HVAC Issues and Diagnostic Codes

Hello, First Post. Thanks in advance to all those that contribute. I have noticed a couple similar past threads that never came to a resolution...

2017 Prius 4 Touring.

I'll first summarize my findings: I have run the in-dash HVAC diagnostic and it gives codes 41 and 48. Only heat blows when the engine is on regardless of temperature setting. Hot/Cold blend damper/actuator assumed in operable. Passenger/Driver vent damper also not operating with no air coming from passenger vents. Can someone summarize the trouble codes? Can anyone tell me what the damper "clean" function is with service software? I did try disconnecting the battery for an hour and that did not reset it.

Explanation: This weekend I noticed the A/C was off when I got in the car. I'm in coastal virginia and warm enough to use the A/C. The A/C was on before exiting on the previous drive so I immediately thought it turning off was strange. After turning it on, it worked normally until the engine warmed up and then would only blow hot air. I got home and noticed the correlation between the engine running, warm air from heater core overwhelms the AC. When the engine turns off and the latent heater core heat is removed the air becomes cold again. When the engine is off I can hear the A/C compressor running. I'm not certain if the compressor is running with the engine running. I didn't need the self test to tell me there is certainly an issue with the air blend damper. Normally, I would just research how to replace it and not have any questions for this forum.

However, there is also no air coming from the passenger side upper vents regardless if eco/normal is selected or there is a passenger in the seat. The display indicates that air is flowing to the passenger side when normal mode is selected. That leads me to suspect that the driver/passenger damper is also stuck. I find it very strange that two separate actuators are not working. That said, I'm not certain when the driver/passenger damper quit working. It could have quit working weeks ago.

I researched the self diagnostic process and as I said it returns codes 41 and 48. It seems that code 41 is the blend damper. I assume that 48 is the driver/passenger damper.

So I started researching the repair options. It seems that the appropriate software can diagnose and test the actuators in question. Can anyone confirm? It also seems that there is a "clean or reset" feature with the software. I have no experience with Techstream or any diagnostic software beyond the most basic scan tools.
I've just started to research getting techstream and a cable.

Thanks for reading; any advice is appreciated.

 

Yes, the HVAC trouble codes are accessed with ignition on and auto/recirc buttons held. Same as previous generations.

I fixed the problem. It did require replacement of the air mix servo assembly (Servo Sub-Assembly No 2, SSA2). Long story short, entire dash has to be removed but I was able to replace it without removing the entire HVAC assembly as is instructed in the Toyota Repair manual. Story as follows:

I ended up getting a OBD/USB cord and a copy of techstream from the interwebs. My hope was that I could simply "initialize" the servo motor. That did not work. I ran tech stream and it also returned codes P1441 and P1448. I purchased the 48 hour access to TIS (toyota factory repair manual). If my memory is correct, the trouble shooting flow chart indicated that code 1448 or 1441 alone indicates a bad SSA2. It could also be a mechanical issue such as a linkage is jammed or broken. A combination of codes1441, 1447, and 1448 indicated it could be the SSA2 or the AC Amplifier. The factory service manual says removal of the SSA2 requires the entire HVAC assembly be removed from the car. It's a huge job. Remove the dash and steering wheel, remove some structural frame components under dash, disconnect the refrigerant and coolant lines, remove the wipers; I'm sure you get the idea that it's terrible. I downloaded every removal and assembly document of TIS that seemed applicable. It was at least 30 individual documents as the removal process has several internal references that branch out. It's a bit of a pain. Also, as I mentioned at the top, I didn't use many of them.

I bought all the AC servos and an amplifier as a package off ebay for a couple hundred bucks. The SSA2 actually has three servos on it. The recirculation servo, the passenger flow servo, and the air mix servo. It was tough to cross reference the part numbers so I made sure it came from a 2017 4 Touring. My understanding is the AC amplifiers are different because the touring incorporates seat warmers that other models don't have. To my knowledge if you don't' get the right amplifier, your seat warmers may not work. Not 100% on that.

So, I now had all the possible replacement components. After you remove the glove box you have pretty good access to the SSA2. However, you cannot remove it. It has three philips screws that hold it in place. One is relatively easily accessible. The other two are not. The SSA2 is sandwiched between the main HVAC assembly and the blower assembly. There is only about 1.25" between the two and you cannot get a standard phillips head screwdriver on the screws. Also one of the screws is on the top of the assembly and you have no line of sight to it from the bottom. However you can unplug the Air Mix servo from the bottom. I did that and plugged my replacement in it's place. I reinitialized through Techstream and 1441 went away but 1448 stayed. Basically, the computer saw that the Passenger Servo was not moving but it recognize the the Air mix servo was now moving. You can go into techstream and manually send signal to manipulate these servos and the computer will show if it in fact did move. I later learned that the SSA2 has to be installed in order for the computer to recognize the movement passenger actuator.

Unlike the Air Mix servo, the AC amplifier is relatively easy replace so I decided to replace that next with the hopes that it would turn 1448 off. It is located to the right of the accelerator pedal assembly mounted on the backside of the HVAC assembly. Above the "transmission tunnel" if you will. You can't really see it but you can see the plug on the bottom. It's has one hex screw holding it in place. I replaced it and it did not fix anything else. Damn.

That evening I realized that I may need to actually replace and install the replacement SSA2. The next day I started removing the dash with the hopes that once it was out I could get a better look at the hardware. It's not too difficult to remove the dash but it is time consuming. I took plenty of photos and videos of what I was doing and labeled everything as I went. There are a few youtube videos that depict the top dash screen removal and main screen. I couldn't find a video for the full dash removal. The rest of the removal instruction came from the printouts I made from TIS. I should mention that I had to remove some SRS components so be sure to disconnect the battery. TIS instruction states that you need to remove the seats and center console assembly to remove the dash. I also found that was unnecessary. Once the main dash cover was removed, I could get an idea of what I was up against. I also had to remove a section of duct/damper that was on the top and center of the HVAC assembly. It was part of the windshield defrost manifold. It was black. Once it was out I could see the other two phillips screws that held the SSA2 in. You cannot remove them with any type of standard phillips screw driver. I do have some 3/8" square drive bits that could put on a ratchet and those were also too long. I ended up taking a phillips bit for my cordless impact driver and cutting it with a grinding wheel so that it was about a 1/2" long. I superglued that into a 1/4" box end of a combination wrench. I painstakingly used that to turn the two screws out a 1/4 turn at a time. It took me at least a 15 minutes each to get them out. Once they were out, I could pretty easily pop in the replacement SSA2 once all the servos were aligned. I painstakingly put the three screws back in to mount it. I knew that I could not test it until it was all back together since at least 30 plugs were disconnected including 4 airbags. Basically, put it all back together, reinitialized,cleared codes, and it was fixed. It took me about 8 hours altogether working at a deliberate pace. One funny thing did happen. I forgot to plug in the fuel door release switch. 5 days later I got to a gas station and the door would not open. I knew immediately what the problem was. I tried to gently pry it open but it seemed too risky. Fortunately, I still had most of my tools in the trunk and I was able to get it plugged back in in about 3 minutes. Otherwise, all is back to normal with no issues.

 

I'm not sure, I never got a quote. I was expecting $3-4K. The servo assembly was $500 alone. I expect they would have "charged by the book" regardless if that's what they did. That meant removing everything else you see in the photograph and would require evacuating and recharging the AC system.