How to fix the U0168 Code on a 2007 Toyota Camry Hybrid?

[yamoffathoo]

I was investigating why the A/C System was not cooling and performed the following test after measuring no connectivity between any of the HP sensor pins, 5V on two of the A21 sensor connector pins and 28 psig at the LP A/C port:

- Turned the A/C switch on with blowers on high and temperature on low
- Connected four 1.5V batteries in series with +ve to terminal 3 and -ve to terminal 1

The A/C blower and indicator lights immediately stopped functioning
The Main and Sub fans both began spinning.
Removed the testing rig and replaced the A21 sensor connector
Powered OFF/ON

No A/C blower or indicator lights
Main and Sub fans both spinning
U0168 Code detected - no others.

My mistake was imposing 6V instead of <5V across the A21 sensor (per attached).
Is there a way of recovering from this error?

 

[yamoffathoo]

I will check the pins for power tomorrow.
I reached out to the local Toyota Dealer for a cost estimate to diagnose the HVAC module (reply attached).

If you are correct about "how could the control module respond over the network with a code that it can't communicate, if it can't communicate?", do you think his suggestion of purchasing a replacement is futile?

 

[BrianPetersen]

I will check the pins for power tomorrow.
I reached out to the local Toyota Dealer for a cost estimate to diagnose the HVAC module (reply attached).

If you are correct about "how could the control module respond over the network with a code that it can't communicate, if it can't communicate?", do you think his suggestion of purchasing a replacement is futile?

What I'm saying is to check that this code is coming from the network gateway, because it is unable to communicate with the control module. I think that's what you will find.

Go into your scan tool and see if you can get any sign of communication with the HVAC module.

There is a high probability that the HVAC module is bad, but you need to rule out unplugged electrical connectors, broken wires (leading to no power or ground to the module), broken network wires, etc. I would say that if you can use your scan tool to communicate with the radio, which is on the same branch of the network, the probability of the fault being within the gateway module is very low.

If a replacement HVAC module is cheaper online than the dealer's diagnostic fee, there's your diagnostic ... but be alert to the possibility that the replacement module has to be VIN-coded to your vehicle before it will work. (Theft protection)

 

[3DDave]

The best part is - if the module is bad now, the module wasn't bad before he started messing with it. Replacing the module with a working module will only get back to whatever the original problem was. Used on eBay they run under $60; from the dealer the price seems to be between $500 and $700, even if it is available.

Getting to the module requires removing most of the dash board on the right side and the center stack with the main user interface car controls. If the skill level that took a few minutes with some wire and batteries caused this module to fail, I expect an hour with prying on other electrical components can get the entire car to be unable to run.

 

[3DDave]

I do like this part of the dealer reply:

The base diagnostic fee for this type of concern is approximately $420.00. However, if the issue turns out to involve wiring or a CAN-bus fault, the work maytransition into straight-time electrical diagnostics, which can exceed $1,600, depending on complexity.

That latter amount is because they typically don't do electrical diagnostics at dealerships. They are in business to replace components and not decide if there is anything wrong with components. They will recommend an entire harness be replaced rather than look for a spot where a harness resting against a sharp metal corner has worn through and either caused a short or allowed salt to corrode the wire after wearing through the insulation.. SMA and Pine Hollow, mentioned above, seem rarely to take as much as an hour for almost all solid fail condition diagnosis, though Pine Hollow has had some that take much longer when the failure is highly intermittent. Oh, and that harness replacement will come only after replacing almost every electrical component tied to the harness.