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!