I was troubleshooting a P2601 DTC on my rebuilt (salvage purchased) Prius. I had previously fixed all the known DTCs, got the vehicle inspected and was driving it for 1 month (July) before this DTC appeared. After it first appeared, the DTC would always reappear. I had been busy with other things, and didn't get to spend enough time with it. Friday I had the day off from work, so I checked the fuse, and then the CHS relay. The relay was missing! (as was the PTC relays). I cannot figure out how the car ran without a DTC if the relay was missing since I acquired the vehicle, nor can I figure out when someone could have removed it after I got the car to pass NY inspection. At any rate, I went to purchase replacement relays, and first was told it was a dealer only item. I did some more research, and found in fact, it is available from Beck/Arnley part # 203-0133, and my local auto parts store was able to get it for me the same day for $6.99 each, which is a fraction of the $25.49 Toyota list price. It is also available from Rock Auto, but the shipping makes the price much higher, unless you need to purchase other items also. So far, the relay is working fine, and as an electrical engineer, $7 is the right price for this type of relay. If anyone has any theories as to why the DTC did not appear for so long, I would love to hear it.
It's good to hear about your aftermarket relay source. I once had to pay ~$75 to have the circuit opening relay on my 2001 replaced as part of implementing a TSB. I subsequently determined that the original relay was fine and reinstalled it before selling the car. I've kept the newer relay (with sky-blue colored case) in the glove compartment of my 2004. My theory about the delayed appearance of the DTC is that the engine ECU memory was filled up with the other trouble codes. It took one month for the codes to be purged out so that there was room for DTC P2601 to be logged. So now that you've installed the CHS relay, do you find that the coolant heat recovery system works OK? Do you hear the pump running when you first start the car in the morning, and also hear it when you make the car IG-OFF?
Looking at the description of P2601 in the manual, it lists Typical Enabling Conditions (i.e. when the monitor will run). It appears that the monitor will only run when no Coolant Heat Storage system malfunctions are detected. If the system wasn't working, then it doesn't run that test (but it should log a different code).
Patrick: I cleared all the codes, and the CEL was off for a month. Not only that, NY state inspection checks that the car reports it was driven through at least 3 driving cycles, and that at least 50 miles have been driven before the inspection will pass. The car seemed to think all systems are running fine. And yes, I now hear the pump when I turn the car off. You need to be aware of the different sounds though, because even if the pump is not running, it makes other sounds when it turns off. The car is still running OK since Friday, so all is well now anyway
