Chevrolet Malibu Forums banner

1 - 20 of 20 Posts

·
Registered
Joined
·
43 Posts
Discussion Starter #1
Gents; Struggling with the wiring issues on my boy's Classic. The upper brake light along with the two lower brake lights r not working. Checked the 15 amp fuse which is ok. I purchased a wiring diagram from Mitchell for $20 bucks but there are a lot of dead ends like not showing if the wiring goes to the BCM...which I think it does.Any one of u gents can help?
 

·
Administrator
Joined
·
17,089 Posts
Can you post a picture (or pictures) of the wiring diagram? From that I may be able to help direct you.

Simply put, if the BCM manages all of the inputs and outputs, then the TS (turn signal) and brake inputs go to the BCM, then it decides which bulbs to turn on and if they are to flash or not.

Once I see that in the diagram(s), it'll make it easier to speak with more certainty.
 

·
Registered
Joined
·
43 Posts
Discussion Starter #3
DD for some reason I'm not able to do anything (print, pdf etc.) with the Mitchell wiring diagrams. I bought a one month online access subscription and suspect they suspended the print feature to get more money. I also bought a CD which should come any day. However, the BCM diagram did not show where there is control of brake or tail lights backup lights etc.I just purchased another cheap used BCM and installed it and again have the exact same problems....no locks no interior lights nor trunk light r brake lights. This is telling me there has to b something malfunctioning in one of the three fuse panels. I also discovered some of the more expensive on line wiring diagrams have a feature where u highlight a component and the entire wire trace including all the additional components light up...neat. DD I do appreciate ur help!
 

·
Administrator
Joined
·
17,089 Posts
If you can see the diagram on your screen, you can use the Snipping Tool to grab a screen shot, then save that image for later use.

Are the locks, interior lights, and trunk light not working with the original BCM as well?
 

·
Registered
Joined
·
43 Posts
Discussion Starter #5
Those clever so and so's at Mitchell somehow disable the snipping capability also. I could take a picture of the screen and paste it...since a BCM diagram is central to this issue...it is...I'll c what I can come up with, Thanks my friend
 

·
Administrator
Joined
·
17,089 Posts
That's a great picture, but all it has is the BCM connections to other systems. What I need to see is the actual brake light circuit, which may be part of the exterior lights diagram.
 

·
Registered
Joined
·
43 Posts
Discussion Starter #8
Here's the outside lamps wiring including the third brake light. All good but ends at the mysterious splice 303 can't find where wiring goes from there. Might be revealed when I get the factory manual CD. I've included the splice 303 location but not much help .....this is the first time I've been totally stumped..... wish I had a tech 2 scanner!.
 

Attachments

·
Registered
Joined
·
229 Posts
There is brake switch underneath the dashboard close to steering column right side,
DSC06070.JPG

could be not working or out of correct position.
 

·
Registered
Joined
·
43 Posts
Discussion Starter #10
I'm in the process of checking that switch now. Strangely, the fuse is fine plus the fuse holder has power to it.....where the sparks mysteriously go from there...BCM maybe.... I do not know. Thanks for the nice clear picture!
 

·
Registered
Joined
·
229 Posts
i forgot to mention that these tow switches are not in normal position i took the photo while i was doing repair for the cruise control. they should be pressed permanently only released when brake pedal pressed, for example to make it clear one time i found the brake lights on after one night in parking because of the left switch was out of its place.
 

·
Registered
Joined
·
43 Posts
Discussion Starter #12
Could very well b my issue.....the orange wire going to that switch has no voltage though but the fuse is ok....scratching my head yet again! Thanks
 

·
Registered
Joined
·
229 Posts
usually the switching function done on the dead wire meaning the closing contact grounding the signal going to the electronic board. so what you measure is zero volt referenced to ground. better to measure ohms between the switch terminals while pressing the push button, battery should be disconnected when ohmmeter is used.
 

·
Administrator
Joined
·
17,089 Posts
That diagram with figure 14 has all the electrical info I would need to track down the issue.

Your vehicle does not use the BCM to determine the flash rate. It still uses a legacy flasher, found in the upper right corner of the document. It also flashes the hazard lights when needed.

The brake light switch goes directly to the brake lights, and since you have separate turn signals, there is no other switch between the brake light switch and the lights. The only thing that SP303 does is multiply the wire providing power to the brake lights into 4 more, but uses only 3 of them. Which 3 it uses depends on the style of CHMSL you have.

Have the brake pedal held down and check the brake light switch (BLS) for power on both terminals. If found, release the pedal and see which one turns off. That is the one that will power the lights.

Hold the pedal down again and check at the taillights for power to the brake light sockets. If found, check the terminals inside the socket as well as the bulb itself. (You have 2 bulbs on each side.) If now power is found, check for power at the CHMSL if you can do so without taking apart a lot of stuff. Otherwise, find SP303 and check it.

See if you can determine which side of the socket is grounded, which means the other receives power. Then use a long wire from the battery (or jump it from the parking lights or turn signal) to apply power to the brake light socket. If the others light up, you need to provide a new path from the BLS to the brakes.

It may be as simple as finding the SP303 and repairing it.

Worst case is that you can run a new wire from the BLS to one of the brake lights and/or the CHMSL. Since they are supposed to be spliced together, getting power to one should bring power to all of them. If they don't all light up, splice into that wire and run it to the other lights.
 

·
Registered
Joined
·
43 Posts
Discussion Starter #15
....although, hard to imagine all issues happening at once, I do suspect something is awry with sp303 DD. And since I was poking around in some of the harnesses it's entirely possible I caused these issues. Thanks gents for ur patients and top notch technical help! At the moment I'm visiting my daughter for the weekend. She's buying a new Volvo SUV...will b awhile before I mess up her wiring!
 

·
Administrator
Joined
·
17,089 Posts
Hey, when I was a teenager, we had a '72 Volvo 164.

If you're afraid to mess up the wiring, lemme know and I'll find an empty seat on a jet airliner. ;)
 

·
Registered
Joined
·
43 Posts
Discussion Starter #17
I seem to recall years ago that a modern airliner went down due to the Kapton wiring shorting out and catching fire.....I hope to stay away from older airliners also!
 

·
Registered
Joined
·
43 Posts
Discussion Starter #18
DD, got home late from my daughter's.... enough sun light left though to check a couple of things in the boy's auto. Although, as I stated several times, the stop lamp fuse is good and getting power, there is no power from the orange wire at the stop lamp switch. I checked and there is a dead short in that wire....why in the Sam Hell did the stop lamp fuse not blow? I was also sent astray because I thought the BCM controlled the stop lamps....However, U, my friend, recognized immediately by looking at the wiring diagram, I furnished, the stop lamps including the high stop lamps r not BCM controlled. U r not "DD" u r the Malibu wizard!
 

·
Registered
Joined
·
43 Posts
Discussion Starter #19 (Edited)
After several not free wiring diagrams a shop manual CD...not one but two BCMs and a week of frustration, found the problem.....DD u would b proud! It was the fuse thingy next to the fuses on the left instrument panel fuse block. It is not addressed in any way on any of the wiring diagrams. I stumbled on it because I tried to get the little clear cover off to check the wires for voltage.....see attached thumbnail......While doing so I noticed the wires pulled out in their entirety so I pushed them back in.....viola....brake lights work locks work interior light and trunk lights work. However, the misses still made me sleep on the couch due to not paying attention to her ....always something to ruin my day!
 

Attachments

·
Administrator
Joined
·
17,089 Posts
Hey, congrats on getting it figured out.
 
1 - 20 of 20 Posts
Top