Fix P0394: Mechanic’s solutions that WORKED

The OBD2 code P0394 signifies an intermittent fault in the “B” circuit of the camshaft position sensor for Bank 2 of the engine. This sensor plays a crucial role in monitoring the position of the camshaft and helping the Engine Control Module (ECM) optimize fuel injection and ignition timing.

When this signal becomes erratic, it can lead to engine performance issues, including rough running, a loss of power, and even failure to start. The intermittent nature of this fault poses a particular challenge, as the problem can appear sporadic, making diagnosis and resolution more complex.

P0394 quick overview

Meaning	P0394: Camshaft Position Sensor “B” Circuit Intermittent (Bank 2)
Is it serious?	Yes, this code can lead to significant engine performance problems and should be addressed promptly.
Possible causes	– Faulty camshaft position sensor – Wiring or connector issues (damages, shorts, disconnections) – Engine oil issues (low level, poor quality) – Mechanical damage to the camshaft or related components
How to diagnose?	Inspect the camshaft position sensor and its connector for damage or corrosion Check the engine oil level and quality, as poor oil conditions can affect sensor performance Use a labscope to verify cam and crank signal correlation Inspect the valve train and phasers for mechanical damage or malfunction Ensure all related connectors and wiring are secure and undamaged

How to fix P0394 – learn from mechanics

I looked into P0394 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Jeep

Vehicle information 2011 Jeep Grand Cherokee Laredo 3.6L

Issue + repair history

• Check engine light complaint with codes P0390 and P0394.
• Engine exhibits a distinct rattle noise for a short duration upon restart after sitting idle.
• Previous repairs:
  • Inspected valve train, tightened loose bolts, replaced spark plugs, and both cam position sensors.
  • Replaced exhaust phaser and VVT valve on bank 2.
• Codes persisted despite the mentioned repairs.

Other OBD2 Codes + Test Results

• OBD2 Codes: P0390, P0394.

Mechanic suggestions

• Check oil filter housing for draining back issues.
• Use a labscope to check cam and crank correlation.
• Avoid putting anything magnetic at the rear of the camshaft.
• Inspect camshaft phaser, rocker arms, camshafts, lifters, and oil control valve for damage or malfunction.
• Ensure the engine oil level and condition are satisfactory.
• Verify the condition of the oil filter and its installation.
• Check the intake cam actuator and oil control valve for damage or improper operation.
• Replace the cam phaser if manual movement of the camshaft indicates a faulty lock pin.

Final fix

• Replacing the intake phaser on the driver side (bank 2) resolved the rattling noise issue and prevented the MIL light from reoccurring.

Case #2: Dodge

Vehicle information 2014 Dodge Charger SE 3.6L

Issue + repair history

• Intermittent failure with the MIL lamp on.
• Previous repairs:
  • Throttle body and accelerator pedal sensor replaced by another shop.
• Despite previous repairs, the issue persists intermittently.

Other OBD2 Codes + Test Results

• OBD2 Codes: P2127, P0394.
• Manifold Vacuum Readings: Idle – 19 in.

Mechanic suggestions

• Check the connector for any problematic connections and perform a drag test.
• Inspect the wiring harness for any signs of rubbing, shorting, or improper bracketing.
• Conduct a wiggle test on the wiring harness to identify potential intermittent issues.
• Consider the possibility of a shared reference or ground between the accelerator pedal position (APP) and camshaft (CMP) sensors.
• Monitor the APP reference/grounds to detect any changes during the next occurrence of the issue.
• Record scan data to observe changes in other sensors affected by potential harness problems or sensor issues.
• If no issues are found with the wiring harness or connectors, consider replacing the camshaft sensors with OEM parts.

Final fix

• Replacing the pigtail from the accelerator pedal position resolved the intermittent failure, as one of the wires was making a bad connection.

Case #3: Ram

Vehicle information 2014 Ram 1500 ST 3.6L

Issue + repair history

• MIL lamp on, traction icon illuminated, vehicle unable to exceed 60 MPH.
• Codes for torque signal implausible and cam sensor (bank 2) detected.
• Exhaust cam lobe and roller follower failed, leading to the replacement of the exhaust camshaft, lifters, and followers on the exhaust side.
• Despite replacement, MIL lamp returned with codes P0390 and P0394 indicating cam sensor circuit faults on bank 2.

Other OBD2 Codes + Test Results

• OBD2 Codes: P0390, P0394.
• Camshaft sensor system uses a single sensor on each bank that reads both cams via a magnetic wheel.
• Scope shows a square waveform on both cams.
• Wiring from PCM to CMP checks out.
• Metal flakes found on intake cam magnet, cleaned during repair.

Mechanic suggestions

• Monitor the 5 volt reference and inspect for any issues.
• Utilize an oil filter slicer to examine the media for metal particles.
• Check galley plugs behind the phasers for tightness or possible displacement.
• Confirm sufficient oil pressure and inspect for any obstructions preventing correct cam position.
• Consider low oil pressure as a potential cause for camshaft circuit codes.
• Investigate the possibility of loose or missing oil galley bolts underneath the cam phasers.
• Review Star Online Publication S1618000050 for further guidance on resolving similar issues.

Final fix

• Discovered a missing plug/bolt on the intake cam during inspection, which was retrieved from the oil pan and reinstalled with Loctite.
• Ensured the tightness of the exhaust cam plug and performed the same procedure on the other side preventively.
• No replacement bolt was needed, and the vehicle is running smoothly post-repair.

Diagnostic Step	Brief Explanation
Inspect camshaft position sensors and wiring	Check for physical damage or corrosion that could disrupt signal integrity.
Verify oil conditions	Ensure the engine oil is clean, at the correct level, and of the right specification to maintain proper sensor operation.
Use diagnostic scopes	A labscope can help confirm the correct operation of cam and crank sensors by checking signal correlation.
Check mechanical components	Inspect cam phasers, lifters, and the valve train for any signs of wear or failure that could impact sensor readings.
Address electrical connections	Repair or replace damaged connectors or wiring, especially if physical damage is evident.

These steps, derived from the real-world service cases, highlight the multifaceted approach needed to tackle the P0394 code effectively. From ensuring proper oil conditions to checking for mechanical and electrical integrity, a thorough and meticulous diagnostic process is key to identifying and resolving the underlying issues causing this intermittent fault.

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