2005 prius throwing code p1121 is this the 3 way valve or throttle position sensor?

Have you checked the repair manual yet?

Sometimes there are a lot of conflicting things said about what a code does or doesn't mean, if you're just looking through search results. The reports that match what you find in the manual are generally the correct ones.

 

techinfo.toyota.com is the authoritative source.

Apparently there are also services often available through public libraries that include some or all of the content from the real manuals; I'm not very familiar with those alternatives but you can find lots of posts by Elektroingenieur giving the details on those.

There are sometimes people on PC who have downloaded the manuals and will share some portion of them, ranging from a particular figure or page obviously connected to a question in the forum (which I'm pretty sure could be defended as "fair use"), to maybe an entire section, to putting the whole thing on file share (which I'm pretty sure would be harder to defend if challenged); different people make different judgment calls on that.

From what I can see, the detection conditions for P1121 are (one of): no change in the coolant valve position sensor voltage despite the ECM sending a valve control signal (or a too slow rate of change); the thermos outlet temperature sensor reading too high when recovery is just starting; or the outlet temperature reading not changing over the course of recovery.

Nothing in that at all about throttle pedal, which suggests that whatever data somebody has entered into Torque Pro doesn't really count as a good substitute for the manuals.

There are about four pages of troubleshooting techniques given for that code.

 

Here is the workup for DTC P1121 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/repair%20manual/04pruisr/05/2054m/cip1121a.pdf

 

A failed three way valve has no significant impact on the engine or drivetrain. Its purpose is to switch the flow of hot engine coolant between the coolant heat recovery system canister and the cabin heater core.

The canister stores ~3 liters of hot engine coolant in an insulated thermos type container, and this coolant is used to speed up engine warmup upon the next engine start.

The factory repair manual provides instructions on how to test the valve by using Toyota Techstream to move the valve to the three possible positions, then to measure voltage between two pins at the engine ECU to see what voltage is reported. That voltage signal is the way the ECU determines if the valve has moved to the correct position.

 

I added a Toyota Service Information and Where to Find It page to the PriusChat Wiki several months ago, so I could just add a link there when writing about the manuals, rather than explaining every time.

 

There is a slight possibility of the hoses being crossed during the install (its happened before), and I've also read that the canister temp sensor can fail (fairly rare).

How are you reading these codes, and which DTCs were most recently thrown ?

 

The engine coolant loop is separate from the inverter/transaxle coolant loop. Hence a problem with the engine coolant valve would not have any impact on the inverter or motor generator temps.

 

The motivation for the CHRS system is to reduce cold engine exhaust emissions. Each Prius engine generation had some strange emissions-related system:

Classic had the bladder fuel tank and HCAC (hydrocarbon absorption chamber) upstream from the catalytic converter. The valve controlling exhaust gas flow to that tends to bind up and stick, and of course the replacement cost of the exhaust system is into four-figures.

2G had the bladder fuel tank and the CHRS system. That enabled the Prius to qualify for the CA AT-PZEV emissions rating. At the time, that enabled the Prius owners in CA to get carpool stickers allowing solo use of carpool lanes. That rating also required Toyota to offer extended warranty durations on the traction battery and certain other drivetrain systems in CA (and those states following CA emissions control regulations).

3G got rid of the bladder and CHRS, but instead has an EGR system which has proven to be a real pain, if you review the 3G discussion boards here. Clogging of that system can cause engine misfire and even cylinder head gasket failure. These issues are much worse than the 2G three way coolant valve failure which turns on the check engine light but has no noticeable impact on engine performance.

 

If it helps the European version of the Prius does not have that tank.

 

I bought this for and with the App I can track data from all of the Prius sensors. It’s like having tech stream running all the time. I can tell before something happens. No more stupid “multifunction” lamp for me.



iPhone ?

 

You May be on to something. I’ve had /02 sensor issues for years. This may be why.


iPhone ?