P1391 — Variable Cam Timing Overadvanced (Bank #2)

How do I diagnose P1391 myself?

Start with a scan: confirm P1391, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the camshaft position and variable valve timing, and verify the suspect component against live data before buying parts.

Is it safe to drive with P1391?

Drive with caution. The engine may run poorly or enter a failsafe mode; if timing has jumped, continued driving risks severe valve damage on interference engines. Diagnose before any long trip.

How much does it cost to fix P1391?

Timing chain/belt repair — $800–$2,500; Replace the camshaft position sensor — $120–$350; Replace the VVT oil control valve — $200–$500. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What does OBD2 code P1391 mean?

OBD2 code P1391 flags a problem with the camshaft position and variable valve timing (variable cam timing overadvanced (bank #2)). Short, gentle driving to a shop is usually possible. Common culprits: faulty camshaft position sensor, damaged sensor wiring or reluctor ring, worn cam phaser.

Will P1391 clear itself?

Sometimes P1391 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

When your scan tool displays P1391, the engine's computer has identified that the camshaft timing on Bank 2 has moved too far ahead of its intended position. The code classification is "Variable Cam Timing Overadvanced (Bank #2)" and it falls under the powertrain category, meaning it directly involves engine operation. This fault indicates that the variable valve timing system is no longer maintaining the precise cam position the engineers designed it to hold.

Modern engines use variable valve timing (VVT) to optimize power delivery, fuel economy, and emissions across different driving conditions. The engine control unit (ECU) continuously monitors the actual camshaft position through a dedicated sensor and compares it against the commanded position. When the actual timing exceeds the overadvanced threshold programmed into the software, P1391 triggers. The ECU also captures a freeze frame at the moment of failure, recording engine speed, load, coolant temperature, and vehicle speed—all of which provide valuable clues during diagnosis.

Bank 2 refers to the cylinder bank that does not contain cylinder number one. On V-type engines, this is typically the passenger-side bank. The VVT system relies on oil pressure to actuate a phaser at the cam sprocket, advancing or retarding the cam timing as needed. When this hydraulic mechanism fails to respond correctly, the cam advances beyond specifications, and P1391 results.

Symptoms of P1391

P1391 affects how your engine runs and feels during daily driving. You may notice several of the following:

• Rough idle with noticeable vibration or stumble, particularly when warm
• Decreased low-end torque making the car feel sluggish off the line
• Fuel economy dropping noticeably compared to your normal consumption
• Illuminated Check Engine light on the dashboard
• Reduced overall engine power, especially under acceleration
• Extended cranking time when starting, or multiple attempts before the engine catches
• In extreme cases, the engine may fail to start entirely

Common Causes of P1391

The root causes of P1391 range from simple maintenance oversights to major mechanical failures. Most likely culprits include:

• Dirty or low engine oil—VVT systems depend on clean oil at proper pressure; degraded oil cannot actuate the phaser correctly
• Faulty camshaft position sensor sending incorrect timing data to the ECU
• Stuck or clogged VVT oil control valve (OCV) preventing proper oil flow to the phaser
• Worn cam phaser mechanism itself unable to hold the commanded position
• Damaged wiring harness or connector to the cam position sensor, including corroded pins or chafed insulation
• Worn or jumped timing chain/belt causing the camshaft to rotate independently of its correct position
• Damaged reluctor ring on the cam sprocket distorting the position sensor signal

How to Diagnose P1391

Proper diagnosis follows a logical progression from simple checks to complex repairs:

1. Connect an OBD2 scanner and confirm P1391 is stored in permanent memory. Record the freeze frame data—this snapshot shows exactly what the engine was doing when the fault occurred and guides your next steps.
2. Search for any additional related trouble codes and check manufacturer TSB databases for service bulletins specific to your make, model, and model year—some P1391 issues have known factory fixes or software updates.
3. Perform a thorough visual inspection of all wiring and connectors feeding the camshaft position sensor and VVT solenoid. Look for damaged insulation, corrosion, loose pins, or evidence of heat damage.
4. Verify engine oil level and condition immediately—black, thick, or low oil makes the VVT system inoperable regardless of other components.
5. Monitor live data from the cam position sensor while gently revving the engine. Compare the actual cam angle against the commanded angle to see if they diverge during operation.
6. Clear the code and complete a drive cycle that recreates the freeze frame conditions. If P1391 returns, you have confirmed an active fault requiring physical component replacement.

Repair Options and Costs for P1391

Repair costs vary significantly depending on which component is actually at fault. Working from the least expensive to most expensive options:

• Replace the VVT oil control valve: $200–$500
• Replace the camshaft position sensor: $120–$350
• Timing chain or belt repair including necessary components: $800–$2,500

Always address oil quality and sensor issues before considering timing chain work. The majority of P1391 cases resolve with the first two repairs.

Total Cost to Fix P1391

Overall repair costs for P1391 typically fall between $120 and $2,500 depending on the underlying cause. An accurate diagnosis before purchasing parts prevents wasted money—the most expensive timing chain scenario should be a last resort after confirming no simpler solutions exist. Many independent shops offer diagnostic fees around $100–$150 that apply toward any subsequent repair.

Can You Drive with P1391?

Drive with caution. The engine may run rough, hesitate, or enter a protective limp mode limiting speed and power. If the timing has physically jumped due to a broken timing chain or belt, continued operation risks contact between valves and pistons on interference engines, resulting in catastrophic internal damage. Diagnose and repair P1391 before planning any long highway trips.

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