Understand & Fix P0349: Camshaft Position Sensor B Circuit Intermittent with iCarsoft CR Ultra P

If your vehicle’s check engine light flickers, you experience random stalling, or notice rough acceleration that comes and goes, a diagnostic scan will likely return P0349. This OBD-II code stands for "Camshaft Position Sensor B Circuit Intermittent"—a critical fault targeting the secondary camshaft position sensor (CMP B) and its control circuit. The CMP sensor works with the Engine Control Module (ECM) to synchronize camshaft rotation with ignition timing and fuel injection. An "intermittent" error means the sensor’s signal cuts out, fluctuates, or becomes erratic under specific conditions (e.g., temperature changes, vibration), disrupting engine synchronization.

Basic scanners might only flag a "camshaft sensor error" but can’t capture intermittent signals, test circuit continuity under load, or validate sensor responsiveness—leaving you guessing between a faulty CMP sensor, damaged wiring, or a loose connector. The iCarsoft CR Ultra P, with its OE-level engine diagnostics, bi-directional control, and live data logging, solves this. Below, we break down P0349, its causes, symptoms, step-by-step resolution, and 8 FAQs to answer common troubleshooting questions.

What Is P0349?

P0349 focuses on the secondary camshaft position sensor (CMP B)—a component typically located near the camshaft (on the cylinder head or timing cover) in engines with dual camshafts (e.g., V6, V8, or inline-4 with dual overhead cams). CMP B works alongside CMP A to provide redundant camshaft position data to the ECM. The sensor generates a digital or analog signal as the camshaft rotates; when this signal becomes intermittent (drops out or fluctuates unexpectedly), the ECM triggers P0349. This issue often occurs under specific conditions—such as warm engine temperatures, high vibration, or wet weather—making it harder to diagnose with basic tools.

Key Symptoms of P0349

• Flickering or Intermittent Check Engine Light: The light may turn on and off, especially during acceleration or temperature changes.
• Random Engine Stalling: The ECM loses camshaft position data, causing the engine to shut off suddenly (often at idle or low speed).
• Rough Acceleration & Misfires: Erratic sensor signals disrupt ignition timing, leading to hesitation or shaking when pressing the gas pedal.
• Hard Starting: Intermittent data prevents the ECM from syncing fuel injection and ignition, making it difficult to crank the engine.
• Reduced Engine Power: The ECM may enter "limp mode" to protect the engine, limiting acceleration and top speed.
• Poor Fuel Economy: Incorrect timing from intermittent signals increases fuel consumption by 10–15%.

Common Causes of P0349

Why iCarsoft CR Ultra P Excels at Diagnosing P0349

The CR Ultra P outperforms basic tools with features tailored to intermittent camshaft sensor and circuit diagnostics:

Step-by-Step: Diagnose P0349 with iCarsoft CR Ultra P

1. Confirm P0349 & Gather Data

   Plug the CR Ultra P into your vehicle’s OBD-II port, power on the tool, and select AutoVIN Identify to auto-detect your vehicle’s make, model, and engine configuration.
   Navigate to Engine > Fault Codes > Read Codes to confirm P0349. Tap Code Details for model-specific insights (e.g., "Toyota RAV4: Camshaft Position Sensor B Circuit Intermittent; Signal Dropouts Detected at 2500 RPM; Check CMP B Wiring or Alignment").
   Use the CR Ultra P’s Data Logging function to record CMP B signals during a test drive—captures intermittent dropouts basic scanners miss.

2. Analyze Live CMP & Engine Data

   Go to Engine > Live Data > Timing & Sensors and monitor three key metrics:
   1. CMP B Signal: Should show a steady digital/analog signal. Intermittent drops to 0V or fluctuations confirm P0349.
   2. CMP A vs. CMP B Signals: The two sensors’ signals should be synchronized. A mismatch indicates faulty CMP B.
   3. RPM & Temperature: Note if dropouts occur at specific RPM (e.g., 2000–3000 RPM) or temperatures—narrows down the cause.

3. Test the Camshaft Position Sensor B (CMP B)

   1. Use Bi-Directional Control > Engine > CMP Sensor Test: Send activation commands and simulate rotation. Intermittent responses = faulty sensor.
   2. Locate CMP B: Use the CR Ultra P’s Component Location tool (typically near the rear cylinder head for Bank 2).
   3. Inspect & Test: Check for oil/carbon buildup or loose connectors. Use the CR Ultra P’s Resistance Test (should match OEM specs, e.g., 1k–5k ohms—fluctuating resistance = faulty sensor).

4. Inspect Wiring, Connectors, & Timing Components

   1. Wiring Check: Use Continuity Test and wiggle wires to simulate vibration—intermittent continuity = frayed/loose wiring.
   2. Connector Check: Clean corroded terminals. Use the CR Ultra P’s Voltage Test to verify 12V power and ground to the sensor.
   3. Timing Check: Inspect timing chain/belt for wear. Use the CR Ultra P’s Camshaft Timing Test to verify alignment.

5. Repair & Clear the Code

   - Replace CMP B if tests confirm it’s faulty (use OEM-compatible sensors for signal accuracy).
   - Repair damaged wiring, clean connectors, or adjust sensor alignment as needed. Replace worn timing chain/belt if required.
   - Use the CR Ultra P to Clear Codes and run a Timing Synchronization Test. Log CMP B signals during a follow-up test drive to confirm no dropouts remain.

FAQs: P0349 Troubleshooting