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Bench Testing Electric EGR Valve?

Discussion in 'Gen 3 Prius Main Forum' started by jimolson, May 16, 2020.

  1. jimolson

    jimolson Member

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    Has anyone attempted to test a Gen III EGR valve on the bench after cleaning it?

    I expended an entire can of brake cleaner (the good, non-CARB compliant stuff) getting this EGR valve cleaned. Now I'm trying to verify on my lab bench that the opens correctly.

    I've determined that the valve has two 21 ohm coils. I expose these coils (together, or separately) to 12VDC but the valve does not open.

    I can feel the solenoid twitching slightly in response to applied voltage, but it is a long way from opening up.

    Before I reassembled the EGR valve I verified that its polished push rod moved freely. After assembly I can pull on the valve stem with a pair of pliers and feel the attraction of the very strong permanent magnet in the coil.

    Is it possible that Toyota is driving this solenoid with a voltage much greater than 12VDC?
     
  2. Raytheeagle

    Raytheeagle Senior Member

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    It is 110 steps, IIRC;).

    So the movements are small:cool:.

    Maybe @ChapmanF has done something in this space before:).

    But if you've cleaned it, and the plunger moved freely, any issues can then be dealt with topside while everything is connected. So easier to deal with(y).
     
  3. ChapmanF

    ChapmanF Senior Member

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    You've made too many assumptions about how the motor works. It's a six-terminal stepper motor:

    [​IMG]

    You supply +12 from your battery to each of the +B1 and +B2 terminals, and make it move by grounding the EGR1, EGR2, EGR3, and EGR4 terminals in sequence:

    [​IMG]

    That illustration is for the signals seen while idling, so that is the sequence to close the valve. Reverse the sequence to open it. You can see that the even (EGR2, EGR4) terminals are the two legs of one coil, and the odd (EGR1, EGR3) are the legs of the other coil, and that at every point in the sequence, each coil is grounded at one leg or the other.

    You can do this with two SPDT toggle switches or pushbuttons, one for each coil (common to ground, each throw to one leg of the coil). Then which direction it moves is just in how you play the switches. 110 steps to get from full closed to full open, and the same to get back again.
     
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  4. jimolson

    jimolson Member

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    Thanks, guys. I plead stupidity.

    This is one instance when my Purdue electrical engineering masters degree failed me.

    I should have taken my clue from the dual bearing assemblies inside the coil assembly. I wondered why someone wasted perfectly good bearing assemblies on the simple task of sucking that magnet into the coil's core.

    Let me go back to pushing my coat hanger through the EGR cooler. That's all I'm smart enough to be doing today.

    Jim Olson
    Indianapolis, IN US
     
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  5. Raytheeagle

    Raytheeagle Senior Member

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    Use a pressure washer and you'll be done in 15 minutes;).

    And a Big Ten guy:).

    We Are: Penn State for me(y).
     
  6. ChapmanF

    ChapmanF Senior Member

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    Hey, even a Boilermaker is not expected to have x-ray vision and just look at a valve and know how it's meant to work. That's where the pictures in the manual (more info) come to the rescue.
     
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  7. Mendel Leisk

    Mendel Leisk Senior Member

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    I found cable TV coax cable (maybe the thinner variety?) about the thickest that would fit. If you hit the wall with the pressure washer, you try a little chemical persuasion too, maybe alternate between the two:

    Stopper one end of the cooler, then pour in a saturated solution of tap-water-hot Oxi-Clean (the powdered laundry additive). Let sit about an hour, till the bubbling subsides, rinse and repeat.
     
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  8. Raytheeagle

    Raytheeagle Senior Member

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    1700 psi is a lot of force to apply to carbon deposits;).

    If you move the wand around to hit the inside, I'm sure you'd breakthrough:).

    In the almost 6-8 I've cleaned with a pressure washer, I've never found its limit (y).
     
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  9. jimolson

    jimolson Member

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    Oh no, not even close.

    At 140k my EGR cooler was liquid-tight with carbon deposits. You couldn't even see the internal honeycomb through the carbon.

    Took it to the coin-operated self wash area of a local Mike's Car Wash and abused the cooler for the entire 10 minute cycle. The water coming from the high pressure nozzle was so hot I could not hold the EGR cooler without a towel around my hand.

    At the end of 10 minutes I was covered from head to toe with soapy water and carbon flecks, but the sucker was still liquid tight. I could see shiny honeycomb on both ends, but still totally clogged. Witth as much force as I could muster I forced the rubber safety grommet on the nozzle directly onto the opening in the cooler.

    Next stop was a local radio controlled airplane hobby shop to purchase .040" and .060" diameter steel rods. Sharpened these rods, equipped them with handles, and meticulously pushed them (with great pressure and some twisting action) through the cavities.

    I can now see daylight through the honeycomb but the passages are exactly .060" in diameter--not quite what Toyota had in mind.

    I'll write more about this later. I'm not done.

    Jim Olson
    Indianapolis, IN US
     
  10. Mendel Leisk

    Mendel Leisk Senior Member

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    (y)
     
  11. Raytheeagle

    Raytheeagle Senior Member

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    Persistence gets this job done:).

    And you've got time on your side as there is nowhere to go;).

    Take advantage and get it done thoroughly(y).
     
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  12. johnnychimpo

    johnnychimpo Active Member

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    so I took your advise and found when I apply voltage to B1 and B2 and add a ground to each egr I hear the motor move.
    When connect test light to the Connector I get 12. I tested the plunger and it moves freely. I cleaned the EGR so I know it snot clogged. what else can I check since everything seems to checks out. I also check the vsv purge valve no hose leaks it gets voltage and when I apply 12 volts the valve opens but when it is connected it does not even though there is 12 volts coming from the connector. recap... I did maintenance on the intake and egr and now facing P0403 and P0441 and P0455.
     
  13. ChapmanF

    ChapmanF Senior Member

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    Well, as you've seen, in the repair manual there are 12 pages of steps you can follow to figure out a P0441, 7 pages of steps to figure out P0455, and 9 pages for the P0403.

    I'm a slow typist and it would be kind of hard to give you the same depth of help you can find there. It still kind of seems like you're looking at the steps (if you're looking at all) and saying "looks complicated, I'll do something else instead", and that just makes it harder.

    Perhaps if you were asking more focused questions related to the material in the manual (like "what does it mean that in step 7 they want me to check x" or "what's the pressure curve in operation D telling me?" or that kind of thing), it would be easier to see how to help you.
     
    #13 ChapmanF, Mar 20, 2021
    Last edited: Mar 20, 2021
  14. johnnychimpo

    johnnychimpo Active Member

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    Got I will go hit the book harder.
     
  15. johnnychimpo

    johnnychimpo Active Member

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    Ok how do I put the car in inspection mode with techstream?

    upload_2021-3-20_13-40-20.png
     
  16. johnnychimpo

    johnnychimpo Active Member

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    Ok inspected EGR and found it to be faulty it will not open I cleaned it and lubed it but still rough to operate. I have ordered a new one.
    I got another issue with my coolant pump. the original that came with the engine failed after a week of use.
    I purchased a new one and installed it but i am getting P261C & B. So I decided to test it and pulled it out and plugged it in to inspect the pump to see if it ran. From what I read 261C and B are basically saying pump is dead but how can that be if it runs when I turn on the ignition? Any thoughts or suggestions? I found this portion confusing how do I add voltage to a relay and test the resistance?

    upload_2021-3-20_16-31-54.png
     
  17. ChapmanF

    ChapmanF Senior Member

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    If you're viewing the manual online, those blue boxes "INFO" like the one you see next to "Put the engine in inspection mode" are hyperlinks, and will take you right to the procedure in question.

    If you are looking at a PDF made from thousands of somebody's web browser print-screens, then of course the blue "INFO" boxes are only ghosts of hyperlinks past, and then you have to be more resourceful and do something like search the PDF for "INSPECTION MODE PROCEDURE". (That exact search will work in this case.)

    That'll lead you through menus "Powertrain / Hybrid Control / Utility / Inspection Mode - 2WD for measuring Exhaust Gas".

    There can be problems that aren't solvable by thinking about what trouble codes "are basically saying", but only by paying attention to what they are exactly saying. That's what you see in the manual as the "detection condition" for each code. There you see that P261B (it's never good form to leave off the P, C, B, or U at the front of a trouble code, that letter is part of the code) means that the tachometer signal coming back from the pump to the ECM indicated a pump speed less than 900 rpm when the ECM wanted it running faster, and the P261C means that the voltage on that tachometer circuit fell below its lower expected limit, which likely indicates a short to ground somewhere, given that the ECM has an internal pullup on that circuit. By contrast, an open circuit would leave the voltage too high (because of the pullup) and that would have given you P261D instead.

    It could indicate a problem in the tachometer circuit of the pump itself, but could also just be run-of-the-mill wiring or connector issues in that circuit from NWP at the pump back to WPI at the ECM. The steps in the manual are a way to figure that out.

    There's more info on the water pump control and tach circuits over here.

    Testing a relay becomes second nature after a while. Look at the diagram for which two terminals are the coil and which are the contacts. All they are telling you to test is that the contacts are open when you are not supplying voltage to the coil, and that they are closed when you are. Any handy source of 12-ish volts will do for the coil. You could use a couple wires and touch one from one of the coil terminals to body ground and the other from a 12 volt circuit in the car to the other coil terminal. If you have a small 12 volt power supply you can use that instead; less dramatic if you accidentally bounce the wires together. It's usually a whatever-you've-got-handy kind of deal.
     
  18. johnnychimpo

    johnnychimpo Active Member

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    Got it. Using the jump start for 12 v power. But I think this is beyond me. Will be taking it to the shop. It's odd that the pump worked fine for a week then quit. Installed new one while doing intake manifold cleaning. Then car over heard. Can't win them all.
     
  19. ChapmanF

    ChapmanF Senior Member

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  20. johnnychimpo

    johnnychimpo Active Member

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    Thanks. So interesting thing I did. While wearing gloves I took the EGR motor apart while pluged in and held it upside to inspect the magnet and the magnet would pop up and down telling me it was working as expected but the egr valve is hard to open with magnet out of the motor housing . But if you push the valve with your finger it works just fine. That being said I feel it is the valve rubing on the magnet causing the failure of the EGR. Also have a new one on the way.