P1387

What Does Code P1387 Mean?

DTC P1387 signifies a detected electrical malfunction within the circuit controlling Variable Cam Timing (VCT) Solenoid #2. The Engine Control Module (ECM) or Powertrain Control Module (PCM) is engineered to continuously monitor the electrical integrity and operational parameters of various engine components, including VCT solenoids. In the context of P1387, the ECM/PCM has identified an electrical anomaly in the specific control circuit for VCT Solenoid #2. This anomaly could manifest as an open circuit (loss of electrical continuity), a short circuit to ground, a short circuit to battery voltage, or a resistance value that falls outside the manufacturer-specified operational range. VCT Solenoid #2 is a critical component of the engine’s variable valve timing system, responsible for actuating the camshaft phaser to alter valve timing. Depending on the engine configuration, Solenoid #2 typically refers to the exhaust camshaft VCT solenoid on an inline engine, or potentially an intake or exhaust camshaft VCT solenoid for a specific cylinder bank (e.g., Bank 2) on V-configuration engines. When this circuit malfunction occurs, the ECM/PCM loses its ability to precisely control the valve timing for the affected camshaft, thereby impacting engine performance, fuel economy, and exhaust emissions.

Common Symptoms

• Illumination of the Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL).
• Rough or erratic engine idle, especially at operating temperature.
• Reduced engine power and acceleration.
• Increased fuel consumption.
• Engine hesitation or stumble during acceleration.
• Difficulty starting or occasional engine stalling.
• In some cases, a noticeable ticking or rattling sound from the VCT solenoid area.

What Causes the Code P1387?

• Faulty VCT Solenoid #2: An internal electrical failure within the solenoid itself, such as an open coil, a shorted winding, or excessive resistance.
• Wiring Harness Issues: Damage to the wiring harness leading to VCT Solenoid #2, including chafed wires, cuts, corrosion, or an open circuit in the power or ground supply wires.
• Corroded or Loose Connector Pins: Poor electrical contact at the VCT Solenoid #2 connector or at the ECM/PCM connector due to corrosion, bent pins, or inadequate terminal tension.
• Short Circuit: The wiring leading to the solenoid may be shorted to chassis ground or to a positive voltage source.
• ECM/PCM Failure: While less common, an internal fault within the ECM/PCM’s VCT solenoid driver circuit can lead to this code.

How to Diagnose and Troubleshoot

A systematic diagnostic approach is crucial for accurately identifying the root cause of P1387:

1. Visual Inspection: Begin by performing a thorough visual inspection of the VCT Solenoid #2 and its associated wiring harness and connector. Look for obvious signs of damage, such as frayed or burnt wires, melted insulation, corrosion on connector pins, or loose connections. Ensure the solenoid is securely mounted. Consult service information to correctly locate VCT Solenoid #2.
2. Check Engine Oil Level and Condition: While P1387 is an electrical circuit code, proper oil level and quality are paramount for VCT system operation. Low or contaminated engine oil can lead to VCT system issues and may even indirectly stress the solenoid, potentially causing premature electrical failure. Verify the oil is at the proper level and is clean.
3. OBD-II Scanner Data Analysis: Connect an OBD-II scan tool and check for any additional diagnostic trouble codes (DTCs), particularly those related to engine misfires or other VCT components. Note any freeze frame data associated with P1387, which can provide valuable context regarding engine conditions when the fault occurred. Clear the DTCs after initial inspection.
4. Digital Multimeter (DMM) Testing – VCT Solenoid #2:
   • Resistance Test: Disconnect the electrical connector from VCT Solenoid #2. Using a DMM set to ohms, measure the resistance across the two terminals of the solenoid itself. Compare this reading to the manufacturer’s specifications (typically 6-15 ohms, but consult service manual). An infinite reading (open circuit) or a reading significantly lower than specified (short circuit) indicates a faulty solenoid.
   • Continuity to Ground/Power (Internal Solenoid Check): While disconnected, check for continuity between each solenoid terminal and chassis ground. There should be no continuity, indicating the coil is isolated.
5. DMM Testing – Wiring Harness:
   • Power Supply Test: With the ignition ON (engine off), measure the voltage at the VCT Solenoid #2 harness connector. Identify the power supply wire (typically a switched battery voltage from a fuse) and verify it receives approximately battery voltage.
   • Ground/Control Circuit Test: Identify the ground or control wire from the ECM/PCM at the solenoid connector. Depending on the system design, this might be a switched ground provided by the ECM. Using the DMM in voltage mode, probe this wire while the engine is running or commanded ON/OFF via a bidirectional scan tool (if applicable). Alternatively, with the ignition OFF and the ECM connector disconnected, test for continuity between the control wire terminal at the solenoid connector and the corresponding pin at the ECM connector.
   • Short to Ground/Voltage: With both the solenoid and ECM connectors disconnected, check for continuity between each wire in the VCT solenoid harness connector and chassis ground. Also, check for continuity between each wire and battery positive. There should be no continuity.
6. Solenoid Activation Test (Bidirectional Scan Tool): If available, use a bidirectional scan tool to command VCT Solenoid #2 ON and OFF. Listen for an audible click from the solenoid. This verifies the ECM’s driver circuit and the solenoid’s mechanical actuation. If the solenoid clicks but still fails electrical tests, the internal electrical fault is confirmed.

Recommended Repairs and Solutions

• Replace VCT Solenoid #2: If the diagnostic tests confirm an internal electrical fault within the solenoid (e.g., incorrect resistance, internal short/open), the most common repair is to replace the VCT Solenoid #2. Ensure to use an OEM or high-quality aftermarket replacement part for optimal performance and longevity.
• Repair or Replace Wiring Harness/Connector: If the diagnostic procedure identifies damage, corrosion, or poor connection in the wiring harness or solenoid connector, the affected wiring or connector pins must be repaired or replaced. Use proper automotive-grade wiring repair techniques, including soldering and heat-shrink tubing, or replace the entire sub-harness if damage is extensive.
• ECM/PCM Replacement: Only consider ECM/PCM replacement as a last resort, after all other potential causes (solenoid, wiring, connectors) have been thoroughly inspected and verified to be functioning correctly. An ECM replacement typically requires specialized programming and calibration.
• Post-Repair Verification: After completing any repairs, clear the DTCs using an OBD-II scan tool. Perform a comprehensive test drive under varying engine conditions (idle, cruise, acceleration) to confirm the repair is successful and that P1387 does not return. In some cases, a specific drive cycle or relearn procedure may be required.