DTC P0661 – How To Service Your IMRC

DTC P0661 – How To Service Your IMRC


The Intake Manifold Runner Control (IMRC_ system found in the Honda / Acura K series engines has to do with the intake manifold and the butterfly actuated runner system that’s been used so often in small displacement motors. Like the B series before it, the K20 has an intake manifold that utilizes two separate runner systems. There’s a long runner and a shorter runner that’s meant to cut over through the ECU controlling the IMRC solenoid.


From 0-4700 RPM the K20 will use the long runners, until the IMRC solenoid is engaged by the ECU which sends 12volts to change over to the short runners from 4700 till redline. This “shift” is usually felt by the driver as a lull in power, before the power picks back up from 4800 RPM onward.

As with any technological advance, there are some negatives to this system. Comprised of many different moving components, the IMRC can encounter problems being stuck, with low or high voltage or general failure. Because the system is made up of the IMRC solenoid, position sensor, vacuum actuator, and valve assembly o-rings, and more, the problems that can arise from the IMRC can be classified as frequent.

Most customers just take their vehicle to Honda / Acura, whose repair bill can exceed well over 1,200 dollars because the intake manifold, intake snorkel and fuel system must be disconnected and removed for service. However you can save quite a bit of money testing this system on your own, and that’s what we’ll be showing you how to do in a 2004 Acura RSX Base Model.


There can be a few causes for your OBDII DTC P0661 trouble code, which translates to the Honda trouble code Intake Manifold Runner Control Valve Position Sensor Circuit Low Voltage. This means that the IMRC valve actuator is receiving too low a voltage signal from the PCM, and not able to open fully or allow the changeover correctly.

This can be caused by a bad IMRC or a bad IMRC solenoid, and could even be caused by the wiring harness or problems with the wiring harness. Today we’ll be showing you How To Service Your IMRC and showing you what terminals or wires you will need to test using your multimeter or voltmeter.

Where is the K20 IMRC?


The IMRC position sensor is located on the valve shaft of the IMRC and allows the PCM to know what exact position the IMRC is at. This valve position sensor also has an armature that moves the IMRC valve and provides the PCM with a linear position signal that lets the PCM know the position when moving.


To begin your testing procedure and learn How To Service Your IMRC, you need to have the key set to the “ON” position so that you can test the wiring and your IMRC unit. Because the sensors in the engine will be powered in this condition, expect more trouble codes when you are done testing. You will want to capture the freeze frame using a scan tool so that you have a good frame of reference to work from. Now go to your engine bay and you will need to locate your IMRC valve and disconnect the electrical connector.

This three pin connector is easily identified and removed, although reaching it with the factory intake manifold in place may prove difficult.


Using your multimeter, measure voltage between IMRC valve position sensor connector terminals A and C, as these are the VCC1 and low reference signals.


You should see 5 volts here by testing the PIN A – a Yellow wire with RED stripe through it, and PIN C a green wire with WHITE stripe. If you do not have 5 volts here, you have a break someplace that needs to be addressed. Move the negative post of your multimeter to the battery negative terminal, and see if there is any change. If you have 5 volts here, then you can move on to the sensor.

Now you will be measuring for resistance between terminal B and C directly on the sensor to see if it’s still good. Using your multimeter, measure the pins directly on the IMRC sensor for resistance.


You should see at least 9.5 kQ Ω worth of resistance here, if not the IMRC must be replaced right away to resolve your P0661 OBDII Trouble code. Once your IMRC valve is replaced, you can clear your OBDII trouble code P0661 and you should have resolved your issue using our How to Service your IMRC article.

Have any questions about the K20A3 or the IMRC, or the trouble code P0661? Leave us a comment below and let us know!


  1. I have a 2003 Honda CR-V. Today the Check Engine Light came on yellow and not blinking. Since I work at an electrical contracting company my co-worker had a code reader and found P0661 as the code. After a good deal of online searching I have become confused as to whether this will simply need valve position sensor replacement or if the connections have simply come loose, or if the entire assembly needs replacement. It’s the difference between about $85 and $400 for me. I am female, not mechanically inclined, and don’t have the tools to fix it but I’d like to buy the correct part so I can at least save money there. Thank you.

    • Hi Kelley, thanks for reading our IMRC testing guide..

      couple of questions for you :

      1. Did this check engine light come up suddenly? or were you working on the intake manifold at all?
      2. Have you recently changed anything or taken the vehicle in for service?

      If not the chances are your valve has failed, or the solenoid has gone bad… If you aren’t mechanically inclined, I would suggest just taking it in and replacing your IMRC valve for your K series Honda CRV.

      Thanks for commenting! Let us know how it turns out!

  2. Thanks for the article, it saved me from buying a new set of harness wire or sending it to a shop. When I pulled the intake manifold, I didn’t see the IMRC connection and pulled it out along with the 3 wires from the socket…

    There is one thing I want to make sure though, when I am testing for 9.5 kQ Ω, should it be terminal A and B instead of B and C (last picture, the IMRC unit). Please let me know, and thanks again.

  3. Thanks for the article, great help.

    I just want to make sure, when you say test for 9.5 kQ Ω by measuring resistance for terminal B and C (last picture), do you mean terminal A and B in the picture since the female end is reversed.

    Let me know for sure, and thanks again for the article.

  4. Awesome article, been looking everywhere for this info to fix my problem! But I have a question, would you happen to have the wire color diagram for the 3p connector for the 2006 Acura RSX. I think they are different color from the 2002-2004 year. Thanks in advance.

    • Hi Jesus, thanks for reading! Sorry we don’t have a color wiring diagram but the pinouts should be the same for your RSX IMRC no matter what year you own! Thanks for reading and commenting! Let us know how it turns out!

  5. Nice write-up! I haven’t done the voltage and resistance testing you suggested, but before I stumbled across your article I replaced the complete IMRC assembly to try to solve the P1077 and P1078 codes my 2006 base RSX was throwing. I couldn’t clear the code via OBDII so I reset the ECU by pulling the engine fuse. While idling the car for 5 minutes, the CEL returned. Any thoughts on where to go next with this? The IMRC seems to have a reputation for being a troublemaker with this car. I’m really bummed that I’ve already spent $270 and this problem isn’t gone 🙁

    • Hi Doug! thanks for reading!

      Sorry to hear about the problems you are having, good news is however there’s just three wires on this harness. If you’ve replaced the IMRC already, then it’s a problem with your harness that’s causing the check engine light to return. Make sure to check for power, ground and test the continuity at the ECU from the signal wire.

      Best of luck to you! Let us know how it turns out! Thanks for commenting!

  6. Nice write-up! My base 2006 RSX was throwing the P1077 and P1078 codes associated with the IMRC, so I went ahead and replaced the entire IMRC assembly before I stumbled across your article. After resetting the ECU and idling the car for a few minutes, the CEL returned. I haven’t yet done the voltage and resistance tests you’re suggesting. Any thoughts on what might be my problem and how to proceed? I’m getting pretty desperate, as I’ve already spent $270. Thanks!

  7. Thanks a lot for the advice, John. I’m having trouble seeing whether my replies are posting successfully, so this one may be a duplicate to one that just hasn’t been approved yet or something. Anyway, I attempted to troubleshoot per your article and comment. My car is a base 2006, and apparently Honda changed the harness from the one in your write-up. My harness only has two wires – a blue one with a red stripe, and a black one with a yellow stripe. With the ignition in the ON position, I got 12 V across the two. Any thoughts on how to proceed or troubleshoot further? I took a few pictures of the harness, wires, and connector, too, if you want to shoot me an email. Thanks again for your help!

    • Hi Doug, hrm okay, please do send over your pics and include your harness side and connector side images as well sir and we can help you check it out! My email is john at prostreetonline.com.

  8. Hello, I really need help. I recently bought an Acura Rsx 2002 and there was nothing wrong with it at first, but suddenly the CEL was on, so I decided to take it to the mechanic and the scanner throw P0661. The mechanic decided to reset the CEL but a day after, the light turned back on. Idk what to do and I am high school student and cannot afford to pay too much money

    • Hi Mario, thanks for commenting.

      Check out the IMRC connection as shown in this guide. Also double check the wiring to make sure that nothing is loose. Unfortunately if these two check out, your Acura RSX IMRC has failed. Although it won’t impact performance much, it should be taken care of.

      Best of luck!