05 Coolant Pump Operation Questions

The CHRS pump is pretty noisy. Sounds like the motor had seized up, but then it decided to free itself. It should always run for several seconds at a cold start. It will usually run several seconds when you turn off the car.

The good news is that you now know exactly what the problem is, should DTC P2601 come back.

 

How long does it run during the self-test 5 hours after the system is turned off?

 

I believe that it will run just for a few seconds. I don't see any spec in the repair manual regarding how long the pump should run during the soak mode test.

 

Three possibilities here.
1. The relay had a poor contact on the pins that plug in. This would limit the power to the pump, allowing it to get warm but not to turn. You fixed that by pulling it out and then pushing it back in after you tried the jumpering.
2. There is something in the coolant that was blocking the rotation of the pump. Somehow you dislodged that (or it dissolved over time).
3. There is corrosion on the pump rotor. Repeated start tries has finally dislodged that so it can rotate.

I vote #1.

 

I had pulled the relay a few weeks before during troubleshooting per the Toyota repair manual, and had good continuity in the wire harness from the ECM to the pump. I vote #2 or #3.

Thanks for your suggestions - this has been an interesting problem that seems to have suddenly fixed itself!

Does anyone know if the warranty still applies to a car that has a salvage/rebuilt title? I have less than 60,000 miles and it's less than 60 months old, which is the specified Toyota powertrain warranty in TSB 0087-08 (abnormal noise from CHS water pump). If it makes noise or works intermittently, maybe Toyota can replace it per this TSB.

 

The warranty does not apply to salvage vehicles; but if you care to test the warranty entitlement system, you could visit your local dealer and see what happens.

 

Hi Prius chatters,
I have an '05 Prius that, sadly, was hit by a deer in the front drivers side bumper. It pushed back the coolant canister and drove the pump into the front tire. My body shop took the car to Toyota, which replaced the pump, bled the system, and "tested the car". When I came to pick up the car the next day (the rest of the body work had been finished) the check engine light was on. He had a friend at a local shop read the code for me, and while I do not remember the number, the description was "coolant pump control circuit voltage". He cleared the code, and it did not come back that day despite 2 shut downs and a restart, but in the second restart it was there. I am not hearing the pump, but it has been so cold and windy here it is hard to tell. My biggest question is how critical is getting this fixed--it's not easy getting this down to Toyota, and I would love to have the ability to wait until after the holiday. Does anyone think this can cause additional harm or should I try to deal with this on Monday? I will obviously make the necessary calls and will not pay Toyota a cent (the body shop already paid them for the repair and testing and I will have him make the call), but with the holiday upon me I really need that car. Any thoughts would be appreciated.

-John

 

Hi John,

Is it possible that you had DTC P2601 Coolant Pump Control Circuit Range/Performance? If so, what this means is that the coolant heat recovery water pump, the relay for that pump, the ECM, or a wiring harness problem is the issue.

You can drive the car without causing further damage over the holiday weekend.

 

Pretty sure it was P2601, but I did think it said "voltage". Anyway, the new pump they put in is either silent or is not pumping (I'm going to guess the latter!) though I detect no other problems with the car. If I can get it fixed on wednesday I will but I doubt that will be possible. Thanks for the reply. I'm guessing Toyota did not turn the car on and off enough to throw a hard code. Boy, even when I don't bring the car to them myself I still hate my Toyota dealer service!

 

I've noticed that mine is not running at "every" cold startup or shutdown.

A few weeks back, if I remember correctly, there was ALWAYS a CHRS noise and a few seconds delay before the ICE kicks in at startup.

But now there is sometimes when the ICE kicks in immediately after I push the Start button and sometimes I hear the pump and I have a delay before the ICE fire up.

I don't have any DTC if I look at it using my Scangauge.

Is that behavior normal or should I go to the dealer ? (temp around here is -10c every morning and I use an EBH two hours before I leave)

thank you

 

Ok I've found this:

It is almost the same behavior as my 2005, so it must be normal.

Now, regarding the sound when cold, mine is also very very noisy. Do you think the T-SB-0087-08 would also apply to Canadian Prius ?

thanks

 

+Patrick Wong,

Sorry to revive the thread. I am getting the P2601 error code (as expected). I was not able to run the pump (was functioning normally prior to coolant change) because, no matter if I used a paper clip or voltmeter, I could not short it out --- it seems the copper wires are buried deep enough I can't reach them. Can you provide a picture of your process of shorting it out?

I'm wondering if it isn't functioning normally because I omitted this from my process.

My CHRS has not run since the coolant change and the error code finally turned on with the weather starting to cool off.

 

The concept is to find and remove the CHRS relay which is located in the small relay box mounted on the firewall over the engine. Then use a paper clip to short the appropriate relay socket terminals, which will provide 12V to the CHRS pump.

Use an ohmmeter to determine which pair of relay terminals are for the relay coil (will measure ~100 ohms) and which pair of relay terminals are for the relay switch (will measure infinite resistance when the relay coil is not energized, then will measure ~0 ohms when the relay coil has 12V applied to it.)

The idea is to use the paper clip to short the relay switch terminals, NOT the relay coil terminals.

You can see that the terminals sticking out of the bottom of the relay are relatively short, so there should be no problem contacting the socket terminals either with a paper clip or the probes of your multimeter.

If this is too difficult of a concept, obtain and use Mini VCI which will provide a screen that allows you to run the CHRS pump via software command.

 

I will review my process with what you've shared here. I suspect I'll have to dig a bit deeper. Will the pump not run after a coolant change if this is not completed? Otherwise I suspect I may have to troubleshoot deeper per your earlier instructions in this thread.

Thanks!

 

The pump should run regardless of whether air is purged out of the system. If air is in the system then the pump will not be effective in moving coolant into the CHRS canister.

 

Patrick,

I was able to successfully short those terminals and re-burped my system (adding coolant as needed) --- the good news is the pump & wire harness are intact. Now I still have that DTC code thrown. If the error is stored (assuming it is since I have yet to clear it) will it bother to turn the pump on and off until then? I didn't hear the pump turn on this morning as I was expecting, but I suspect I need to clear that code to see if everything is operating normally... At least that is how I work some of my own fault logic at work.

My assumption is that, as opposed to leaving fault yet to the relay as it was functioning normally prior to my coolant change.

Thanks again for your insight!

 

OK, clear the logged DTC and see what happens. If DTC P2601 is still current, and you've proven the coolant heat recovery system pump works, then the suspect areas are either the relay (that you pulled when shorting the socket terminals) or the engine ECU.

To test the relay, remove it, apply 12VDC to the relay coil terminals (the ones that measure ~100 ohms) and then measure resistance across the switched terminals. The resistance should be < 0.5 ohms after accounting for the resistance of the digital multimeter leads. If higher, replace the relay.

If the relay is found to be good, then you are faced with replacing the engine ECU or living with the problem.

 

I do know the relay coil terminals measured at 150+ ohms --- I'm a bit electrically illiterate, but that would imply an increase in amp draw on that side to make up that difference; may not matter though. I'll find a way to complete the test on the switched terminals as you have indicated.

Thanks.

 

Actually, if the relay coil resistance is 150 ohms (instead of 100) that means the relay coil requires less current, given a fixed voltage. The relationship is based upon Ohm's Law:

Voltage = Current * Resistance

The voltage applied to the relay coil is going to be around 13V when the Prius is READY.

The critical issue is whether the switched terminals display a very low resistance, when the relay is energized.

 

My tertiary theory is that I may have pressed a bit too hard on female terminals and bent them out enough such that I'm not making contact. If the relay passes I'll do some configuring on that end as well before I decide if its an ECU problem --- I seriously doubt it as it worked perfectly before I did the coolant change to begin with.