[mcaval465]

Hi all,

I have a 2007 335i E92 AT with 160k miles currently in a no start condition due to what i think is an electrical/grounding problem. Looking for any help I can get before I take it to a shop.
I'll do my best to describe what happened and what i've done so far:

The initial problem was a sudden no start about 3 weeks ago after work. The only sign of it dying up to that point was a slow start in the morning, but i brushed it off since it was a cold day. I tried jumping initially and no luck. After a bit of research I read about grounding straps breaking and got it to start by connecting the jumper across the chassis ground to the engine. Unfortunately my house was about an hour away, and since the battery couldn't charge about 3/4 the way back things started to act crazy since voltage was probably dropping. I ended up having to cruise to a stop roughly 1/2 mile from my house since the ABS and the trans were giving warnings and everything was flickering off. At that point a friend and I just slowly towed it back using some straps, putting it in neutral, and connecting it via the tow hooks to another car. (in hindsight just getting a tow back originally rather than jumping it might have saved me from further electrical issues but in the moment it seemed like the way too expensive option) Below is the list of the things i proceeded to change/check with no luck:

I immediately replaced the engine ground strap. Before, when i pressed ignition, there was no sound coming from the starter/solenoid. After replacing, you could hear the solenoid/starter give a strong click and spin for half a second, but then die out.

Charged battery.

Checked OBD codes. Initially, there were tons of codes because of the low voltage at the battery. After clearing and trying to start a few times no codes popped up.

Replaced Starter. Spun it around a couple of times with a harbor freight bump starter as well to make sure it worked when it was in the car. Also proved that things are moving and the engine isn't locked

Replaced Battery. I replaced it with a BMW battery from the dealer. Since its still sitting in my garage, i havn't been able to register it. Waiting to do that at the indy shop or dealer if i can get it running.

Disconnected IBS Cable. Also read on several forums this was a possible cause.

Replaced the black CAS relay in the fuse box. I saw on youtube this was a potential solution and said why not try. Doesn't seem like a CAS problem since the dash lights up as normal when i press ignition - just has check engine light. I've also tried using my other key.

Moved it from park to neutral. I've read on other forums this is a test to see if the brake pedal sensor works which may stop the car from starting?

The most notable thing is the moment I hit ignition, the voltage drops across the entire car. From ~12.4 V to 9 V or less, you can even see the cabin lights flicker. Also notable is that the + cable that connects to the starter near the ECU and B+ post fluctuates in voltage randomly when the car is awake. It seems like when the car is awake every ~5-7 seconds it dips to 8 V and then back to 12.4 V. The other two positive posts/connections have a solid 12.4 V. I also measured from chassis ground to the engine and the alternator case and get a solid 12.4 V.

My next step is to remove the airbox again and see whats going on at the alternator and ground terminal to the starter. Any recommendations on what else i should be trying would be greatly appreciated. I believe its a grounding issue somewhere, but i'm at a loss for where since I've replaced the engine ground strap.

[Igor_M5]

Alternator voltage regulator. Buy a used alternator from a dismantler, try to find one with less mileage and newer year. First swap the VR, if that doesn't fix anything, then try swapping the alternators.

[dpaul]

Originally Posted by mcaval465

The most notable thing is the moment I hit ignition, the voltage drops across the entire car. From ~12.4 V to 9 V or less, you can even see the cabin lights flicker. Also notable is that the + cable that connects to the starter near the ECU and B+ post fluctuates in voltage randomly when the car is awake. It seems like when the car is awake every ~5-7 seconds it dips to 8 V and then back to 12.4 V. The other two positive posts/connections have a solid 12.4 V. I also measured from chassis ground to the engine and the alternator case and get a solid 12.4 V.

The telling symptom is the voltage drop when you place an electrical load on the system. Since you've already dealt with the most likely cause, the engine ground strap, the next most likely problem is a B+ supply line.

The most common failure mode that fits your symptoms would be corrosion on the positive battery cable from the distribution block on top of the battery to the pass-through located at the bottom front of the battery box. Water entering the battery box from leaks involving the trunk, tail light or gas filler neck seal can cause this problem. Pull your battery and inspect - wiggle the lead. That distribution box/fuse box on top of the battery may also be a culprit.

Would help to know the exact build date of your car as the specifics of the power distribution varies. Look it up yourself at www.newtis.info

I would not buy an alternator or voltage regulator as suggested above.

[mcaval465]

Thank you for the responses. I replaced the voltage regulator since it was a relatively cheap part to get and also checked the B+ supply line with no luck. After struggling a bit more i decided to take it to shop to diagnose it...

Turns out the CAS module burned up. After taking it out and looking at the PCB you can see a huge burn mark on it. Must have been when I was driving home and the battery voltage was dropping. Luckily the CAS module still communicates, so we were able to pull the data from it and marry a new one to my ECM. Still not a cheap fix, but better than a whole new ECM+CAS+keys.

[brandon-335i]

Hey I’m have a simmer problem my mechanic said that I have ground and continuity but there is no positive single 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

[mweisdorfer]

Originally Posted by mcaval465

Hi all,

I have a 2007 335i E92 AT with 160k miles currently in a no start condition due to what i think is an electrical/grounding problem. Looking for any help I can get before I take it to a shop.
I'll do my best to describe what happened and what i've done so far:

The initial problem was a sudden no start about 3 weeks ago after work. The only sign of it dying up to that point was a slow start in the morning, but i brushed it off since it was a cold day. I tried jumping initially and no luck. After a bit of research I read about grounding straps breaking and got it to start by connecting the jumper across the chassis ground to the engine. Unfortunately my house was about an hour away, and since the battery couldn't charge about 3/4 the way back things started to act crazy since voltage was probably dropping. I ended up having to cruise to a stop roughly 1/2 mile from my house since the ABS and the trans were giving warnings and everything was flickering off. At that point a friend and I just slowly towed it back using some straps, putting it in neutral, and connecting it via the tow hooks to another car. (in hindsight just getting a tow back originally rather than jumping it might have saved me from further electrical issues but in the moment it seemed like the way too expensive option) Below is the list of the things i proceeded to change/check with no luck:

I immediately replaced the engine ground strap. Before, when i pressed ignition, there was no sound coming from the starter/solenoid. After replacing, you could hear the solenoid/starter give a strong click and spin for half a second, but then die out.

Charged battery.

Checked OBD codes. Initially, there were tons of codes because of the low voltage at the battery. After clearing and trying to start a few times no codes popped up.

Replaced Starter. Spun it around a couple of times with a harbor freight bump starter as well to make sure it worked when it was in the car. Also proved that things are moving and the engine isn't locked

Replaced Battery. I replaced it with a BMW battery from the dealer. Since its still sitting in my garage, i havn't been able to register it. Waiting to do that at the indy shop or dealer if i can get it running.

Disconnected IBS Cable. Also read on several forums this was a possible cause.

Replaced the black CAS relay in the fuse box. I saw on youtube this was a potential solution and said why not try. Doesn't seem like a CAS problem since the dash lights up as normal when i press ignition - just has check engine light. I've also tried using my other key.

Moved it from park to neutral. I've read on other forums this is a test to see if the brake pedal sensor works which may stop the car from starting?

The most notable thing is the moment I hit ignition, the voltage drops across the entire car. From ~12.4 V to 9 V or less, you can even see the cabin lights flicker. Also notable is that the + cable that connects to the starter near the ECU and B+ post fluctuates in voltage randomly when the car is awake. It seems like when the car is awake every ~5-7 seconds it dips to 8 V and then back to 12.4 V. The other two positive posts/connections have a solid 12.4 V. I also measured from chassis ground to the engine and the alternator case and get a solid 12.4 V.

My next step is to remove the airbox again and see whats going on at the alternator and ground terminal to the starter. Any recommendations on what else i should be trying would be greatly appreciated. I believe its a grounding issue somewhere, but i'm at a loss for where since I've replaced the engine ground strap.

Did you change out the ground strap underneath the drivers side?

[brandon-335i]

Originally Posted by mweisdorfer

Did you change out the ground strap underneath the drivers side?

Hey I'm have a simmer problem my mechanic said that I have ground and continuity but there is no positive single 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

[gbalthrop]

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

"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

[gbalthrop]

Related to prior post, attached are ISTA ScreenPrints. Please let me know if any questions.
M6510a is Starter Motor. CAS Pin #22 (Black wire) of CAS Connector X13376 provides KL50 Signal,
12V+ to Starter Solenoid, via Connectors X6011/1 & X60551/2 in the E-box.
You can add 12V+ Jumper there (in E-box) to test starter, OR check voltage there during START press.

George

[brandon-335i]

Originally Posted by gbalthrop

"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

The last 7 or my vin is p101537
I have pro tool
And yea I can follow a diagram

[gbalthrop]

Originally Posted by brandon-335i

The last 7 or my vin is p101537 [2008 335i E90 built 9/2007, with AT; the ISTA documents previously attached to Post #9 above are correct for YOUR model]
I have pro tool [You are AHEAD of me -- I DON'T ]
And yea I can follow a diagram [Well, follow those in Post #9, but for anyone who would like to know & hopefully improve upon my thoughts, they are explained below ]

THOUGHTS:
0) Please let us know Fault Codes, WITH Freeze Frame Data or Details if possible, read in CAS Module Error Memory, AND DME Error Memory.

1) As stated in Post #8 above, INPA or ISTA will SHOW you if the INPUTS to the CAS Module, related to Gear Selector Lever Position and Brake Light Switch Activation, are being received. Those are REQUIRED to Activate Terminal 50, to Send Start Signal (12V+) to Starter Solenoid.

2) I will attach screens from INPA and ISTA related to those signals to NEXT Post. I do NOT know IF Pro Tool can display CAS receipt of those signals or NOT, but I assume it CAN. I cannot tell you HOW to access that info, so if your Manual does NOT clearly indicate how to do that, please consult BG Support.

3) You can of course use a mirror or helper to monitor your brake lights. They SHOULD light when you press the Brake pedal with ONLY the Remote Key in the Insert Compartment (do NOT press START). The brake lights are powered by CAS "Terminal R" which also turns on Radio when Key is Inserted. So you can confirm Terminal R activation and Brake Light Switch Function WITHOUT any Diagnostic Tools. That does NOT mean CAS is getting the Brake Light Signal though. ONLY reading input as received by CAS "Nails" that fact.

4) You can ALSO determine function of the Gear Selector Switch without Diagnostic Tools:
a) Press Start (without pressing Brake) to turn on Ignition;
b) Note that Light next to "P" on console next to lever is lighted; Also NOTE Gear Display on Instrument Cluster; if EITHER is missing, you have a problem;
c) Press Brake and release button on shifter and move from "P" to "N"; Note proper lighting of Gear Indicator Light next to "N", and Cluster Gear Display;
d) Once again, those lights/displays indicate the Switch is operating properly and the Bus is carrying Gear signal to Cluster; that does NOT confirm that CAS is getting the signal; ONLY reading/displaying input as received by CAS "Nails" that fact.

5) INPA or ISTA allow you to OBSERVE the KL50 or Terminal 50 Voltage signal (or lack of it) being sent to the Starter Solenoid when START is pressed with foot on Brake. Screens showing that are attached to Next Post. Same drill: see what similar information Pro Tool can show you. What YOU are looking for is KL50 Voltage at the INSTANT START button is pressed with foot on Brake.

If NO KL50 Voltage (but you DO have P/N & Brake Light Switch Inputs to CAS), then there is an internal issue with the CAS Module related to KL50 relay or its activation. If Pro Tool tells you that you have ~ 10V KL50 Voltage for an instant after pressing START, but Starter is NOT being activated, you have a wiring issue in the KL50 wire (Pin #22 in diagram) and the Starter Solenoid.

Let us know what questions or findings you have related to those tests and we can suggest "Next Steps". If you can get Pro Tool to give you the needed data, please post HOW, so Pro Tool Users can learn from you. I believe there is a Thread on the "Coding" forum dedicated to Pro Tool, so you may want to search that thread.

George

[gbalthrop]

Related to Prior Post, and 2008 335i with AT, I attach the following:

I. Related to Gear Lever & Brake Light Switch Inputs received by CAS:
1) INPA > CAS > F5 > F1 > F2 Terminal Control Digital screen;
Note that "Brakes" & "P/N" circles on top row are filled. THAT indicates CAS is receiving those signals

2) ISTA > CAS Module (select from EITHER Control Unit Tree or List) > Diagnosis Scan > Inputs

II. Related to KL50 (Terminal 50) Activation & Function:
3) INPA > CAS > F5 > F2 > F1 Diagnose Terminals; This screen shows KL50 Voltage during Starter Cranking
NOTE: for some reason the two bottom bar graphs are blank; that is NOT the case with "Mike's INPA" where
KL50RS is ~ same as KL50L and Amps is in 10.xx range; 2nd page also shows Engine RPM during Cranking (~180)

4) ISTA > CAS > Diagnosis Scan > Terminals > Voltage Terminals, General
This Screen shows KL50, Volts & Amps; ScreenPrint was made with Ignition ON, START NOT pressed
Voltage & Amps values SHOULD appear on respective lines when START is pressed w/Foot on Brake

George

[Makoa6]

I was reading up on this post and following the comments when I came to the end, the user that posted this question didnt follow up with an answer. I am just curious to know if the user was able to solve their problem/issue. I am also curious to know what was the end result into fixing this issue? I love the detailed explanations and pictures to follow up with that. would love to see follow up comments of fixed or unfixed results...

[Phaay]

Perhaps its the alternator or the battery my friend had similar problem on his e46

[BMW DOCTOR]

Ditto!

[onlyinaz1]

Originally Posted by gbalthrop

THOUGHTS:
0) Please let us know Fault Codes, WITH Freeze Frame Data or Details if possible, read in CAS Module Error Memory, AND DME Error Memory.

1) As stated in Post #8 above, INPA or ISTA will SHOW you if the INPUTS to the CAS Module, related to Gear Selector Lever Position and Brake Light Switch Activation, are being received. Those are REQUIRED to Activate Terminal 50, to Send Start Signal (12V+) to Starter Solenoid.

2) I will attach screens from INPA and ISTA related to those signals to NEXT Post. I do NOT know IF Pro Tool can display CAS receipt of those signals or NOT, but I assume it CAN. I cannot tell you HOW to access that info, so if your Manual does NOT clearly indicate how to do that, please consult BG Support.

3) You can of course use a mirror or helper to monitor your brake lights. They SHOULD light when you press the Brake pedal with ONLY the Remote Key in the Insert Compartment (do NOT press START). The brake lights are powered by CAS "Terminal R" which also turns on Radio when Key is Inserted. So you can confirm Terminal R activation and Brake Light Switch Function WITHOUT any Diagnostic Tools. That does NOT mean CAS is getting the Brake Light Signal though. ONLY reading input as received by CAS "Nails" that fact.

4) You can ALSO determine function of the Gear Selector Switch without Diagnostic Tools:
a) Press Start (without pressing Brake) to turn on Ignition;
b) Note that Light next to "P" on console next to lever is lighted; Also NOTE Gear Display on Instrument Cluster; if EITHER is missing, you have a problem;
c) Press Brake and release button on shifter and move from "P" to "N"; Note proper lighting of Gear Indicator Light next to "N", and Cluster Gear Display;
d) Once again, those lights/displays indicate the Switch is operating properly and the Bus is carrying Gear signal to Cluster; that does NOT confirm that CAS is getting the signal; ONLY reading/displaying input as received by CAS "Nails" that fact.

5) INPA or ISTA allow you to OBSERVE the KL50 or Terminal 50 Voltage signal (or lack of it) being sent to the Starter Solenoid when START is pressed with foot on Brake. Screens showing that are attached to Next Post. Same drill: see what similar information Pro Tool can show you. What YOU are looking for is KL50 Voltage at the INSTANT START button is pressed with foot on Brake.

If NO KL50 Voltage (but you DO have P/N & Brake Light Switch Inputs to CAS), then there is an internal issue with the CAS Module related to KL50 relay or its activation. If Pro Tool tells you that you have ~ 10V KL50 Voltage for an instant after pressing START, but Starter is NOT being activated, you have a wiring issue in the KL50 wire (Pin #22 in diagram) and the Starter Solenoid.

Let us know what questions or findings you have related to those tests and we can suggest "Next Steps". If you can get Pro Tool to give you the needed data, please post HOW, so Pro Tool Users can learn from you. I believe there is a Thread on the "Coding" forum dedicated to Pro Tool, so you may want to search that thread.

George

I have ~10v when I press the start button it clicks but does not crank what do I do next to figure out why or how to fix it?

[Daaaaaaaan]

10V where and 10V when?

[Mack261]

did you say no power to starter? do have airbag warning light on? you might need new postive battery cable