Testing Gen 3 Water Pump

Hey what’s the best way you can recommend to test that with a regular voltmeter?

 

Depends what regular meter you're using. Have I asked that before?

Some meters have frequency counter modes. Some will also measure pulse duty cycle. Some won't, but do have AC volt modes, which might be "true RMS", or something else (sometimes a calculation that works out to RMS but only for sine waves). A pulse train ain't much like sine waves, but depending on the meter, you might end up able to kind of estimate a duty cycle from that.

It might be handy to have a resistor around of a suitable value to use as a pull-up, in place of whichever end of the original circuit has the built-in one (remember that's the pump end for WPO and the ECM end for WPI).

I think rjparker might have been suggesting that really nobody else has had the same problem. You can find threads where people's Gen 3 water pumps reached end-of-life, but that doesn't seem like the problem you're having. You've tried multiple water pumps and you're reporting something wonky in the control of them, in a car where all the underhood wiring has been poked and pulled at in an engine swap, and you'll probably make more progress just by investigating the issue you have than by asking other people whose issues weren't that.

I understand the feeling of crunched for time, but it almost never helps to skimp on the up-front effort to understand the system you're looking at. There's more to it than relays, and I don't think you've posted anything that looked like the relays were the problem. We're probably going to need the full picture of what's going on in the power and control circuits.

 

Yes I am talking about your water pump. While I gave you three different solutions that have worked for others, I could just suggest your ecm is bad. Would that be better? Even if it was most likely but not guaranteed?

Usually one should rule out the other possibilities. Wiring is a common solution but you seem confident you have checked that. So I assume you checked those control signals at the ecm and buzzed them out to the water pump.

A bad water pump is obvious as well but you have seemed to rule that out as well by use of multiple pumps. I believe the aftermarket pumps have often failed to work right out of the box. A genuine OEM without jumping it with 12v would be my choice here.

Chapman has done a good job of presenting the repair manual's oscilloscope captures of the rather precise control signals. It might be worth paying someone to check those signals. I would do that long before hacking in a thermally controlled 12v to your pump.

 

I’ll send a pic of my meter.

 

And how do I show you the full picture what’s going on with the power and control circuits? I do have pictures of the scanner read outs with the codes on the web that help if so here they are.

 

This is a meter I have that reads frequency and duty cycle. As Chapman indicates, frequency accuracy on a square wave would be questionable. If you had a known good Prius it would be reasonable to compare readings. Certainly a zero frequency would be bad as would a constant high or low voltage in dc voltage mode.


There are a variety of acceptably spec'd usb scopes in the $100 - $200 range that require a pc. Hantek has several in the price range. Picoscope is the premium brand with at least one for less than $200. Be sure they have ac coupling. They have a learning curve as would any oscilloscope so a pro diagnosis might be more cost effective.

 

Not by sending pictures of code scanners and trouble codes. Those don't show us what's going on at the four wires that power and control the pump. Someone's going to need to gather that information.

Since you did send the codes, I can confirm that one of them does pertain to the water pump. The P261B means that the ECM thinks the pump is doing less than 900 RPM, at a time when the ECM would like it to run faster than that.

Those other codes are not water pump related, but all three of them lend some support to rjparker's idea that maybe the engine-bay wiring has not come through the engine swap unscathed.

As you think through what I suggested back in this post, you'll realize a full picture of what's going on there is going to have to include voltages, duty cycle on WPO, and frequency on WPI. So you were on the right track a few posts ago when you asked about how much of that you'll be able to read with the meter you've got. (Of course I can't answer that without knowing more about the meter you've got.)

I see rjparker has beat me to posting some information about meters that would be adequate. Sometimes, with some extra effort, you can get what you need with a less fancy meter; for example, a meter without a "duty cycle" mode but with "true RMS" AC would let you estimate duty cycle of a pulse train, using a bit of math.

If it turns out you just haven't got the equipment that could give the needed picture, then it may be necessary to obtain/borrow/rent equipment that can, or obtain/borrow/rent a person who has equipment that can.

It'll also be helpful to know in more detail what your Techstream setup does and doesn't do. If I remember right, at one point you were saying it wasn't connecting to anything, but you screenshotted a screen before it even tried to connect to anything, and you were able to supply more information after that. (Or maybe I'm thinking of somebody else's thread.)

We'd be flying a lot less blind if you could get to the Engine and ECT Data List and Active Tests.

 

I did run techstream , health check . Ecu reprogram, and active test. The health check came back with P261b , active test could not engage the pump, reprogram no noticeable change, and my cheap Walmart voltmeter shows 0v on the pos, 14.5v green wire, 0.03v blue wire, ground is good continuity. Checked all wires all the way back to ecu for continuity-good. So beats me like a tornado IDK

 

You seem to be kind of fixated on the idea of ECM programming being your issue, which I am guessing to be about as likely as Martians.

It is good to know that you have Techstream. What else has it shown you? In the Engine and ECT data list, with the car in READY and the cabin heat turned up, what do the Elec Water Pump Target Spd and Elec Water Pump Spd show?

How about after you clear the P261B? How quickly does it return? What do you see for Target Spd and Spd in the meantime?

When you say "active test could not engage the pump", tell us what you did and what you saw. Was there an error message? Did the active test switch to ON but the pump didn't run? What?

Are you saying 0 volts on the (fatter) blue wire? That could be a problem right there. The smaller blue (WPO) circuit is pulled up at the pump, so if the pump's not powered, that explains WPO as well. What happens if you jumper terminals 3 and 5 at the water pump relay socket?

Also, where are your meter leads when you are taking these measurements? Are you pushing backprobes into the water pump connector? Or where?

 

Zero on pos(itive) is bad. There is a relay and fuse in that circuit. Measure dc voltages from chassis to pin 1. Then chassis to pin 5. Record those two values. Measure dc voltage from 1 to 5 with pin 1 being the positive meter lead. Record that value.

14.5 vdc on green makes no sense based on the above diagram unless the semiconductors on that line have failed. Pins 2 and 4 are pulses, part of the communication to and from the ecu. Measuring dc voltages on those two pins won't help.

I offered better meter or scope suggestions above. Assuming the easy thing is good, eg power to pins 1 and 5, there are still good explanations such as a) the aftermarket pump(s) are incompatible on their pulse communication or b) the pump electronics have failed or c) ecu hardware failures have occurred on the pins associated with the pump.

An oscilloscope is called out in the repair manual to make those determinations.

 

The pins your referring to are in the under hood fuse box correct? The diagram/schematic I’m not versed well in. I would need to study it or take a course. But if I see a picture with a wire harness and the pins numbered I think I could go from chassis to pin # . I’m thinking the way your directing me is possibly the way that I measured it. The illustration I used looks different pic below. Thanks for the response. I do appreciate the helping hand.

 

It had no movement. You can tell when it’s running you can hear it . Also I took it out of the car so I could visually observe. While in active test mode I checked the voltage which was zero. My meter leads were in the wire and on the chassis . Neg on chassis/ pos on the wire. Fat blue wire 0 volts. P261b returns right away. Terminals 3&5 where are those ? That sounds like a better test. Can you direct me please? And thank you again for helping

 

The pins on the water pump while in the car.

 

What do you mean by "on the wire"? I hate to sound like a broken record, but the details really matter.

At the risk of sounding silly, the wire is, of course, insulated. You can't just put a meter probe "on" it just anywhere and get a reading. You need a place where you can probe the copper. That would be at the water pump end, or at the ECM end (and both of those ends have waterproof terminal seals you would need to get around with a backprobe), or at the DA2 connector in the fusebox, or some place where you scraped off or pierced the insulation (not recommended). We can't follow along with what you're doing if you're too vague.



You already know where the water pump relay is, right? Relay blades 3 and 5 are the switching contact ones (1 and 2 are the coil), as shown in the diagram. I'm pretty sure the coil terminals are a bit narrower, if you're not looking at a drawing or seeing numbers molded in.

 

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Although the schematic/diagram does help me get an idea of current routes and connections it doesn’t help me locate which blades to connect my tester to or that I can jumper. And I just stick my probe in the wire piercing the plastic when I test for current. No problem for me . Look no offense but if it’s so aggravating for you help me out you don’t need to. I can ask anyone else. I really don’t look forward to responses . They seem very very unnecessarily condescending and unkind. So if it’s no bother just don’t respond. This is just prius chat. Not prius roast.

 

You get what you pay for unless its free.

The Toyota TIS site does have connectors, wiring diagrams, harness maps, theory, repair procedures etc. You have to pay a minimum of two days access but you can download and keep the pdfs. Toyota is extremely comprehensive on that site, so it takes a bit of a learning curve to get around the thousands of diagrams. Using it online is ideal as they have hot links throughout.

The following composite with connectors was cut and paste from six different pages. The ecu connector you need is A57. By the way if Chapman or a couple of others charged their professional hourly rate, this would be about $200 worth of work. Sometimes its cheaper to grin and bear a little aggravation. You have to show some progress as well. There is a reason why the dealer's service bays are full.

 

No offense taken. Because PriusChat threads become permanent resources for others, it's still possible I might chime in from time to time to clarify things that could throw off future readers with similar issues, but otherwise I'll leave the lifting to others. Here's to swift resolution of your issue.

 

Your are right and I definitely appreciate when someone is lending a helping hand . I’m so sorry if I caused any problems for anyone It was not my intention. If you could just imagine somebody working on two cars trying to get back to work losing money pulling their hair out and banging their head against the wall on a regular basis lol. In the process I inadvertently kind of make others feel like I wasn’t really paying attention to their responses. So I do apologize and thank you again for all your hospitality and efforts. I’m going use the pics you sent and hopefully I’ll figure it out. Hopefully

 

Well after testing everything I could - relays, wires, water pumps I couldn’t find the root cause why the water pump wasn’t getting any power . So I gave up on that for now and installed a Davies Craig EWP controller that works pretty well. It uses PWM(pulse width modulation)like the Prius ECU and isn’t fickle about a specific pump gen 3 or 4 . I can set the peak temp , it has an over or under temp alarm and it pumps at half speed in stages until it reaches your desired peak temp then it pumps full on until the temp is 10 deg under. Its a super easy install. This way I can drive to a shop and avoid a killer tow bill and if they can’t figure it out it will still work. It maintains a temp between 176 -200 even when I hammer It. I also installed a small booster pump from a gen 2 that recirculates the head and block coolant to avoid hot spots which I think will make it easier for the main pump. It does draw a pinch of cooled coolant through a tee from the lower hose by a one way valve to avoid heating the coolant before it reaches the thermostat. It seems to work great so far my only concern is that it might be too cool. And the fans still work with the cars own temp sensors so I guess if there’s any issues I can raise or lower my peak temp setting. I’ll see how it goes