P1516 indicates the Powertrain Control Module (PCM) has detected an input error with the Intake Manifold Runner Control (IMRC) system on Bank 1. The IMRC uses a butterfly valve in the intake manifold to optimize air flow for different engine speeds; this code means the actual position of the IMRC actuator does not match the commanded position.
The electric motor or vacuum actuator that moves the IMRC butterfly valve has failed, preventing proper position changes.
The position sensor that tells the PCM the actual IMRC valve position has failed or is sending incorrect voltage signals.
Corroded, broken, or shorted wiring harness to the IMRC system, or loose connectors causing intermittent signals.
For vacuum-operated IMRC systems, a leak in vacuum lines or a failed vacuum solenoid can cause improper operation.
The IMRC butterfly valve itself may be stuck, dirty, or physically obstructed from moving freely.
A failed or faulty PCM is possible but extremely rare for this code; it should only be considered after all other causes are ruled out.
The vehicle can typically be driven but with noticeable performance issues including rough idle and reduced power. Prolonged operation may lead to increased emissions and potential catalytic converter damage.
No. Bad fuel does not cause IMRC failures. A severely dirty throttle body may cause similar symptoms but will set different codes (typically P0120-P0220 range for throttle position issues).
PCM failure is almost never the cause of P1516 despite some repair suggestions. The IMRC actuator, position sensor, and wiring issues account for the vast majority of cases. The PCM should only be considered after all other components have been tested and ruled out.
Costs vary significantly by vehicle. IMRC actuators commonly range from $100-$400 for the part, with labor additional. Diagnosis is key—improperly diagnosed repairs can lead to unnecessary parts replacement.