05 Coolant Pump Operation Questions

Hey Greg, long time no hear from. Lets see if I can't figure this out.

Question 1; Yes it only runs at start up and shut down. It also may start up approximately 5 hours after shut down to check the coolant storage system.

Question 2; I doubt the relay contacts are welded shut. The relay has constant 12 volts to it even when you go to Ready Off mode ( shut down ). This is because of when the ECM turns the pump back on after 5 hours ( see above ). If the relay contacts were stuck, you would have the pump running 24/7 and that would not be good.

Question 3; If both hoses are cold, yes you have an air pocket in the system. This could explain the pump running because the temp sensor in the bottle is telling the ECM that the coolant bottle is not at operating temp. I am not sure if the pump will stay running in this state because I have never run into that before. When changing coolant on the 2nd gen Prius, I always have our Techstream ( our new diagnostic tester/laptop ) hooked up and monitor both the Engine Temp and the Coolant Bottle Temp. This way I know when the bottle is full of hot coolant; both temps will be the same.

So you really need to get back to the dealer for them to fix the problem. Knowing the trouble code should lead them to the problem, but also the coolant level should be double checked and any air in the system bled out. There is a procedure in the repair manual for changing the coolant and you can't short cut it or air is the result.

Hope this helps out. I still check my email at least once a week or more so don't hestitate to PM me if you have more concerns. I may not visit here as much as I used to ( my how time changes as you get older ) but I still like to help Prius owners out when I can. Just ask the ones I help at my dealership. If I don't know the answer right then, I know where to get it, .

 

Just found this post after searching for help with my Prius problem. I'm getting DTC P2601 every time the car tries to use the coolant heat storage pump (i.e. at startup when the engine is cold). The heat storage tank is always cold as well as all the hoses connected to it. The cylinder of the pump near the connector is hot, but I can't hear the pump operating when it should be. Could the pump (Toyota part number 16290-21010) be fried inside? The heat storage tank was recently replaced, but I don't think the pump was. I have tried to bleed all the air from the radiator coolant with the bleeder valve, but I don't think that is the problem.

 

DTC P2601 "Coolant Pump Control Circuit Range/Performance". This DTC is triggered when the difference between the temp from the coolant tank outlet vs. the engine coolant temp before and after preheating is under 2 degrees C; or when the coolant tank outlet temp is within 1 degree C vs. the temp before the pump runs in soak mode.

The likely reasons for the DTC include the coolant heat recovery pump, the associated relay, a wiring harness problem, or the engine ECU.

To test the pump and the associated wiring harness, I suggest that you locate the CHRS relay located in the relay box mounted to the cowl, when the car is IG-OFF. Remove the relay and use an ohmmeter to determine the relay coil terminals and the switched terminals (one pair is copper colored while the other pair is silver colored.) The coil terminals will show ~100 ohms resistance while there will be infinite resistance across the switched terminals.

Once you have identified the switched terminals, find the relay socket terminals that correspond, and use a paper clip to bridge those terminals. This will force the pump to run.

If the pump doesn't run then you know that either the pump is bad or the wiring harness between the pump and the relay is bad.

If the pump runs, then apply 12VDC to the coil terminals of the relay, and measure the resistance of the switched terminals. The resistance should be 0.5 ohm or less. If higher, then replace the relay.

If the pump, the relay, and the wiring harness are all OK, then the engine ECU, the wiring harness leading to that ECU, or the temp sensor is the problem.

What was the reason for the coolant tank to be replaced? Did it just fail; or was this due to an accident?

 

Thanks for the quick reply. I recently bought this Prius as a rebuilt/salvage title, with front end collision repair (radiator, headlights, CHS tank, bumper, etc) and have gotten the P2601 code from day 1. At least it's not critical to the car's operation (only to help warm the engine/reduce emissions), but it's annoying to have the same check engine light code come on every day.

I checked the operation of the CHS pump with a 10A fuse across the relay socket terminals (copper prongs), and there is no sound or coolant flow near the pump. The only thing that happens is the pump itself gets hot. I figure the pump is fried inside, or could a complete blockage of the hoses cause this?

 

I agree it is likely that the pump motor is dead. If you want to be sure, you could remove the pump from the car, then apply 12VDC power to it and see if the motor starts to spin. Good luck.

 

Hi Rick,

Is the procedure for changing the inverter coolant impossible to do for a DIY as myself? I typically do most work on my autos and only bring to the dealer when I do not have the specialized tools needed for the job (such as alignments). It's not that I distrust the mechs at the dealers but I find it much more convenient to do work myself if possible.

If I could do it myself could you post the instructions from the manual on how to change the fluid properly? I am at 78,000 miles on a 2006 and know the change is due at 100,000.

Rick
#4 2006

 

Here's the procedure from the Totota Repair Manual, section CO (cooling). See pages 6-9. Bleeding the air from the coolant takes a while.

 

Hi Rick (aka viking31),

The procedure provided by maseace is for the engine coolant system. I agree that this procedure is relatively time-consuming due to the need to fill the coolant heat recovery canister (I suggest using my relay bypass technique mentioned above to power the CHRS pump when initially filling the system.)


However, since you asked about the inverter coolant in post #8, please note that drain/refill for this is relatively much easier than the engine coolant. You may wish to download the relevant pages from techinfo.toyota.com; however I have summarized the procedure below and added a couple of helpful hints of my own:

• Make the car IG-ON (not READY). This is where all the instrument panel warning lights are on.
• Listen to the sound of the pump running; you should not hear any air bubbling in the system. Also note that the fluid level at the very back of the reservoir tank mounted to the inverter is higher compared to the fluid level throughout the remainder of the reservoir tank. Commit the sound of the pump and the sight of the fluid level to memory.
• Make the car IG-OFF.
• Remove the black plastic shield over the radiator; six plastic fasteners hold it in place. Use small Phillips screwdriver to twist each fastener while applying upwards pressure on the shield near the fastener, to pop the fastener up.
• Drain the coolant by removing the drain plug at the bottom of the transaxle (need 24 mm or 15/16" socket)
• Note the amount of drained coolant
• Replace and torque drain plug with new aluminum washer to 29 ft.-lb
• Loosen the bleed valve in front of the inverter. The manual suggests attaching a clear vinyl hose between the bleed valve and the opening on top of the reservoir mounted to the side of the inverter. However this is not necessary if you don't have a hose of the proper inner diameter.
• Fill the reservoir with Toyota Super Long Life Coolant. When you see fluid coming out of the bleed valve, close the valve.
• Make the car IG-ON (not READY) for 20 seconds.
• Make the car IG-OFF.
• Loosen the bleed valve to let air out. If only fluid comes out, then this is good. Tighten the bleed valve when you are done.
• Fill the reservoir as needed; repeat making the car IG-ON to run the pump, then IG-OFF, then bleeding air out of the bleed valve, etc.
• Listen to the sound of the pump and look at the level in the reservoir. Keep at it until you do not hear air in the system and you see the step at the rear of the reservoir.
• Leave the car IG-ON for 5 minutes after you think you are done. Hopefully you've used at least as much new coolant as the old coolant that was drained.
• At the end of that time, if you still do not hear any air in the system and you still have the step at the rear of the reservoir, then you can declare victory.
• Make the car IG-OFF and top off the reservoir to the Full mark. Securely tighten the reservoir cover.
• Replace the black plastic cover over the radiator.
• Take the car for a test drive to make sure no warning lights come on.
• Check the reservoir level for a few days when the car is cold, top off if needed.

 

all i can say about jumping the terminals to manually run the chs water pump is that i really hope that coolant flow control valve being closed off in ig-off doesn't cause a problem in the long run.

just want that to be out there so people are informed.

 

Hi Galaxee,

Thanks for your concern. I'm not sure that the valve in fact is closed, as per our previous discussion on that subject. If you can suggest a better approach for a DIYer who does not have access to the Toyota laptop or hand held tester, please let us know!

In any event, a typical owner will have SLLC engine coolant replaced at 80K to 100K miles, then at 50K mile intervals. How long will the average Prius remain in service: 200K miles?

So a DIYer only has to change coolant 3x at most, before the car heads to the junkyard. Hopefully the CHRS water pump and flow control valve can withstand manual operation 3x.

 

per our previous discussion, evidence indicates the valve closes once the hot coolant is in the tank and the pump shuts off. the two pages that we both brought to the discussion aren't contradictory, but different points on a timeline. nobody knows the long term results of pumping against that closed valve, and the valve cannot be manually controlled like the pump. in addition to the pump and valve, the tank is involved here too. what happens when you pump successfully into a well-sealed system? i tend to think of pressure accumulating- in a low pressure coolant system. it could be that the tank is the reason why you can't use a common vacuum tool to bleed the engine coolant and do the job in no time at all.

i just think that disclaimer should be known. mechanical parts do tend to do things we don't like when they're stressed certain ways they may not be made to deal with. you stated in your original report that triggering the pump did not appear to be all that useful itself, so i just don't understand your analysis of the benefit being greater than the risk.

i'm really not trying to discredit you- based on the evidence you found, it is a very clever idea. when further evidence comes up, it's time to take a second look. that's science, i do that often.

i wish we could be as involved in the prius community as we have been for the past few years, but we've made a lot of sacrifices lately. my hands are tied on the how-to tutorials for quite some time.

 

Looks like Pearl will be needing a new coolant transfer pump soon. She makes a lot of noise at startup and shutdown (strange intermittent squealing with "thonks" interspaced), which just started last week. Still pumps I guess, but it's getting worse day by day. I presume it will be warranty.

Was there a bad batch of pumps or something? This one's only just over a year old.

 

The challenge of DIYing a coolant change still seems daunting, and I've done a partial change already. I did make use of a Mity-vac, which helped remove air from the system, but the valve positions seem a bit much to handle without appropriate equipment. I suspect purchasing the tools from Toyota is prohibitively expensive, but there seem to be Chinese knock-offs--perhaps some of these companies actually make the name brand equpment now?

Would this device do the job? Home--Euros international commercial limited

Just wondering...

 

Hi Galaxee,

I do appreciate your concern, and your thinking about this with me.

I offer an additional observation: when the car was IG-OFF, the first drain cock that I opened was the CHRS canister drain cock. Probably 5 out of 6 quarts drained came out via that drain cock.

If the water valve was closed to the canister at IG-OFF, and since the CHRS water pump motor was not running during the draining process, wouldn't you agree that only the canister contents would drain via the canister drain cock? IIRC the canister capacity is ~ 3 quarts.

Further, the temperature of the coolant coming out via the CHRS canister drain cock was initially quite cool; subsequently it became hot. This implies that the first coolant being drained came from the radiator; subsequently the canister contents drained.

After draining coolant via the CHRS canister drain, I closed that drain and opened the radiator drain. No fluid came out, so this is further evidence that a path between the radiator and the CHRS canister remained open. Then I opened the engine block drain and only a small amount of fluid came out.

 

the purpose of the CHS water pump is to force coolant in the reverse direction from normal operation for storage. during driving, the pump is off and coolant is able to flow passively through in forward direction while the pump is not running.

what was not directly known, is whether the CHS water pump allows passive flow in the reverse direction during coolant draining. that would mean the cold coolant you drained came from the block and radiator.

however, you just went and inadvertently proved that it does:

sounds to me like the CHS pump allows coolant flow from the engine and radiator through it, even when OFF. recall the path between the CHS tank and the radiator is the one that contains the CHS pump and not the coolant flow control valve. this says nothing of the path between the CHS tank and the head via the coolant flow control valve. we cannot make any conclusions about the status of the coolant flow control valve with this information.

toyota literature hasn't changed its stance on the valve being closed after the CHS pump fills the tank. i have yet to see evidence to contradict that.

not surprising- i'm paraphrasing DH briefly here, but he says in general the first drain you open will drain the most coolant. sounds like the radiator was emptied, and the block didn't quite drain all the coolant through the radiator.

an interesting discussion, for sure. but i still wouldn't go jumping my CHS pump to DIY fill the CHS tank. the valve position is an issue.

 

additionally, DH just dug up his CHS pump (go figure he's got one of those laying around) and was able to blow air through it both ways no problem.

 

Thanks for the update; I don't suppose DH has a valve lying around in the same parts box...

 

Inexplicably, my coolant pump started working yesterday morning! I had messed around with it by jumpering the relay socket but it would not work (only got hot), so I gave up on it. 2 days later when I powered up in the morning, I heard a semi-loud pumping sound like a window washer pump for about 10 seconds before the engine fired up, for the first time since I've owned the car (6 weeks). No check engine light P2601 DTC any more! I also checked it with the relay jumpering method again and it operates every time now. It seems to be getting quieter each time now, but how loud should it normally be?