Quote:
Originally Posted by brandon-335i
... my mechanic said that I have ground and continuity but there is no positive signal to the starter for it to turn over. When we use a probe and give it power it starts fine does this sound like a cas problem or something else
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"Terminal 50" of the CAS Module is a relay which sends the "Start Signal" (12V+) to the Starter Solenoid to "Activate" the Starter. BEFORE that signal can be sent, If you have an MT, the Clutch Switch needs to be activated by pressing the Clutch Pedal, which sends a ground signal to the CAS Module.
If you have an AT, the Brake Light Switch must be activated by pressing the Brake Pedal, which ALSO sends a Ground signal to the CAS. Also, the Gear Lever Position Switch must send a CAN bus signal to CAS indicating Lever is in P or N position.
If you have either INPA or ISTA diagnostic software, you can view a screen that will TELL YOU, without disconnecting anything or using a meter, etc.:
1) If P/N signal received by CAS;
2) If Brake Light Switch signal received by CAS;
3) If Clutch Switch Signal Received by CAS;
4) IF CAS KL50 (Terminal 50) relay is sending 12V+ signal to Starter Solenoid.
Since you have to add a 12V+ "Jumper" to the Starter Solenoid to Activate the Starter Solenoid/ Motor, either (1) one of the signals needed to Activate KL50 is missing due to a bad switch or wiring fault (or even a bad CAS fuse), OR (2) the CAS KL50 Relay is bad, OR (3) the wiring between the CAS Module & Starter Solenoid (which runs through the E-box) is bad.
Someone with INPA/ISTA who knows how to use it could quickly determine what to check next. If you will let me know the following, I can suggest tests to try, even if you do NOT have BMW-specific Software/ Scan Tool:
1) Last-7 Characters of your VIN;
2) Make/Model of any Scan Tool or Diagnostic Software available to you;
3) If you have a Multimeter and can follow a wiring diagram, at least if conventions & symbols are explained.
I attach ISTA ScreenPrints of the CAS wiring diagram and Component Locations for 2008 335i to next post, so as NOT to ruin margins here.
George