Fix P0390: Mechanic’s solutions that WORKED

The OBD2 code P0390 relates to the Camshaft Position Sensor “B” Circuit on Bank 2 of the engine. This sensor plays a crucial role in monitoring the position of the camshaft and ensuring the engine’s timing is correct. When this code is triggered, it indicates a problem with the signal from the camshaft position sensor in Bank 2, leading to potential engine performance issues.

P0390 quick overview

Meaning	P0390: Camshaft Position Sensor “B” Circuit (Bank 2) Malfunction
Is it serious?	Yes, it can lead to noticeable engine performance problems, including reduced power, poor fuel economy, and in severe cases, the engine not running.
Possible causes	– Faulty camshaft position sensor – Wiring or connection issues – Mechanical issues with the camshaft – Control module problems
How to diagnose?	Check the sensor and wiring: Inspect the camshaft position sensor and its wiring for damages or disconnections. Inspect the camshaft: Look for mechanical issues that could affect the sensor’s reading. Verify signal with a scope: Use an oscilloscope to check the sensor’s signal. Review vehicle-specific technical bulletins: For known issues and manufacturer-recommended solutions.

How to fix P0390 – learn from mechanics

I looked into P0390 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: Ram

Vehicle Information 2014 Ram 1500 ST 3.6L

Issue + Repair History

• MIL on, traction icon on, will not go over 60 MPH
• Codes for torque signal implausible and cam sensor, bank 2
• Swapped cam sensors, code stayed with bank 2
• Checked 5v ref and sensor ground, good
• Exhaust cam lobe wiped out, roller follower failed
• Replaced exhaust camshaft, lifters, and followers on exhaust side
• Checked cam timing, cleaned intake cam magnet, installed new OE cam sensor
• Performed cam/crank relearn procedure, updated modules with WiTech 2.0
• P0390 and P0394 returned within 5 miles, limp mode returned
• Scope shows good waveform on both cams, wiring from pcm to cmp good

Other OBD2 Codes + Test Results

• P0390- Cam sensor circuit bank 2
• P0394- Cam sensor circuit bank 2

Mechanic Suggestions

• Check galley plugs behind phasers for tightness or recovery
• Inspect for loose or missing oil galley bolts underneath cam phasers
• Review Star Online Publication S1618000050 for known issues
• Consider insufficient oil pressure as a possible cause

Final Fix

• Found missing bolt on intake cam, retrieved from oil pan
• Tightened exhaust cam plug, checked and tightened bolts on other side

Case #2: Toyota

Vehicle Information 2007 Toyota Sienna LE 3.5L

Issue + Repair History

• Starts then dies like immobilizer
• No current codes, history codes cleared
• Key light blinking slowly, goes out with key in
• Pump runs when cranking, shuts off when engine starts, restarts briefly when engine dies
• Immobilizer eliminated as cause
• Found fuel pump speed resistor with high resistance, replaced

Other OBD2 Codes + Test Results

• P0138: B1S2 heater
• P0345: CMP sensor A B2
• P0365: CMP sensor B B1
• P0390: CMP sensor B B2
• P0606: ECM/PCM processor

Mechanic Suggestions

• Check fuel pump speed resistor connector and wiring for damage
• Investigate ignition switch for power distribution during start and run positions
• Ensure ECM receives tach signal in run position

Final Fix

• Replaced fuel pump speed resistor, corrected high resistance issue

Case #3: Ford

Vehicle Information 2011 Ford F-250 Super Duty XL 6.2L

Issue + Repair History

• Initially had CEL with codes P0390 and P0394 for Cam Sensor Bank 2
• Replaced cam sensor, but two weeks later found Bank 2 timing chain jumped one tooth, bent valves
• Replaced bent valves and timing chain
• Continued experiencing massive oil consumption, despite no codes
• Discovered excessive dust in intake from K&N air filter, suspecting oil getting past rings
• Engine replacement scheduled due to oil consumption

Other OBD2 Codes + Test Results

• None mentioned besides initial cam sensor codes

Mechanic Suggestions

• Check for oil between transmission and engine
• Pull plugs and inspect for oil burning
• Consider engine replacement due to likely damage from oil consumption

Final Fix

• Scheduled engine replacement
• Discouraged the use of aftermarket air filters like K&N due to potential for dust ingestion and oil consumption

Diagnostic Step	Brief Explanation
Check the camshaft position sensor and wiring	Look for any obvious signs of damage or disconnection.
Inspect the camshaft for mechanical issues	Mechanical problems can prevent the sensor from getting accurate readings.
Use an oscilloscope to verify the sensor’s signal	This can help identify if the sensor is functioning correctly.
Review vehicle-specific technical bulletins	Manufacturer advice can provide solutions for known issues with certain models.
Check for missing bolts or loose connections	As seen in the RAM case, missing bolts can cause sensor issues.
Inspect fuel system components	The Toyota case showed issues unrelated to the sensor can cause similar symptoms.
Consider the impact of aftermarket parts	The Ford case highlighted how aftermarket air filters can indirectly lead to engine issues.

In all three service cases, the issues with P0390 led to varied troubleshooting approaches, reflecting the code’s potential to stem from diverse sources. Whether it was a missing bolt in the Ram 1500, a high-resistance fuel pump speed resistor in the Toyota Sienna, or a jumped timing chain in the Ford F-250, each case underscores the importance of thorough diagnostics and considering all possible causes, including those less directly related to the camshaft position sensor itself.