Thread: How should I locate b13 main harness body grounds?

I have noticed that some non engine related electronic wiring, seem to have poor ground. I've looked in to the fsm on page EL-190 and shows where the main harness "Body ground", are. But I am not best with reading schematics or can visualize what those three little pictures try to tell.

What I am looking for is to make the interior light, automatic door locking mechanism and radio, work properly again. Page EL-103, I was able to find 'M1' and 'M50', body ground. From this page it seems logical that those defunct accessories, are having trouble to get some current. And, since I did treat my engine grounds, I can be sure that my 1993 Nissan, has poor ground connection for it's main harness.

I have made a picture, where you can see "M1 Body ground", "M50 Body ground" and "M54 Body ground (For anti-lock braking system). It wasn't hard to get to the M54 body ground. While I can't tell from this picture, that there are actually three connections made to that specific point, which are a big copper one, and two smaller brass, where one of those brass ground, is connected to the anti-lock braking ecu.


M1, M50, and M54 Body ground/ M54 Body ground (For anti-lock braking system)

Could someone please give me some directions, on how to reach M1 and M50. I've noticed the three smaller drawings, but I am not able to understand at what point of my car, this would be. I've searched several fora and I couldn't find a topic or a sticky topic. It would be great to hear from someone with experience.

Looks pretty self explanatory.. remove the plastic panels by your feet and you should find them, other grounds to check and clean are located in the engine compartment by the headlights and over flow bottle

While I was staring at the little picture about 'M54', I also wondered, why I found three body ground wires at one location, "on the position of M54". And now I have learned, by taking a picture, that what I meant, that I've found those wires at the location of "M50". I have included a photo and now I can tell that the little picture of 'M50', is what I have photographed. I understand now why I found three wires, while I was looking for one.



But to find the grounding point on the driver side, I had no luck. Could someone please provide me some guidance, on what is shown in the little top left picture, just below the text 'M1'?

One of my B13s had that issue with the radio and dome light going off randomly at the same time, IIRC it was just a dash fuse that needed higher amperage ..

M1 looks to be to the left of the hood latch pull, behind the kick panel.

LoL, yea don't do that!

@BenFenner, I see now, with looking fo the third time, I've found it's location. I've been looking in the wrong place before somehow, and I didn't get it that that is a hood latch, it seemed like a piece of ducting to me.

@Storm88000, thank you for mentioning. While I still want to make sure all the grounds on the car are working properly, I did overlook fusing, because this problem I've had was sitting there for a long time and now I learned that the radio seems to be connected wrong because with replacing the fuse of room lamp, the room lamp started working, the radio switched on again [which is suspected by me being connected wrong], and the door lock lamp stopped being dim instead of off.

Now I am happy that those things are working again, I still have a electrical problem and I need to have a look at how the radio is connected. By reading this forum I've read both that ground for a radio is it's chassis and somewhere down below. For the latter I couldn't make sure if this ground exists or not. I've been looking in FSM at page EL-167, I see top right, for 'CASSETTE PLAYER', it has a ground which would is chassis I assume. Here is a picture;


Now my last question, regarding grounding, is there a ground besides chassis somewhere below the radio, because I couldn't find this in FSM and I'm not so sure I'm looking at the correct page. So I hope someone can tell me if this ground location exists or not.

OEM radio and cassette player is case grounded, meaning the body of the unit is directly grounded to the dash bar. Make sure your radio is properly secured to the dash bar mounting and no excessive rust/corrosion where the tabs or screws mount.

Thank you all for helping me out, electrical schemes from FSM have become more meaningful to me and now I am sure I have proper main harness grounding, I'll post another topic with an issue I have with central door locking, so this topic has been solved.

We like the 'schemes'... bring on the schemes!