Prius error code P1122

Are you using Techstream to retrieve the codes?

You are .8gallon short! The two times I have done a drain and fill on the engine cooling loop, inverter cooling loop, and topping off the respective overflow reservoirs, I used (~3gal): 2gal engine loop, .8gal Inverter loop.

1) There is air in the engine loop.
2) Did you check inside the radiator?
3) How did you bleed the engine and inverter loop?
4) READ Post #16 and #19, click the links w/in the respective posts and take notes. Inverter coolant and engine coolant flowing through the same radiator? | PriusChat

Search again.

 

Get Techstream since you DIY.

Techstream is the OFFICIAL diagnostic and maintenance software made for Toyota/Lexus, and used at Toyota/Lexus dealerships. Bluetooth OBD2 readers and all the various apps for smartphones/tablets are convenient (small and portable) but junk: LIMITED code reading ability (can't read ALL codes) and can NOT do any maintenance (bleed brakes, engine compression check, activate CHRS pump, etc). Why waste money on a toy that limits what you can read and can't do maintenance?

Get mini VCI w/ Techstream from Amazon ($18+). Doesn't matter who you buy from, as the cables likely come from the same one or two suppliers from panda land. May have to return/buy a few, as some cables have problems (bent pins-easy to fix to dead cable-return). Installation easiest on a Windows 32bit OS (XP, Vista, 7). Ask friends/family if they know someone in IT; this person will likely have obsolete laptops laying around, and might be able to donate for free. B/C the software is hacked, recommended to install on a spare laptop; do not use this laptop for sensitive information (log in & passwords: email, bill payments, etc). This laptop is now your Toyota/Lexus diagnostic laptop. Mac install possible, you just need to search online.

Should you stop driving a Toyota/Lexus, you can easily sell your Techstream laptop set-up here. Private Sales | PriusChat​

Research better. BETTER YET, get the factory service manual or Bently service manual. You can always use your library card to access the Chilton manuals online, but the quality of info may be lacking.

For the official Toyota service/repair manuals (engine, mechanical, interior, exterior, electrical, essentially EVERYTHING), go to TIS
Two days will cost you $20. Supposedly only business days are counted . If you start on a Friday 12:00:00 AM, you have until Monday 11:59:59 PM, to finish. You can read this persons TIS visit and download adventure. Toyota TIS download tips | PriusChat

The drain&fill schedule for the engine and inverter coolant is 10years/100,000miles, whichever comes first (years or miles). Then after that every 5years/50,000miles. The protective chemical properties of the coolant wear out over time. Toyota has determined the drain/fill schedule above to protect, yet minimize the frequency of coolant change. Your 2004 should have had at least two drain&fill events: Initial in 2014 (10yr/100k miles). Then another one in 2019 (5yr/50k miles). If the car has far more miles, then it would have far more coolant drain & fill events.

No.

So, you checked that the voltage and resistance were w/in factor specification for the valve and ECM (Electronic Control Module), to determine whether the valve or ECM (Electronic Control Module) or both were bad?

Thus the problems of reading posts and watching YouTube: accuracy of info. Factory Service manual would solve that.

Spend just a little bit more time reading. Same screenshot as above. Your ANSWER was always there; see RED CIRCLED BOX below.
Should you choose to read that PDF (which "appears" to be from the factory service manual), it provides the trouble shooting steps for DTC P1122, the specs for voltage and resistance, and which connector and pins to test, to determine which part/s (valve, ECM, or both) is/are bad.
Search words "toyota dtc p1122"

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The factory service manual does WONDERS!

YouTube can be useful. But the accuracy of the information is NOT always there. Great for entertainment and to get an idea of how involved a procedure might be. BEST to always reference the factory service manual: its the authoritative bible for your Prius.

 

I would drain and fill the engine loop after you determine if the ECM, 3-way coolant control valve, or BOTH, need to be replaced. If the 3-way coolant control valve needs replacing, makes sense to do a proper drain and fill. Now both inverter and engine loop will be on the same schedule.

Last time I bought Toytoa SLLC, it was $16.95 at a local dealership (Apr 2018).

Did you buy a Toyota OEM 3-way valve or was this an aftermarket (Dorman, etc)? I do not recall any posts where the ECM for the 3-way coolant control valve needed to be replaced. I do recall aftermarket valves not lasting long at all. If you installed an aftermarket valve, I would put money that the aftermarket valve is the source of the error; replace w/ an OEM 3-way valve.

 

You are using a "good" DVM? It doesn't have to be an electricians level DVM (costing $100s), but definetley not Harbor Freight (esp the free one). A $30-$60 one, good brand name, on sale should be adequate for most DIY repairs.

Don't forget to account for the resistance your "rig" will likely introduce, possibly giving a higher reading.

DTC U0100 = lost communication w/ ECM/PCM "A"
Interesting. This code NEVER appeared until now? But the code makes sense. Before removal they were talking. Unplug, it lost communication (U0100). Would makes sense that you are seeing the code now, after plugging in, to let you know, hey, there might be a problem; but you know the cause of this "problem," as you triggered it by disconnecting to trouble shoot. I would clear all codes and proceed.

I highly doubt the ECM would require reprogramming. Why? Could you imagine how pissed owners would be to have the car reprogrammed every time the 12V died? Disconnecting the cables (as you have done) would be the equivalent of a dead or removed 12V battery; real world. Having to redo the clock and radio presets is a near universal inconvenience/pain.

A bad 3-way coolant control valve only triggers a CEL. The CEL can be intermittent as many people experience; the valve might be able to get into the correct position, deactivating the CEL. A dead/stuck valve would cause the CEL to stay on, until it is replaced or able to move into the correct position. Oh, I have learned here that the CEL is Emissions Related. The other warning lights will be for other systems.

The Master Warning light, VSC, !
will have codes, unless you cleared codes. If the problem still exists that caused those warning lights to trigger initially, the warning lights will appear again. Thus the importance of having proper tools (Techstream). Universal/generic OBD2 readers can NOT read all Toyota codes. If those warning lights get triggered again, you will have to have the codes read at the dealer or a shop that specializes in Prius and will likely be using Techstream or another professional commercial code reader that can read all Prius codes.

Do yourself a favor and get Techstream since you DIY. Should you stop driving a Toyota/Lexus, you can sell your Techstream setup.

 

P3009 is a HV leak. Hopefully it is limited to the HV Battery, and not the transaxle.
Should you ever get Techstream, P3009 has subcodes that further pinpoint the likely problem areas.

New = assembled from 100% virgin components/materials.
Was that battery a NEW OEM HV Battery from Toyota? Or is it "new," as in a euphemism for used/rebuit/reconditioned/remanufactured/etc?
If it is a euphemism for "new," don't count on the HV Battery being trouble free or lasting a long time. Start planning a repair/replacement strategy.