06 Suburban LTZ No Turn Signals but hazards work

Im at a near loss for what the issue im having could be.... as the title suggests, I have no turn signals but hazards work. That is, when using just turn signals ... no arrows on dash, no lights on vehicle, just ... nothing happens. When hazards are activated, arrows on dash work, all hazards all the way around vehicle work perfectly.

Things ive tried/tested/replaced ...

-swapped hazard/ turn signal relay under dash with known working ... no change in behavior (all blinkers and hazards worked when suburban relay was swapped into donor vehicle)

-swapped multifunction switch out ... no change in behavior (suburban switch put into tahoe and visa versa and everything worked in tahoe with suburban parts)

-checked and replaced all bulbs just in case

-checked every fuse i know of under hood and in dash by driver door

-checked continuity of wires from steering column -> fuse block -> bcm ... all wires have continuity and none appear to be broken in any place

From the way its acting, it almost MUST be either a broken wire from multifunction switch to bcm .. somewhere in that area ... OR ... bcm is just going bad. I personally don't feel like it would be bcm without other electrical issues, but im sure i could be wrong.

Does anyone have access to some wiring diagrams and/or pinouts for the BCM connections, the fuse block for under the dash, and or turn signal wiring in general from switch to bulb? Thanks in advance.

Charm.li will have the wiring diagrams for free.

Or you can purchase a monthly subscription of AllData DIY and download all wiring diagrams in PDF format.

I would guess that those two are separate circuits, that's why it works for the hazards only?

Was the truck working fine at some point? Or just bought it? Live in the rustbelt by any chance.

testing procedure

diagrams

I would check a few things after studying the appropriate diagrams on www.charm.li.

In addition, verifying that both of the turn signal fuses (for the body lights) are intact and have voltage through them (I didn't read the diagrams but they may or may not be in the switched circuit, so voltage might be there only when a turn signal is commanded on).

If your outside mirrors have turn signal indicators (arrows), do they light up with either hazards or turn signals?

Also check all of the trailer light fuses; those are separate circuits but have their own fuses and go through the flasher module. There is a junction block up underneath the body aft of the right rear wheel, behind the quarter panel, and that's a good place to check connections and circuits. Video of its location below:



Lastly, check the trailer 7-pin socket to make sure the contacts are clean, with no dirt or other foreign matter in that socket.

strutaeng said:

I would guess that those two are separate circuits, that's why it works for the hazards only?

Was the truck working fine at some point? Or just bought it? Live in the rustbelt by any chance.

Click to expand...

OK, ive learned that the hazards operate independently of the bcm. So my original thought that the bcm was most likely good based on the hazards working is moot. Finding this out has bumped the bcm having issues up on the list of suspects.

We just bought the vehicle, so I have limited information regarding when it last worked ... but I will reach out and ask when I get a moment. I live in alabama so it is rust free for the most part.

Fless said:

I would check a few things after studying the appropriate diagrams on www.charm.li.

In addition, verifying that both of the turn signal fuses (for the body lights) are intact and have voltage through them (I didn't read the diagrams but they may or may not be in the switched circuit, so voltage might be there only when a turn signal is commanded on).

If your outside mirrors have turn signal indicators (arrows), do they light up with either hazards or turn signals?

Also check all of the trailer light fuses; those are separate circuits but have their own fuses and go through the flasher module. There is a junction block up underneath the body aft of the right rear wheel, behind the quarter panel, and that's a good place to check connections and circuits. Video of its location below:

Lastly, check the trailer 7-pin socket to make sure the contacts are clean, with no dirt or other foreign matter in that socket.

Click to expand...

When the hazards are activated, the mirror indicators work, all 4 vehicle indicators work, and the dash lights work as they should. Currently, I have yet to get the turn signals to activate at all in any capacity, other than through the hazards. I feel like discovering the hazards work independently of the bcm was a big discovery in figuring this thing out. With the bcm unplugged and removed from the vehicle, im going to feed 12v to the turn signal wires to check the continuity of the circuits from the bcm. If the continuity checks out for these circuits, then I can almost conclude that the bcm outputs for the turn signals are not functioning properly.

I didnt think to check all the trailer fuses and what not. Will do that today. Also wasnt sure where the rear fuse box was, so thank you! As for the fuses, I believe voltage is absent those fuses until the turn signals are activated (this is at least how the hazards behave). Im not positive about that though.



Also thank you everyone for the diagrams and links. I will update after performing todays round of diagnostics.

I absolutely would swap the bcm for troubleshooting. My 04 suburban would light up the flashers any time the turn signal was used. Flashers only, no signals. Swapped in a bcm from the junkyard, forgot even what year vehicle it came from, and issue fixed.

So just to update this post with what ive learned from studying diagrams and schematics on charm.li ... the blinkers, in fact, are NOT operated through the bcm on this year. I discovered this when I completely removed the bcm from the truck to find that the hazards still worked just fine.

What i found after digging into the electrical diagrams was that the multifunction switch routed 12v from one of the pink wires coming from the ignition to the corresponding left or right blinker circuits when the switch was moved into the down (left blinker) or up (right blinker) position. For whatever reason, that pink wire was carrying 0 volts which is why I got nothing when I tried switching either blinker on. Despite not knowing the reason for the dead wire, I was able to jump 12v from another ignition switch controlled wire to the dead wire to return blinker functionality to the truck. I am satisfied with this outcome and was very relieved when I gave that wire proper voltage and the blinkers came alive. Im not losing sleep over what could be causing the dead wire, considering I followed that issue up with the nightmare of tracking down a parasitic draw that was draining the battery in a matter of hours.

After a considerable amount of time and a pile of fuses pulled from the vehicle, I finally pinpointed the culprit of the draw. The SARVC module, located on the negative wire just before the battery, talks to the bcm through the class 2 data bus network ... the same network the bcm uses to communicate with other modules, such as the radio, amp, interior lights, etc. Every 10 seconds or so, the voltage draw on the battery would dip down to about .75 mA before jumping all the way back up to ~2 mA. It would stay in this loop indefinitely until it killed the battery completely (which didnt take long). After replacing this module, the bcm would finally let all the rest of the modules fully sleep, fixing my parasitic drain completely.

I couldn't have resolved either issue without being made aware of the existence of charm.li and the users in this thread so thank you to each of you! With that said, if anyone is in the market for a very clean and fully functional 06 Suburban LTZ and lives in or near Alabama, let me know as I have one for sale now

Good work.