Could be a bad clock spring.

 

I was hoping it’s not that, but that raised a few questions.

If it is the clock spring, how can the 12v battery cable be removed to allow airbags to discharge so the steering wheel can be removed for clock spring replacement? Pretty sure I can do the swap, just don’t want to end up towing it to the dealership!

Every YouTube video I watched requires the cable ground cable be disconnected prior to replacing. I seem to remember on a Hybrid you can’t loose the battery connection without screwing up the computer and causing a trip to the dealership to reset system to get it started. Wrong?

Also read in the Hybrid forum here that the diagnostic scan tool used in the Emissions Test can cause the computer to “relearn” system if they cleared any codes???

If so, maybe it needs to be driven some minimum amount of miles before that happens. I’ve only driven it about 65 miles since the Emissions Test.

Any and all thoughts are appreciated!!

 

I've disconnected the 12V battery on my Avalon hybrid without issue.

 

Ok mystery solved! I just went out for a couple hours of city/highway mix driving and now all functions including horn now working.
Guess the computer needed more time to relearn its self..

Thanks for the replies and willingness to help!

 

I have the same problem with my 2012 Highlander Limited. Only the horn did not work. Checked fuses (ok). The panic button sounded the horn fine (so fuses/relay are fine?). All other steering wheel convenience buttons/functions worked fine. Seemed odd that a broken clock spring would only break one function but went ahead and replaced the clock spring (with inexpensive aftermarket one). ...FWIW, disconnected negative battery terminal first! Put it all back together. Horn still does not work :-(. All other steering wheel buttons work. Not sure what to check next? What's the chance the horn/airbag unit on front of the steering wheel (that gets pushed) is bad? Anything else I can check?

Which wire connecting to the airbag/horn unit is the horn (red or black) vs the airbag? Can I jumper the horn one (with battery reconnected) to check the wiring all the way thru to the horn itself?

Perhaps it is the horn switch (inside the airbag/horn unit). I also see 4 bolts on the airbag/horn unit (see attached image). Is perhaps that center piece attached with 4 bolts the switch assembly that could be replaced w/o the entire airbag? Have to believe that would be a lot cheaper. New airbags are $700+. Used units seem to run $100-200. And with used how do you know/verify if the airbag still works?

 

Wish I could accurately answer this for you! After I put on 90-100 miles (including roughly 10 start/stop ignition cycles), it was enough to reset the computer. Everything has been working perfectly since then.

From what you described you’ve done logical elimination to diagnose. I would NEVER use any sort of jumper wires on the components in the steering column/airbag unit. Not knowing for sure which wire is for what, could be expensive and even cause an accidental deployment of the airbag.

Maybe other members here can offer more sound solutions for the problem. It may be time to have a mechanic you trust to diagnose it.

 

Wish I could accurately answer this for you! After I put on 90-100 miles (including roughly 10 start/stop ignition cycles), it was enough to reset the computer. Everything has been working perfectly since then.

Thanks. My horn just stopped working on own recently ...as far as I know (hardly ever use it so not sure exactly when it stopped working). Hmmmm, I did replace the battery 3 months ago. Could that have messed something up needing a reset?

Would a high quality diagnostic scanner (a good mechanic has) be able to see more info on what may be broken (e.g. if it's something in the computer that needs reseting)?

 

Was also wondering about the actual horn button relay too. Someone with knowledge and a voltmeter can probably check that against factory specs.

I seem to remember there are 2 fuses on mine for the horn. Didn’t know that until after the fact but look at your manual just to eliminate that. Not sure if a good scanner would show a code for just the horn unless something related has hiccuped too.

Changing the battery that long ago probably would have given the system time to relearn but I’m not that experienced with them on newer systems.

 

Was also wondering about the actual horn button relay too. Someone with knowledge and a voltmeter can probably check that against factory specs.

Do you know where the relay is located? Don't see anything like that in the fuse box (like in older cars).

I did see/check both fuses. But if the horn is working from the key fob, it seems the fuse and relay are working fine (yes?). So my problem is the ground in the steering column? If so, not sure where to check that. I suppose if I knew which connection on the back of the horn/airbag unit was the horn (vs airbag), I could theoretically test for resistance (closed circuit) across it while pressing it. But wouldn't want to accidentally be doing that to the airbag circuit . Hate to spend $100 on a used horn/airbag unit (and not be even sure if the airbag even still works).

 

I wouldn’t throw money at it (especially something used), until I knew what’s actually wrong. A decent mechanic would be cheaper to diagnose and then you can fix the issue.

 

So I also tested the voltage at both horns. When the steering wheel horn is pressed, I get 12.6V at each horn. That implies the horn switch in the steering wheel is working (is grounding the circuit sending power to the horn. The horns work (when I hit the panic button on the key fob). (Unplugged one horn at a time and hit the button to confirm both are working.) So not sure what else to check? Guess I'll see if I can find someone with a good scanner to see if that turns anything up.

 

FWIW, in the end the horn started meagerly working (weak single pitch sound) some time after replugging/testing the horn devices themselves. Decided to clean up the bolt that connected the horns to the chassis (the horn ground!). After that, one horn worked better but the second one still not at all (on either side). Bought a couple new horns. All working. So in the end it was the the horn and horn ground that were problematic. Note: The new aftermarket horns had the connector facing the side (not down like the original) so could not get one side to plug in (wire too short). So make sure you get the connectors facing same direction as the original