B1497 - Communication Malfunction (Bus IC) - need help

Wasn't sure if I should start a new thread as there are lots of related posts here in Priuschat. But I've also seen replies in those thread saying to start another thread as they are old and will not be seen. So mods let me know or just merge with other thread and i'm ok with it.

Anyway, i have had B1497 since winter but since it was stuck in heater position I postponed opening until summer. Finally opened the dash this week and sure enough all my all dampers/flaps (air inlet, air outlet, air mix) are stuck in 1 position. From the internet I found Toyota lists 2 causes:

B1497 BUS IC Communication Malfunction
1. Air conditioning harness
2. A/C amplifier

I checked all the fuses under the dash and in the engine bay, except the fuse inside the inverter and the connector to the compressor as the AC is working. As cold air blows until the engine warms, then the heat overcomes the cold. But the AC keeps on working and continuously blows ice cold air anyway, so obviously only the dampers are in the wrong positions

I disconnected the Air mix servo, disassembled the unit, and tested the motor with a 9v battery (just to eliminate the possibility) and sure enough the motor is working, all gear teeth intact and turning. So those are out of the way.

So here is where I need help, because my electrical knowledge is limited to testing fuses only LOL! The harness seems the next cheaper/easier to test. Google says one way to check is by sticking the positive of a multimeter into the harness and the negative into the car body. So...

I tried sticking wire clips into the connector like this and testing with the multimeter and got nothing

But I wasn't also sure if the pin connected well, or I stuck into the wrong holes.
So I disassembled the servo motor, identified the positive...

and connected them to the harness so I was surer I had the positive terminal. So far I got nothing.



So my question is, was my test good enough to conclude I need to replace the harness? Or did I need to have the car running to run the test? (LOL!...like I said, my electrical knowledge is quite limited).

Any help would be appreciated. Thanks!

 

Wow, thanks Chapman. That explains why i saw the same wires connected to all 3 servos. Unfortunately i just changed my front brake pads and lubed all my brake pins (more than 2 hours disconnected batteries). So that battery reset trick is not going to work for me like the Prius C mentioned from your link.

Hmm....I think it's time to get the amplifier tomorrow, see if i can pry it open (if possible) and eyeball anything burnt. Worse case i will just have to buy some used cheap amplifier.

 

I agree... i'm just waiting for the amplifier I got from ebay. At only US$25 plus $16 delivery it was still cheaper than a new harness at US$82. The open dash was a non factor. I had that open in about 25 minutes, and could probably snap it back in 5.

Something curious though after I made my order. I went back to the car and tried with the harness disconnected, and the codes didn't change. Since that didn't really prove anything (as the problem could still be the harness or the portion of the ampli circuit dealing with the harness), I tried with the ampli disconnected and something ran inside the engine bay which sounded like the compressor or the radiator fan. I didn't really take time to confirm tho as I switched off quickly. I was so shocked i wasn't even sure if I switched in accessory power mode only, or i actually stepped on the brakes and that thing ran instantly before the engine could start. I don't think that observation helps in my situation, but for a noob I just found that strange.

Anyway, I will update once I get the part sometime around the 20th. Thanks

 

Hi Tia. Sorry, replacing the amplifier nor replacing the harness didn't work for me. I'm guessing my problem goes much deeper. Maybe the communication bus, or worse. I suspect someone tried to boost my car while I was not around, and fried some electronics.
Since this was getting beyond my noob abilities and I probably will be replacing within 2 years I gave up. I now simply open or close the dampers manually during fall and spring. I figure in the 2 years I have it, I only need to do that 4 times lol. But your case may be different so don't give up yet.

The amplifier is just a couple of inches above the floor, to the right to the gas pedal (for left side drivers). It is held up by a single screw and is very easy to disconnect/replace. I'll see if i can post a picture of it later.

For the lower actuator, you don't need to remove the dash. Just the glove compartment and some flimsy plastic in the foot well. There are threads here in Priuschat showing how to do it.

The 2 upper ones does though, so I'll post my DIY files if I can find it. Stay tuned lol.

 

I pulled out the amplifier (don't worry, I never screwed it back so it was easy) and laid it over the gas pedal. It's quite dark in my garage, so I had to over expose:

 

This is someones vid i followed to remove the dash (this is only if you want to replace the harness, or access the upper servos). I took screen shots and made a quick guide for myself which is why it went quickly for me. But Priuschat complains it is too large to upload. So just watch this a couple of times and you'll be ok.

 

Yes, the lowest flaps control the heat...you need to push those flaps open. You can reach those by removing the white air duct that bends down to direct heat to your feet. But you also need to detach the servo motor shown in your pics to disengage the gears. It's a bit tight tho, but there is a thread here in priuschat that describes how they removed the servo and the air duct.

The top flaps control the upper air vents. If your getting air from them, you should be ok. Otherwise the entire dash has to come off. I just jambed a piece of wood to keep mine open for now.

I kinda remember having similar readings. So I'm guessing those are the default values. I also tried to change the target values via tech stream and the actual values never changed. Since the harness I got was brand new, the amp is probably the problem (or the control unit which I haven't replaced like you). I did pry open the amp but could not detect any burnt parts. I also don't know how to test it either.

But if you can find another prius and test by swapping amps, you might not have to do all of these. I highly doubt it's the harness.

 

Yes that's one.

 

I found my old HVAC diagram.

I think I may have been mixing the 2 flaps. I did do both the top and the bottom the same day and is why I am getting confused.

Do try waiting until your engine is fully warm before opening your dash as i kinda remember playing with the lower flaps and getting hot or cold air, before opening up the upper flaps. It could save you all the effort to make sure.