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IMRC testing and operation, P1519 and P1518

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  • IMRC testing and operation, P1519 and P1518

    I decided to put this here because a lot of people are needing to replace the actuator for several reasons (this will be my second time in 2 years). There is a specific procedure on how these are tested by the ECU on a key on/engine off or key on engine run for verification that it moves the secondaries momentarily.

    Upon key on, the computer will send a signal to the actuator to see if the actuator can move the secondaries enough to open them, and the actuator is supposed to send a signal back to the computer via sensor in the circuit board to verify the secondaries are in fact opening. They don't open all the way, but part way At cruise the ecu will continuously test the secondaries momentarily every 5 or so minutes, or more often if the computer has a problem getting the signal back from the actuator. With a slightly lower voltage, if the motor is worn or the circuit board is not sending enough voltage to the motor to drive the secondaries open the computer will try several times to see if there is an issue, Then it sets the code, Usually P1519 stuck closed is more common. Under a part/full throttle condition under load at 3500 rpm, once the ECU commands the IMRC to open the secondaries, and the IMRC opens them, the ECU drops the voltage from 12 volts down to 5 volts to hold the secondaries open as long as the throttle is applied. If the IMRC is bad, or cannot maintain the open position at 5 volts, they close off and will also set the P1519 code.

    Most higher end scanner can command the secondaries to open, but it does that with 12 volts, If the secondaries do open fully, especially at WOT or above 4000 rpm, the computer does not always use that info for verification, The computer uses a smaller voltage to quickly open them just enough to test the system.

    The secondaries will also activate slightly under a heavy load at part throttle under 4000 rpm to get more power, but also operate at rpms above 3500 depending on load and throttle response.

    The engine will bog down if the secondaries close off at acceleration or cruise under certain conditions. This morning I drove the car and accelerated fast enough to cause a part way open, but the secondaries momentarily closed and reopened which I noticed a slight momentary dip in power under part throttle. Similar issue can happen under WOT, where above 3500, power is slightly reduced,.

    The signal coming back from the actuator allows the ecu to send a blip of added fuel to allow no loss of cruise speed or loss of power. If the engine bucks slightly, it also can be the actuator not working properly.

    Also, if the cable has ANY play in it where you can pull it and it move out, the gears are worn out on it. Easiest way to check is to shake it and see if the gears are loose. They should be snug enough to not rattle and the cable not pull out from the normal length of it. Here it will go too far and the sensor in the IMRC won't send the signal back at the right time, or open the secondaries at the right time.
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