B1101 Code No power to Start Relay
06-10-2018, 07:15 PM
#1
Junior Member
Thread Starter
B1101 Code No power to Start Relay
Car has been running fine until a couple days ago when I get in and it will not crank. Key goes in and out without issue and turns back and forth in all 4 positions with no discernible issues and no messages in the LCD.
1. Battery is at 12.55V and passed a load test. 12.55 v should be plenty so it is not causing this problem, correct?
2. I found one bad fuse but, replacing it did not cure the problem.
3. iCarsoft reader gives a B1101 Code "Fault in CAN communicating with control unit N 47-5 (ESP, SPS and BAS control module). In searching this site, I only see 2 posts with that code and neither seemed helpful. Where is N 47-5?
4. Fuse 52 (starter relay) does not have power to it. Relay S tests okay when removed and checked. No power at the plugs for the primary side.
5. I found a chart called "Tip Start Activation" but, I am having a hard time figuring out just what it means. Is ECT for engine coolant temp? What is CKP? What is P/N in this context? Am I correct that the CAN is the black box pictured at the top center? Where is it located on the car?
Thanks for any help anyone can give.
1. Battery is at 12.55V and passed a load test. 12.55 v should be plenty so it is not causing this problem, correct?
2. I found one bad fuse but, replacing it did not cure the problem.
3. iCarsoft reader gives a B1101 Code "Fault in CAN communicating with control unit N 47-5 (ESP, SPS and BAS control module). In searching this site, I only see 2 posts with that code and neither seemed helpful. Where is N 47-5?
4. Fuse 52 (starter relay) does not have power to it. Relay S tests okay when removed and checked. No power at the plugs for the primary side.
5. I found a chart called "Tip Start Activation" but, I am having a hard time figuring out just what it means. Is ECT for engine coolant temp? What is CKP? What is P/N in this context? Am I correct that the CAN is the black box pictured at the top center? Where is it located on the car?
Thanks for any help anyone can give.
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Nathan78 (02-22-2021)
10-12-2018, 02:02 PM
#3
Junior Member
Thread Starter
Search for my other posts where I get into the evolving problems since February in more detail. I have been at this for a long time. I have almost given up many times because of the frustration of buying parts and trying different things that ended up not fixing the problem. In addition, I have been distracted by a lot of honeydo's. Ultimately, I determined I needed to take time to educate myself about how CAN works and how to diagnose. Here's an update.
First, I would encourage MB owners to consider how many things can go wrong with your car to put it in limp mode, give error codes and LCD warnings. The likelihood that you will read a post on this or any other site or watch a YouTube video that will address your problem is virtually zero. The only affordable solution will be to learn how to diagnose the problem. If that sounds like a daunting task, keep in mind that all the guys who repair MB's in shops day after day were once mere mortals, too. There is no reason that you can't learn to diagnose the problems with success, even if it takes you a lot longer. But, don't expect to grasp all they know in an hour or two. You don't have to learn CAN at the same level as a shop mechanic. They are in a business and have the advantage of knowledge that makes it profitable. Individuals have the advantage of taking as much time as is needed to figure out the problem. In the end it is like repairing anything else: If you don't understand how it works, you won't be able to diagnose/fix the problem.
Regarding the specific problems identified above:
1. The dealer tested the battery and says it is good. In another thread, a member suggests that I need to check my alternator. He apparently had a problem with a bad diode in the alternator that was interfering with the high CAN signal (which operates at under about 1/2 volt). The alternator was apparently causing noise in the CAN signals. I have a new voltage regulator to put in but, haven't gotten to it yet. That could solve almost all of the issues in my original post but, I am not holding my breath. For $30 I just wanted to make sure that potential cause was eliminated.
2. After I replaced the bad fuse per the above, I also found that the starter relay was bad. I switched it with the horn relay and the horn stopped working even though I had tested it as good previously. After I changed it, I still didn't get it to start - at least initially. At some point the start relay did start working as it should and the car now starts every time. Perhaps the car had to go through a series of CAN signals to figure out which components were working. I also went through and manually erased all the codes from each module in the car. At some point the start relay started working again but, I couldn't say exactly what I did that fixed it. I think the most likely culprit was the relay.
3. N47-5 is the ABS/BAS module. I understand that if it is bad, the car should still run and the brakes just revert to a non-ABS status. If that is not correct, someone please say so. I am inclined to believe my module is bad but, I need to test it as a CAN module which i have not done yet but, will soon.
4. I understand that the start fuse will not have power to it unless the universe in which it operates is aligned. Shifter in P or N. Temperature in normal range. Etc. Where it did not have power before, it now has power and the car starts fine. See #2 above.
5. CAN is not a black box or any other module. It is the network of twin wires (twisted together) that are connected between all of the components that need to "talk" with each other along with the module to which the wires are connected. In my C230, CAN C provides communication among engine-related modules; CAN B provides communication among modules in the interior. Each module has a transceiver so it transmits signals for other modules on the CAN to "hear' and it receives signals from other components in the CAN. When a module can't hear the signal from one that its program says it must talk to, you get an error code. In my C230 the ignition switch operates as a gateway to allow some signals to go between the two CAN circuits. EVERY MB owner that works on their own car needs to have an understanding of how the CAN systems operate. Without that, you will have a hard time deciphering and diagnosing what your error codes mean, unless they are the simplest kind (like a tail light out). Even with an understanding of CAN, it can be difficult, at times, to figure out the real culprit - such as with the alternator issue in #1 above. Be forewarned; this is not for whimps. When I read this stuff the first time, it made my head hurt. But, once you think about it for a while - and realize that you are driving around in a pretty complicated computer network with wheels - it will begin to make more sense. The sad truth is that without understanding how the CAN network in your car works, you will have little chance of fixing anything but the most simple problems. I ended up buying a book on CAN theory which was somewhat helpful. Here are a couple of the websites from which I got the most help.
https://www.scribd.com/doc/138758517...nz-Can-Network (the document that comes up is downloadable if you sign up for a 30-day trial. I got a second copy from another member, as well) This is an MB-specific document and gives a very good explanation.http://www.esd-electronics-usa.com/S...ting-Guide.pdf https://www.esd-electronics-usa.com/...roduction.html
First, I would encourage MB owners to consider how many things can go wrong with your car to put it in limp mode, give error codes and LCD warnings. The likelihood that you will read a post on this or any other site or watch a YouTube video that will address your problem is virtually zero. The only affordable solution will be to learn how to diagnose the problem. If that sounds like a daunting task, keep in mind that all the guys who repair MB's in shops day after day were once mere mortals, too. There is no reason that you can't learn to diagnose the problems with success, even if it takes you a lot longer. But, don't expect to grasp all they know in an hour or two. You don't have to learn CAN at the same level as a shop mechanic. They are in a business and have the advantage of knowledge that makes it profitable. Individuals have the advantage of taking as much time as is needed to figure out the problem. In the end it is like repairing anything else: If you don't understand how it works, you won't be able to diagnose/fix the problem.
Regarding the specific problems identified above:
1. The dealer tested the battery and says it is good. In another thread, a member suggests that I need to check my alternator. He apparently had a problem with a bad diode in the alternator that was interfering with the high CAN signal (which operates at under about 1/2 volt). The alternator was apparently causing noise in the CAN signals. I have a new voltage regulator to put in but, haven't gotten to it yet. That could solve almost all of the issues in my original post but, I am not holding my breath. For $30 I just wanted to make sure that potential cause was eliminated.
2. After I replaced the bad fuse per the above, I also found that the starter relay was bad. I switched it with the horn relay and the horn stopped working even though I had tested it as good previously. After I changed it, I still didn't get it to start - at least initially. At some point the start relay did start working as it should and the car now starts every time. Perhaps the car had to go through a series of CAN signals to figure out which components were working. I also went through and manually erased all the codes from each module in the car. At some point the start relay started working again but, I couldn't say exactly what I did that fixed it. I think the most likely culprit was the relay.
3. N47-5 is the ABS/BAS module. I understand that if it is bad, the car should still run and the brakes just revert to a non-ABS status. If that is not correct, someone please say so. I am inclined to believe my module is bad but, I need to test it as a CAN module which i have not done yet but, will soon.
4. I understand that the start fuse will not have power to it unless the universe in which it operates is aligned. Shifter in P or N. Temperature in normal range. Etc. Where it did not have power before, it now has power and the car starts fine. See #2 above.
5. CAN is not a black box or any other module. It is the network of twin wires (twisted together) that are connected between all of the components that need to "talk" with each other along with the module to which the wires are connected. In my C230, CAN C provides communication among engine-related modules; CAN B provides communication among modules in the interior. Each module has a transceiver so it transmits signals for other modules on the CAN to "hear' and it receives signals from other components in the CAN. When a module can't hear the signal from one that its program says it must talk to, you get an error code. In my C230 the ignition switch operates as a gateway to allow some signals to go between the two CAN circuits. EVERY MB owner that works on their own car needs to have an understanding of how the CAN systems operate. Without that, you will have a hard time deciphering and diagnosing what your error codes mean, unless they are the simplest kind (like a tail light out). Even with an understanding of CAN, it can be difficult, at times, to figure out the real culprit - such as with the alternator issue in #1 above. Be forewarned; this is not for whimps. When I read this stuff the first time, it made my head hurt. But, once you think about it for a while - and realize that you are driving around in a pretty complicated computer network with wheels - it will begin to make more sense. The sad truth is that without understanding how the CAN network in your car works, you will have little chance of fixing anything but the most simple problems. I ended up buying a book on CAN theory which was somewhat helpful. Here are a couple of the websites from which I got the most help.
https://www.scribd.com/doc/138758517...nz-Can-Network (the document that comes up is downloadable if you sign up for a 30-day trial. I got a second copy from another member, as well) This is an MB-specific document and gives a very good explanation.http://www.esd-electronics-usa.com/S...ting-Guide.pdf https://www.esd-electronics-usa.com/...roduction.html
Last edited by Gem Stater; 10-12-2018 at 02:08 PM.
