P1520 - FAULT CODE - OBD2

POST UPDATED IN January, 2023

P1520 Code failures by brands

P1520 FORD, LINCOLN, MAZDA, MERCURY: INTAKE MANIFOLD RUNNER CONTROL CIRCUIT FAULT

Description of DTC code P1520

The IMRC (Intake Manifold Runner Control) system consists of a motorized actuator that has a linkage for each engine bank housing. In turn, the linkage is connected to the throttle plate levers. The IMRC housings are the result of an aluminum casting that features two intake air passages for the cylinders. There is always one passage open, while the other opens and closes through a butterfly valve lever. The housing also has a return spring that keeps the plates closed.

The IMRC actuator has internal switches, which send feedback signals to the Powertrain Control Module (PCM), and with these signals, it is possible to know the position of the plates and rods. At less than 3000 revolutions, a solenoid is turned on, which allows the vacuum to be applied to the manifold, thus getting the valve plates closed. And when there are more than 300 revolutions, the solenoid is deactivated and thus the vacuum is vented from the actuator and the valve plates are opened.

The PCM continuously checks the IMRC system for proper operation. If a control circuit failure is found, the DTC P1520 OBDII code will be set.

Symptoms of fault code P1520

  • Check Engine light on.
  • Poor acceleration.
  • Decreased fuel efficiency.

Causes of OBD2 P1520

P1520 OBD2 diagnostic code is set for one of the following reasons:

  • The IMRC actuator circuit wires may have been damaged.
  • The Intake Manifold Runner Control actuator may be in poor condition.
  • The PCM could have deficiencies.

Possible solutions of the DTC code P1520

To troubleshoot the P1520 OBDII fault code you must do the following:

  • As a first step consult the TSB.
  • Check that the electrical components of the IMRC actuator circuit are in good condition. If common damage is found, make the necessary repairs.
  • Check if the Intake Manifold Runner Control actuator circuit voltages match the manufacturer's specifications. If in these tests you discover deficient values, make the necessary corrections.

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