Hazard Lights Problem Debug Info

Check your 12v battery

 

I have the same problem, and sure would like to know where the Junction Block 3A and 3B is. The manual shows the layout, and I figured anything with that many pins would be easy to find. I have the dash out and don't see anything that looks like it. The manual often refers to checking voltages and/or continuity between pins on it, so it must be fairly easy to get at. Anybody have an idea?

 

Easy for you, if you've already got the dash out! You should see it mounted there on the reinforcement, slightly to the left of the center stack. Doesn't look like much, just a rectangularish box that has the 3A and 3B connectors from the harness plugged into it. It just has internal patterns that connect various of the pins together, as an alternative to a whole lot of wire splices.

You might want to look at this post. The behavior where the hazards flash at a rate that increases with road speed really sounds to me like a short between HZRI and the "speed pulse" signal SP1, which is generated by the brake ECU on the next pin over (and there really isn't anything else it sounds like that I can think of).

There's also another member currently looking at a (different, but) possibly related situation.

 

Thanks. According to the wiring diagram there are three inputs to the flasher module that are joined together at the junction block. I figure that is the best place to figure out where the ground is coming from. Here is a picture. Is it in the box under the green and orange cables? Nothing looks like the diagram in the manual. The dash actually came out pretty easy. Having done it once, I could probably do it again in 10-15 minutes.

 

Looks like you've only removed the upper dash, lazybones.

The box you're looking at there is the power steering ECU. If it were gone you might see a bit more of the JB No. 3 in the photo. It's a bit to the right, closer to the midline of the car. It is mounted to the reinforcement (that big round metal pipe thing).

I remember spotting it when I had my dash off, but I didn't take photos, sorry.

Because the usual symptoms give a clear suggestion of where the grounding is happening, if it ever happened to me I think HZRI / SP1 is where I would focus first. In the diagram, of course, JB No. 3 makes a perfectly logical place to divide and conquer the problem, but in physical layout, as you see, it's not convenient.

Edit: was sure I had to have this diagram somewhere. As you can see, when you're looking at the steering ECU, you're getting pretty warm.



It turns out when you download from the online wiring diagram manual, this diagram ends up in the PDF for engine compartment relay locations, which is why I thought I was losing it for a minute there.

Looking things up is really easier when you're signed in to the online diagram, and then you just highlight circuits with the mouse and click Info and boom, you see where all the bits are.

 

Thanks! You've really been a big help. I agree that the logical cause of the trouble is in the ABS unit, but I thought that the junction blocks would be easier to access. The service manual refers to taking measurements from the 3A and 3B junction blocks in most of the trouble shooting steps for most of the various circuits in the car.. I figured Toyota had placed them where they would be convenient for their techs. Wrong again.

My diagram shows your junction blocks as CAN J/B 3 and 4, and they appear to be way smaller than J/B 3A and 3B should be, having 84 and 96 pins each. Hope you can see why I was confused. And I can't even find anything in those areas that resemble the diagram in the manual. It is such a simple circuit that I figured this would be easy. It would be if I could find anything. [Sigh] There is just too much I don't know about this.....

The resistance to ground at pin 8 of the flasher is supposed to be >10k, and it shows 280k, so I suspect the short in the ABS must be internal and active. Not looking forward to figuring out how to get to that to check it.

Thanks again for all your help!

George

 

The problem certainly is originating inside the ABS unit. I fixed it by adding an air gap to the wire. Now everything is working except my flashers will no longer flash when I am skidding. (That has never yet happened.)

 

hi there like a few others i to am having this issue ,,, can you advise please which wire you cut to stop the signal being sent to the flasher unit if skidding, lets face i your brake lights will be on anyways, ??

 

Pin 4 of junction block 3B. But I would not do that again. Spice a new wire from the yellow wire on the flasher switch to pin 8 of the flasher unit. Means the flashers won't flash when you unlock the car or hit the panic switch on the fob, but it will save you an hour or more of work getting to the j/b. A complete description is on this forum.

 

clean the ecu connector under the hood and change the hazards relay which is under the steering then it will be fixed.

 

That may have worked for someone for some reason, but as a recommendation that'll be dubious unless someone pins down what was at fault and how, and can make that explanation fit with the already-gathered evidence.

It is true that the HZRI and SP1 pins are right next to each other at the brake ECU connector,



However, when a member with the problem investigated, the connector and terminals were pristine inside.

That would be the thread to continue on with further exploration. As far as I know, no one has yet obtained a unit with the problem and disassembled it for further exploration inside. That would be a sensible next step.