P1390 — Variable Cam Timing Solenoid B Malfunction

How much does it cost to fix P1390?

Control module repair — $300–$1,000; Repair wiring or connectors — $80–$250; Replace the faulty sensor or actuator — $150–$500. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

How do I diagnose P1390 myself?

Start with a scan: confirm P1390, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the variable cam timing solenoid b, and verify the suspect component against live data before buying parts.

What is the most common cause of P1390?

The most common causes are: faulty sensor or actuator of the affected circuit, blown fuse feeding the circuit, corroded, loose or damaged connector.

What does OBD2 code P1390 mean?

OBD2 code P1390 flags a problem with the sensor and actuator circuits (variable cam timing solenoid b malfunction). The car is usually drivable while you plan the repair. Common culprits: faulty sensor or actuator of the affected circuit, blown fuse feeding the circuit, corroded, loose or damaged connector.

What are the symptoms of P1390?

Drivers most often notice: the affected system operates intermittently or not at all, increased fuel consumption in some cases, possible limp mode depending on the affected component, Check Engine Light on.

Your engine's variable cam timing system adjusts valve timing on the fly, optimizing power output and fuel economy across different RPM ranges. The powertrain control module relies on input from various sensors and commands actuators—including solenoid B—to shift timing as needed. When the control module's self-test detects a problem with solenoid B or its associated circuits, it logs code P1390. Unlike a simple electrical fault, this generic malfunction code means the issue could live inside the component itself, within the wiring, or in rare cases, within the control module's driving software. The module doesn't guess which part failed; it flags the system and waits for you to narrow it down. When P1390 sets, the PCM also captures a freeze frame snapshot—engine RPM, load, coolant temperature, and vehicle speed at the exact moment of failure. That snapshot becomes your starting point for diagnosis.

Variable cam timing solenoids are oil-controlled valves that respond to electrical signals from the ECU. When energized, they redirect oil pressure to advance or retard the camshaft phaser. A malfunction here means timing can drift, overlap excessively, or fail to adjust at all. The engine might run rougher, consume more fuel, or trigger a limp-home mode that limits performance to protect components. P1390 specifically targets solenoid B, which typically handles one bank of cylinders on V-type engines or a specific cam profile on others. The code sets after multiple drive cycles if the self-test fails, so a single glitch won't trigger it—persistent problems do.

Common Symptoms of P1390

• Illuminated Check Engine light on the instrument cluster
• Intermittent operation or complete failure of the variable cam timing system
• Noticeable increase in fuel consumption compared to normal driving patterns
• Reduced engine performance or hesitation under load
• Potential activation of limp mode, restricting RPM and power
• Rough idle or stumble during acceleration in some vehicle applications

What Causes P1390?

• Internal electrical failure of the variable cam timing solenoid B itself
• Damaged, corroded, or loose electrical connector at the solenoid or PCM
• Open circuit, short to ground, or short to voltage in the solenoid wiring harness
• Blown fuse supplying power to the variable cam timing circuit
• Insufficient or interrupted ground connection for the solenoid circuit
• Faulty crankshaft position sensor or camshaft position sensor feeding bad data
• PCM software glitch or internal driver circuit failure (rare)
• Mechanical binding in the camshaft phaser preventing proper actuation

How to Diagnose P1390

1. Connect an OBD2 scan tool and confirm P1390 is stored as an active or pending code. Record the associated freeze frame data—this shows engine speed, load, temperature, and speed when the fault occurred.
2. Pull all stored codes from the PCM. Related codes such as sensor failures or other circuit codes often point to the root cause rather than assuming the solenoid itself is bad. Cross-reference any applicable technical service bulletins for your specific make and model.
3. Perform a thorough visual inspection of the wiring harness routed to variable cam timing solenoid B. Look for chafed insulation, melted sections near hot components, corrosion at connectors, or pins that are bent, spread, or pushed out.
4. If your scan tool supports bidirectional controls, command the variable cam timing solenoid B through its actuator test. A healthy solenoid will click or hum when energized; silence indicates failure.
5. With the connector unplugged, measure reference voltage at the solenoid power terminal, confirm ground continuity at the ground terminal, and verify signal wire continuity back to the PCM. Check for unwanted resistance in the circuit.
6. Perform a wiggle test on the harness while monitoring live data—any signal dropouts or irregularities during movement suggest broken wires inside the insulation that only fail under vibration.
7. After clearing the code, operate the vehicle through a complete drive cycle that matches the freeze frame conditions (similar RPM, load, and temperature). If P1390 returns, the fault is confirmed and persistent.

Repair Options for P1390

• Repair damaged wiring harness or connectors: $80–$250
• Replace faulty variable cam timing solenoid B or affected sensor/actuator: $150–$500
• Repair or replace the powertrain control module (rare): $300–$1,000

How Much Does It Cost to Fix P1390?

The total bill hinges entirely on which part failed. Independent shop labor rates typically run $75–$125 per hour in most regions. Wiring repairs for P1390 are usually straightforward—soldering a broken wire or replacing a damaged connector runs $80 to $250 depending on accessibility. If the solenoid itself is the culprit, expect $150 to $500 for parts and installation on most vehicles. Control module repair or replacement represents the highest cost scenario at $300 to $1,000, but this is rarely the starting point. Across all repair paths, you're looking at an $80 to $1,000 range. Diagnose before you replace—most P1390 faults trace to wiring or the solenoid, not the expensive PCM.

Can You Drive with P1390?

P1390 carries a short-term severity rating. Most vehicles remain drivable with this code set, though you may notice diminished throttle response, higher fuel usage, or a detuned performance mode. Avoid sustained high-RPM operation until the issue is resolved, as variable cam timing faults can allow excessive valve overlap and knock under load. If P1390 appears alongside stalling, no-start conditions, or warnings for braking and steering systems, treat it as urgent and have the vehicle towed rather than risk a breakdown.

Related OBD2 codes

• P1300: Multi-faults - Bank 1 - With Low Side Shorts
• P1301: Multi-faults - Bank 2 - With Low Side Shorts
• P1302: Injector High Sides Shorted Together
• P1303: IDM Failure
• P1304: Cylinder Head Overtemperature Protection Active
• P1305: Boost Calibration Fault