P1550 IMRC Stuck Open Bank 1
The P1550 code indicates that the Powertrain Control Module (PCM) has detected the Intake Manifold Runner Control (IMRC) system on Bank 1 is stuck in the open position when it was commanded closed. The IMRC system uses butterfly valves in the intake runners to improve volumetric efficiency and air turbulence at low RPM. When the valves remain open, the low-speed charge effect is lost, reducing engine performance and fuel economy.
01. Most Common Causes
- Carbon or soot buildup mechanically blocking the IMRC butterflies open
- Faulty or stuck IMRC actuator (vacuum solenoid or electric motor)
- Failed or out-of-range IMRC position sensor (IMRC Monitor)
- Vacuum leaks in the actuator control hoses (on pneumatic systems)
- Short to ground, open circuit, or high resistance in the control or signal wiring
- Broken, disconnected, or worn linkage rods
- Internal PCM failure (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced low-end torque and sluggish acceleration
- Poor fuel economy
- Possible rough idle or hesitation
03. Step-by-Step Diagnosis
Scan for codes and record freeze frame data
Visually inspect IMRC linkage and actuator for binding or damage
Check for carbon buildup in intake runners; clean if necessary
Test IMRC actuator operation with a scan tool or vacuum pump
Verify IMRC position sensor voltage and compare to specifications
Inspect wiring and connectors for shorts, opens, or corrosion
Check for vacuum leaks in the actuator control system
1. Frequently Asked Questions
Is it safe to drive?▼
Yes, but you may notice reduced low-end power and fuel economy. It is safe for short trips, but should be diagnosed and repaired soon to prevent further issues.
How much does it cost to fix?▼
Repair costs typically range from $150 to $600, depending on the cause. Cleaning carbon buildup is cheaper, while replacing an actuator or sensor can be more expensive.