The Acura RSX IMRC is otherwise known as the Intake Manifold Runner Control. This control unit is very similar to the earlier DOHC Honda engines, like the B series. Much like the previous models, the IMRC is a valve that opens runners in the intake manifold. This allows for a low throttle and high throttle operation that increases intake velocity and low speed engine responsiveness.
The K20 engine found in the Acura RSX is remarkably responsive and has been hailed for it’s excellent range of torque at low engine speed. This is due to the way that i-VTEC works, as well as the Acura RSX IMRC. This unit opens the larger passages in the intake manifold above 4800 RPM. When this valve fails, becomes clogged or there’s a problem with your Acura RSX IMRC wiring, you’ll see your RSX check engine light turn on.
When you see your Acura RSX check engine light turns on, you will need a OBDII scan tool to retrieve your stored trouble code.
Once you’ve pulled out the OBDII trouble code, it should read as a P1077 or a P1078. Other possible OBDII codes include P0661: IMT Circulation Voltage Low but our test vehicle is a P1077: IMT Valve Stuck Shut.
This OBDII trouble code translates to Intake Manifold Runner Control (IMRC) System Malfunction at high speed or low speed. Either way it’s a serious problem because your 2.0 liter DOHC K series engine isn’t running efficiently.
Today I’ll be showing you how to test the wiring of your Acura RSX IMRC valve in a 2003 model. This vehicle has the OBDII trouble code of P1077 stored in the engine computer, and we’ll begin testing the wires directly.
Of course when you are conducting this test, you will need to use a digital multimeter. If you are not sure on how to use this device, check out our guide here. To begin this testing, you will need to insert the RSX key and turn it to the “ON” position. This will allow you to read the power and ground signals at the Acura RSX IMRC valve.
When the P1077 or P1078 trouble code crops up, you’ll need to test the wiring. In order to do this you will need to open your hood and remove the intake manifold cover to expose the valve and wiring.
Begin by removing the two 10mm bolts that run through the top of the intake manifold cover. These hold the cover in place. Remove these bolts and set them to the side carefully.
Lift up on the intake manifold cover, and make sure to take care around the intake piping. There’s a pin that runs into the top of the intake pipe, so make sure to gently remove the cover.
Once you have the intake manifold cover removed to your i-VTEC 2.0 liter engine, you can now access the vacuum hose and wiring of the Acura RSX IMRC.
Begin testing the vacuum hose by removing the hose and checking for cracks or any signs of damage. Carefully lift up on the IMRC hose to remove from the runners and the plastic guides that hold it in place.
Once you have determined that the vacuum hose shown above is intact and okay, you can begin testing the Acura RSX IMRC wiring. Start by carefully unplugging the three pin harness. This harness is hard to access and there’s not much wiggle room as it’s secured to the alternator.
How does the Acura RSX IMRC fail?
This usually happens when you remove the Acura RSX intake manifold. Many people do this without knowing that the IMRC is still connected. This can cause damage to the signal wire, which again is run past the alternator. The heat generated by the RSX alternator can cause the wires to become brittle and break internally.
Other jobs that can cause your Acura RSX IMRC to fail include replacing your alternator or your RSX starter. Now that you have tested the vacuum hose to the IMRC, you can test the wiring.
Testing your Acura RSX IMRC wiring
Make sure that your RSX ignition is turned to the ON position. Unplug the IMRC connector, and refer to the RSX IMRC wiring diagram below.
Testing the wiring connector is easy, and should begin with PIN 3. With the RSX ignition turned to the ON position, you should have 5 volts of switched power here. If you have a power signal, move onto the ground signal. This is PIN 1 and should be tested by putting the red lead of your multimeter to the positive battery terminal, and probing PIN 1 with the black lead.
If you read 12 volts here, you have a ground signal and your Acura RSX IMRC should have everything it needs to operate. The last thing to check is the signal wire, which runs to your engine computer.
Before you do that however, you should test the IMRC valve directly. To do so check out our guide on how to measure the internal resistance of your Acura RSX IMRC valve. Make sure to check this link before you continue to testing the valve wiring to your engine computer.
Have any questions about our Acura RSX IMRC testing guide? Leave them for us below and let us know!
Hi Pro Street, I had the P1077 trouble code in my RSX after I replaced my starter. When I took off the intake manifold i didn’t disconnect the IMRC valve. After my RSX starter replacement the P1077 check engine light turned on. Please help
Hi Gary, thanks for reading!
If you’ve replaced your starter and this IMRC trouble code pops up, this is a common issue. Chances are you broke the signal wire as shown above. This leads to your ECU so the next steps is to test the continuity between the middle wire and your ECU. Thanks for commenting!
Having the same issue where is the ECU so I can test it and how to test it on the ECU?
Hey Jack, check out this article here :
http://my.prostreetonline.com/2015/01/20/faq-acura-rsx-ecu-pinout/
Replaced starter with same issue check pin 1 and 3 and they are good how do I check pin 2 and where on the ECU and where is the ECU located? Trouble code P1077 only
Hi Jack, the ECU on your RSX is located under the glovebox. the wire you want in particular is called the IMRC signal wire. Here’s a few articles for light reading that should help :
http://my.prostreetonline.com/2015/01/20/faq-acura-rsx-ecu-pinout/
http://my.prostreetonline.com/2014/10/21/dtc-p0661-service-imrc/
Thanks for reading and commenting! Let us know how it turns out!
Having the same issue how do I check the ECU?
Can you list what color wires should be the voltage ground and signal?
The power should be yellow / black and the ground should be black depending on the year. If you own a later model RSX this three pin unit has only 2 wires.
Also, What is the part number for the connector if the connector itself broke?
Hi K, thanks for commenting.
It’s best to head to your local junkyard and pick up a connector replacement for your K series. Thanks for commenting!
Hello, I tested pin 1 and got 5v pin 3 is not reading 12v it’s reading mV only so I figure there is no ground is this correct?
Dina, that would be correct. Try providing the IMRC with a temporary ground to start. If that does the trick then you have a break in wiring somewhere in your RSX engine bay. Start by using a multimeter to find the break and repair it.
Hello, I have this code P1077 on a base automatic 05 RSX, I have checked the power and grounds and everything is good. I replaced the whole intake and still have the code. I replaced the position sensor and still the same problem. What could it be now?
Hi Dina, thanks for reading our guide on the RSX IMRC repair and how to clear P1077 article. Have you checked the wiring from the ECU to the harness for continuity? Often times this wire gets hot and can become brittle. And Im assuming you have also checked the internal resistance of the RSX intake sensor?
I checked the continuity of the three wires coming from the position sensor and all checked out good. I checked the two wires from the solenoid valve and they also checked out good. I checked for vacuum leaks, from rotary valve and it held vacuum. The only thing I haven’t changed are the hoses.
John thanks for the reply, I have checked the wires for continuity and all check out fine. I have since replaced the solenoid valve with a brand new one from honda and the problem still remains the same. I done a vacuum test and the rotary valve is holding vacuum. I have a oem service manual and have followed all the steps in it and still the problem remains. The only thing I have not replaced is the vacuum lines. the vehicle has 217k on the odometer. What size are the vacuum hoses, or should I get them from acura or honda? I am at my witts end with this issue on this car it is my 18 year olds son’s first car and he is regretting getting this car now due to this issue.
if the vehicle needs a new ecu would a hondata be able to not use those sensors and keep the codes from coming back? would it be able to pass emissions here in massachusetts as they scan the ecu for readiness codes and if a code is set they will fail the vehicle.
Thanks I await a reply on this.
So at first I was reading a 1078 code i replaced my solenoid the 1078 code went off now i have a 1077 code but about 6 months ago i replaced the whole imrc valve why am i having this trouble
Hey Matthew, the RSX issues you are describing are actually pretty common. Make sure to check out the wiring from your Acura IMRC to ensure that you don’t have any breaks in the ECU wiring. Hope that helps!
Seem to be getting 12v from pin 3 to the chassis ground, in an ’05 automatic. Any thoughts?
Hi Danman, I would check your ground to ensure that you don’t have an open loop anywhere sir. When you send 5v to the IMRC does it activate? Also have you tested 12v with the IMRC plugged in? Let me know and I can try to help you with your RSX further.
Update: Got it fixed! I forgot to plug the tubing that connects at the T fitting towards the lower end of the intake manifold. Worked no issues after that.
Awesome news Danman! Thanks for reading and commenting on our RSX IMRC testing article!
I had the same issue when changing my starter. The issue now is I can clear the 1077 code and drive forever without any codes coming on unless I shut off the vehicle and restart it right away. I can reset the code and crank it and as long as I don’t turn off the engine the code will not return. Any ideas?
Hi John, thanks for reading our Acura RSX IMRC DIY article.
Have you checked for continuity between the RSX IMRC and the Acura ECU? So if you reset the code and start the car, but then turn it off the P1077 code returns? Is that right? Let me know and I can hopefully assist you further.
Thanks for reading and make sure to please follow us on Facebook!!
Hello, I replaced the starter and got error code P0662 OBD-II Trouble Code: Intake Manifold Tuning Valve Control Circuit High Bank 1. I have check voltage at the connector, but I’m getting nothing on all 3 pins. Also, all hoses seem to be fine and nothing is disconnected. Thanks!
Hi Sean, thanks for reading.
Sounds like your Acura RSX IMRC wiring has been damaged somewhat. Have you tried to backpin the plug once it’s still plugged into your IMRC? Let me know and hopefully I can help. Thanks
Hey John! Thanks for the reply. I just tried back pinning it and actually got power with it unplugged and plugged in. I must have not been making contact before. Ground is 12v. Pin 1 and 2 are at 5v. I still have the error code however.
Sorry, I misspoke about pin 2. Here’s actual readings. Thanks again.
Pin 1 – 12.21v unplugged an 12.21v plugged
Pin 2 – .02v unplugged and 3.68v plugged
Pin 3 – 4.98v unplugged and 4.98v plugged
Hrm.. that sounds interesting Sean, I was going to mention something about the values here until I read your last comment. Hope this pesky IMRC issue gets sorted for you sir!
Odd Sean, okay so after you clear the OBDII trouble code how long until the RSX IMRC check engine light turns on again? is it immediate sir? If so can you try clearing it and then immediately unplugging the IMRC to see if there’s a change in how quickly the CEL triggers?
Hey John, yes the code come on immediately. I also discovered that the diaphragm inside the runner control valve was torn, so went to junkyard and replaced it. I had all hopes this would fix issue, but unfortunately it did not. After speaking with my neighbor that’s a mechanic, he seems to think I damaged a ground wire because the code is for “high voltage”. My next adventure is tracing the ground wire which I found some electrical diagrams for the IMRC UNIT and it goes to point G404 which is somewhere on the chassis. Do you have any insight on where the intake gets grounded or if I’m headed in the right direction? Thanks again for your help.
Hey Sean, yeah that’s a common problem. The issue with the RSX IMRC is that the wiring harness is short at the intake manifold mount point, making it easy for you to stretch / tear or break wiring in the loom. Trace the RSX ground wire back to the ECM and you should be fine! Hope that helps man!
Thanks! Doesn’t the signal wire go to the ECU?
Solved! Ground wire was disconnected in connector but wasn’t pulled out all the way, so I had no idea. I only noticed while I was messing with it and it just fell out. Must have been why backprobing was getting the correct voltage but it wasn’t actually connected to terminal inside connector, so it was reading high voltage. Got a harness at junk yard which has knock sensor and alternator connectors on it for $10. Ugh. Glad this is over. It was a good learning experience though. Thanks for all your help!
Glad to hear Sean! Best of luck to you and glad I could have been of help!
Thanks for this article!
Got the P1077 code.
Not looking to replace the IMRC, as it’s $200+.
Local junkyard does not have RSX’s.
Going to try to clean it.
Question; With what? Carb cleaner?
Thanks again for this article!
Hi Scott, thanks for reading!
Carb cleaner is good, acetone is best!
Good luck on fixing your RSX IMRC!
Took some carb cleaner and cleaned the IMRC.
IT WORKED!!!
Thanks for your page!
However, I now have a code for the thermostat and Oxygen sensor, bank 1 sensor 2
Hey Scott! glad to hear my RSX IMPC guide helped!
If you have the code for the thermostat, which code is it? The oxygen sensor check engine light should go away after some time, the 02 sensor is most likely reading the carb cleaner used when you were cleaning the RSX IMRC out.
Let me know how it turns out! Thanks for commenting!
Would the IMRC solenoid valve throw a p1077 cel code?
Hey Graphics, thanks for reading
Faulty IMRC valves can definitely throw this code, when did your check engine light turn on? Make sure to check out the OBDII section here :
https://my.prostreetonline.com/category/how-to/dtc-obdii/
Hello john,
Getting P1078. Replaced entired intake along with valve. Please help.
What would be the fix if I’m not able to read 12v when testing for ground from pin 1 (black lead) and (red lead ) to the positive terminal on the battery. Please help.
Hey there Benjamin,
Sounds like you have a bad ground, but in this case you are more than likely having a problem with one of the engine ground clusters in your RSX. take a look around and ensure that no groups of grounds have issues. Conversely you can also check continuity in this ground wire. Because this sensor is in a sensitive spot, stretching or wire breaks can occur.
Hope that helps!
I myself am totally dumbfounded with my 2005 RSX Base model , I changed my motor mounts because they were bad and my engine was bouncing around and I could hear it as I drove it . well 3 of the 4 were bad and broken . well i got them all changed and that is where my problem starts. After i got them changed i started the car and the whole entire car is vibrating out of control like a freaking TANK I have checked and redone all mounts and it it is still doing it . I have absolutly NO CLUE what the problem is !!! Love the car and want it fixed!!!!
Hi Dave,
so it sounds to me like you replaced your engine bushings / mounts with aftermarket versions. If you went with polyurethane or upgraded mounts, this stiffness and vibration is normal. If you used factory mounts, something else is definitely wrong. Recheck all your engine mounts, and don’t forget the lower mount that’s connected to your subframe.
Good luck