P1517

What Does Code P1517 Mean?

DTC P1517 signifies an Intake Manifold Runner Control (IMRC) Input Error on Bank 2. The Engine Control Module (ECM), also known as the Powertrain Control Module (PCM), sets this code when it detects a discrepancy or malfunction within the IMRC system for the second bank of cylinders. The IMRC system is designed to optimize engine performance by varying the length of the intake manifold runners. At lower engine speeds, longer runners increase air velocity and enhance torque, while at higher speeds, shorter runners improve airflow for maximum horsepower. The ECM commands the IMRC actuator (often vacuum or electrically controlled) to a specific position (e.g., open or closed flaps). An integrated position sensor provides feedback to the ECM regarding the actual position of these runners. When the ECM detects that the actual position reported by the sensor does not match the commanded position within a specified timeframe and tolerance, or if the sensor signal is outside its expected operating range, P1517 is triggered. Bank 2 refers to the cylinder bank that does not contain cylinder #1 (typically the passenger side on many transverse V-engines or the driver’s side on some longitudinal V-engines).

Common Symptoms

• Illuminated Check Engine Light (MIL).
• Reduced engine power or poor acceleration, particularly noticeable at specific RPM ranges.
• Rough idle or engine stumbling.
• Decreased fuel economy.
• Hesitation during acceleration.
• Possible increased exhaust emissions.

What Causes the Code P1517?

• Faulty IMRC Actuator (Bank 2): The electric motor or vacuum diaphragm responsible for moving the runner flaps may be seized, weak, or unresponsive to ECM commands.
• Malfunctioning IMRC Position Sensor (Bank 2): The sensor provides inaccurate or no feedback to the ECM regarding the actual runner position. Often, this sensor is integral to the actuator assembly.
• Vacuum Leaks: For vacuum-operated IMRC systems, compromised vacuum hoses, a ruptured actuator diaphragm, or intake manifold gasket leaks on Bank 2 can prevent the actuator from moving the runners correctly.
• Wiring Harness or Connector Issues: Open circuits, short circuits (to ground or voltage), or high resistance in the power, ground, or signal circuits connecting the IMRC actuator/sensor to the ECM on Bank 2.
• Sticking or Obstructed IMRC Runner Flaps (Bank 2): Excessive carbon buildup within the intake manifold or mechanical binding can prevent the runner flaps from moving freely, even if the actuator functions correctly.
• ECM/PCM Failure: While less common, an internal fault within the ECM could lead to incorrect command signals or misinterpretation of sensor feedback.

How to Diagnose and Troubleshoot

A systematic approach is crucial for diagnosing P1517:

1. Retrieve and Analyze Freeze Frame Data: Connect an OBD-II scan tool and record all available freeze frame data associated with P1517. This data provides valuable insight into engine operating conditions (RPM, engine load, temperature, etc.) when the fault occurred, helping to replicate the conditions.
2. Visual Inspection:
   • Locate the IMRC actuator and linkage on Bank 2. Inspect for any obvious signs of damage, disconnections, loose bolts, or obstructions (e.g., carbon buildup) that might impede flap movement.
   • If applicable, inspect all vacuum lines connected to the IMRC system on Bank 2 for cracks, kinks, disconnections, or signs of dry rot.
   • Examine the electrical connector at the IMRC actuator/sensor for corrosion, bent pins, or signs of damage. Trace the wiring harness for chafing, exposed wires, or strain.
3. Functional Test with Scan Tool:
   • Using a bidirectional scan tool, navigate to the IMRC system and attempt to command the actuator on Bank 2 to cycle through its positions (e.g., “open” and “closed” or specific percentages).
   • While commanding the actuator, monitor the IMRC position sensor feedback PID (Parameter ID) on the scan tool. The reported position should smoothly change and correspond accurately to the commanded position.
   • Listen carefully for the audible clicking or whirring of the actuator as it moves. If vacuum-operated, verify vacuum is being applied to the actuator.
4. Electrical Diagnostics with a Digital Multimeter (DMM):
   • Power Supply: With the ignition ON and the IMRC connector disconnected, measure voltage between the power supply pin(s) for the actuator/sensor and a known good chassis ground. Expect battery voltage (for actuator) or a reference voltage (e.g., 5V) for the sensor, as specified in the service manual.
   • Ground Circuit: Measure resistance between the ground pin(s) of the connector and a known good chassis ground. Resistance should be less than 5 ohms.
   • Signal Circuit: Backprobe the signal wire from the IMRC position sensor (with the connector connected and ignition ON). If possible, manually move the IMRC linkage (if accessible) or command the actuator with the scan tool. Observe the voltage fluctuations; a smooth, linear change in voltage (e.g., 0.5V to 4.5V) is expected as the position changes.
   • Continuity and Shorts: Disconnect the vehicle battery. Disconnect both the IMRC connector and the ECM connector. Perform continuity checks between corresponding pins of the IMRC and ECM connectors to verify no open circuits. Check for shorts to ground and shorts to power in all IMRC-related wires.
   • Actuator/Sensor Resistance (if applicable): With the IMRC connector disconnected, measure the internal resistance of the actuator motor windings or across the sensor terminals. Compare values to manufacturer specifications.
5. Vacuum System Test (for vacuum-operated IMRC):
   • Disconnect the vacuum line from the IMRC actuator (Bank 2). Use a hand-held vacuum pump to apply vacuum directly to the actuator. The actuator rod/linkage should move smoothly, and the actuator should hold vacuum without leaking down.
   • Check the vacuum source line for adequate engine vacuum, typically 18-22 inHg at idle, using a vacuum gauge.

Recommended Repairs and Solutions

Based on diagnostic findings, the following repairs are commonly indicated for P1517:

• Replace the Faulty IMRC Actuator (Bank 2): This is a very common failure point. Ensure the new actuator is properly indexed and secured to the intake manifold, and that any linkages operate smoothly before final assembly.
• Clean or Replace Sticking IMRC Runner Flaps: If carbon buildup or debris is preventing the flaps from moving, the intake manifold may need to be removed for thorough cleaning. This often necessitates replacement of intake manifold gaskets. In severe cases, the entire intake manifold assembly may require replacement if the flaps or their pivot points are damaged.
• Repair or Replace Damaged Wiring Harness or Connectors: Address any identified open circuits, short circuits, or high-resistance areas in the wiring. Replace corroded connectors using appropriate crimping tools and heat-shrink connections for durability.
• Repair Vacuum Leaks: Replace any cracked, brittle, or disconnected vacuum hoses and repair any vacuum leaks affecting the IMRC system on Bank 2. Test the integrity of the vacuum reservoir if present.
• Replace the IMRC Position Sensor (Bank 2): If the sensor is found to be faulty and is a separate component from the actuator, replace it according to manufacturer procedures.
• ECM/PCM Reprogramming or Replacement: Only consider this after all other possibilities have been meticulously ruled out. If the ECM is replaced, it will require specific programming to the vehicle’s VIN and options.

Mechanic’s Tips:

• Always refer to the vehicle-specific service manual for precise wiring diagrams, component locations, and exact voltage/resistance specifications, as these can vary significantly between manufacturers and models.
• When working on the IMRC system, especially if removing the intake manifold, ensure all gaskets are replaced to prevent future vacuum leaks or sealing issues.
• Pay close attention to the “Bank 2” designation. Confirm which side of the engine corresponds to Bank 2 for the specific vehicle you are working on to avoid misdiagnosis and unnecessary component replacement.
• After any repair, clear the DTCs from the ECM and perform a comprehensive drive cycle that includes varying engine speeds and loads to ensure the IMRC system operates correctly and the code does not return.
• Consider checking overall engine vacuum with a dedicated vacuum gauge, as general engine vacuum issues can sometimes indirectly impact vacuum-operated IMRC systems.