.025v. essentially no drop of starter ground to the engine and trans.

 

When I tested battery ground to the chassis ground and to above the passenger side motor mount where the 5 year old braided ground strap bolts down, I got 0.016 and 0.020v. Essentially no drop

I then tested battery positive (power) to the solenoid stud and it went from 12.95v to negative 0.95v when pressing start. I assuming this means the solenoid is activating normally??? Is pulling down to less than zero

 

Then this is weird. I'm only getting 10.7v at terminal 50 with "key on" no load (no starting) and when I start it I get negative numbers. But when I tested the same circuit at the solenoid plug, on the start I get battery voltage.




Could it be the ground for the starter solenoid since I get 12 v at the start solenoid plug when I use a chassis ground using the voltmeter but get negative volts when using terminal 50 ground wire (via backprobe)?

 

Anyway I jumped the starter from Terminal 50 and got nothing but a click. Since the grounds are all good, me thinks this 10 year old remanufactured Bosch starter with only like 40k miles is deadskies.


I cleaned the solenoid stud (m terminal) and the battery stud (b terminal). Didnt do anything and anyway they looked pretty oxidation free.

The S terminal looked perfect inside the starter. (I used a small camera to look at the connections.)

Still don't understand why I was getting less than battery voltage at Terminal 50.

 

Your use of a LoadPro was a fantastic idea for measuring voltage drops in BOTH the starter solenoid and starter motor circuits. But I think you have misunderstood the starter solenoid and starter motor electrical connections.

Here are the LoadPro instructions: