I am visiting my girlfriends family and her sisters 2012 has the hazard light issue (turn on randomly, flashes faster with vehicle speed, etc) She sent it to the dealership and was diagnosed with the ABS actuator short (after a $600 diag fee). She can't afford the replacement at the moment and I don't have the tools to change it up here. I have seen two temporary fixes; cutting the wire on pin 8 on L55 under the dash or snipping the HRZI wire on the abs ecu connector under the hood. Is there a preference between the two? We have to pick up her car in the morning and I need to pick one tomorrow Once she has time to come visit I'll get the actuator, reconnect the wire and get her fixed up properly. Thanks!
If you mess with L55 pin 8 you won't have hazards at all, even when you want them. If you disconnect A58 pin 10 (HZRI) you just won't have the faster-with-road-speed unwanted ones. If you just back the terminal out of the connector there (like most Toyota connectors, there's probably a primary locking lance holding the individual terminal in place, and a secondary lock for the connector that secures all the terminals), then all you have to do is pop it back in after the actuator's been replaced. Or you could leave it disconnected, as no one has yet explained why the skid ECU needs to know when the hazards are on, anyway. Or you could put a diode there, so the ECU could still know when the hazards are on (for whatever reason it wants to know that), but it wouldn't be able to flake out and make them flash.
The Repair Manual (more info) for 2012 describes the HZRI terminal of the Skid Control ECU as a “Hazard warning switch input,” but that might be an error in the documentation, if it it’s actually intended as an ECU output. It’s certainly wired that way, in the sense that the ECU can activate the hazard warning lights. The publications for 2012 models don’t discuss why this connection exists, but in New Car Features for 2016 and later models, Toyota explains, “When emergency braking, the emergency brake signal function automatically flashes the hazard warning lights in order to reduce the risk of being rear ended by a proceeding vehicle.” It may be that the HZRI output is for similar behavior on earlier models.
It's weird, though ... there's not just the description "Hazard warning switch input", but also the mnemonic HZRI. And yes, it's wired in such a way that pulling it to ground makes the hazards go on, but that seems like it'd be true of just about any way they could monitor that line as an input (other than going all paranoid about it and putting a diode there, as I've suggested as a workaround). I don't see a lot of evidence of them going to such lengths to protect other inputs in general. Mostly, I think, the ECU just isn't supposed to flake out. When it does flake out, it doesn't seem to reflect any kind of intended ECU behavior, but only that the line is being pulled down by some kind of short to the adjacent SP1 speed pulse output. This is puzzling too, though, because the distinctive thing about the hazards is that they flash in front as well as in back, and geometry already reduces the risk of being rear ended in front. So it would seem quite adequate to just flash the brake lights, and indeed the Gen 3 stop light "relay" has not one but two extra control inputs that come from skid ECU outputs, as seen in this earlier thread. The thing I'll say for sure is that the manuals have some gaps around these details.
Thanks again! Was able to disconnect A58 pin 10. With my luck it decided to snow the whole time but no more possessed hazard lights. The ABS, skid and angry brake light were on initially but cleared themselves after a drive around the block.
Channing or Prof Chapman, I have been all over with same issue and want to try the pin 10 disconnect as I troubleshoot . I have located pin 10. I am not one to cut wires, but would prefer to disconnect. With some mild tugging the pin does not come out and I can tell that the wires are kind of fragile. Is there any particular trick to get wire out of connector?
Expanding on that: most of these Toyota connectors have both: a primary locking lance on each terminal, and a secondary locking mechanism for the entire connector, locking all the terminals in place. When you want to remove a terminal, the secondary locking mechanism is the first thing you deal with. It often looks like a rectangular plastic piece inserted in the connector, with a notch or two where it can be pried up with a small screwdriver. Sometimes it's found on the top or bottom of the connector. With weatherproof connectors, often it's found down inside the connector when you look in the end after unplugging it. Sometimes the secondary lock only needs to be lifted a mm or two to unlock; the ones that are inside the connector between the terminals sometimes get pulled completely out. Once you have the secondary mechanism unlocked, the next step is just to find and squeeze the primary locking lance on the terminal you want to remove, and pull the terminal out while squeezing. The lance is sometimes a metal feature on the terminal that clicks into a notch in the plastic housing, and sometimes it's a plastic feature of the housing and clicks into a notch on the terminal. The details for any given connector are found in the car's wiring diagram. When you look up the right connector (A58 in this case) in the online diagram, you get a page like what you see in this post. Note that post is just an example; it's showing a different connector, not A58. You can see how, for the connector it's showing, the terminal lance is part of the housing, and you lift it by inserting a slim tool from the front of the connector. The details for A58 would be found the same way, pulling it up in the wiring diagram. Toyota Service Information and Where To Find It | PriusChat The wiring diagram has some front sections also, where you may find the dimensions to use for the slim lance-releasing tool. I have released a lot of terminals in my day just using a skinny jeweler screwdriver set and the right amount of cussing, but there was one time I got frustrated enough to actually grab an old cotter pin and grind it down with my Dremel to the exact unlock-tool dimensions shown in the manual, and it did work better. You'll notice the service-information link above also contains a link to an older Toyota "Wire Harness Repair Manual", which is mostly generic information, including basics on how the locking arrangements usually work. It won't have the specific details the car's own wiring diagram has, but it's outside the paywall, so it's an easy thing to review.
Chapman, in your opinion, what is the downside of snipping the blue wire A58? I am going to preplace the hub with the loose speed sensor first then tackle this wire. I replaced the hub a few years back so it should not be rusted into place.
Lol. I will save the cuss words for the wheel bearing and cut high enough to reattach if needed. You think wheel bearing / sensor unrelated? In another matter, i think the parking light went on when my daughter had dimmer turned all the way up to use dome light. I adjusted them off high setting and has not happened since.
Follow up. I cut the blue wire and like magic, blinking stopped. Driven about 60 miles without issue. I still have abs/trac/brake warning lights but those are hopefully due to plug in issue with rear speed sensor. Will tacklethat when temps warm up a bit. Thanks for your help Chap.
