P0390 OBD-II Trouble Code: Camshaft Position Sensor “B” Circuit (Bank 2)

P0390 code definition

The P0390 code is stored if the powertrain control module (PCM) does not detect the camshaft position sensor signal within a few seconds of cranking. This code is specific to sensor “B,” which, in general, is the exhaust camshaft sensor. In most cases, this code is almost identical to a P0345 code, and the two may appear simultaneously.

What the P0390 code means

When the P0390 code is stored, it indicates that the PCM has detected an abnormal or incorrect voltage reading from sensor “B” on the camshaft position sensor circuit in engine bank 2. An electro-magnetic sensor, when sensor “B” is working properly, the teeth on the camshaft will interrupt its magnetic field, giving the PCM data about the camshaft’s position. The PCM then uses this data to calculate ignition timing and fuel delivery. If the input is incorrect, these systems cannot get the proper calculations.

What causes the P0390 code?

In most cases, the P0390 code is stored when engine fluids (such as oil) leak onto wiring, sensors, or electrical connectors. This will generally cause the circuits to be shorted or opened, or it can cause connectors to loosen. In other cases, the cause could be:

• A bad camshaft position sensor (May be accompanied by a camshaft position sensor circuit code.)
• A faulty camshaft position sensor
• A faulty crankshaft position sensor
• PCM failure (rare)

What are the symptoms of the P0390 code?

In addition to illumination of the Check Engine light, when a P0390 code is stored, other symptoms may occur, including the engine:

• Running rough
• Misfiring or stalling
• Losing power when driving or having a lack of power upon start

How does a mechanic diagnose the P0390 code?

Upon detecting the P0390 code with an OBD-II scanner, a mechanic will then begin a visual inspection of the wires and connectors in the camshaft position sensor’s circuit. After repairing or replacing any damaged items in this system, they will clear the code and operate the vehicle. If the code remains clear, the problem is solved. If not, they will then proceed to take further diagnostic steps to inspect and test the camshaft position sensor and the crankshaft position sensor, as well as the PCM if necessary.

Common mistakes when diagnosing the P0390 code

Assuming that the camshaft position sensor is the problem without first checking for fluid leaks and other damage to wiring or connectors will often make this problem more expensive and time consuming than it should be.

How serious is the P0390 code?

In most cases, a problem with the camshaft position sensor will not stop a vehicle from running, but it can make it very difficult and/or dangerous to operate. If your engine stalls while you’re on the road, or if your vehicle is running very rough, the problem could cause a hazard to yourself and others. Furthermore, because the camshaft position sensor “B” provides the PCM with data for fuel delivery and ignition timing, a malfunctioning sensor or a short in the sensor’s wiring could cause problems with fuel efficiency and/or starting the vehicle reliably.

What repairs can fix the P0390 code?

Most commonly, the P0390 code can be resolved and cleared by replacing, repairing, or cleaning wiring or electrical connectors that have been damaged or that have come loose due to engine fluid leaks. Other repairs include:

• Replacing or repairing the camshaft position sensor
• Replacing or repairing the crankshaft position sensor
• Replacing or repairing the PCM (rare)

Additional comments for consideration regarding the P0390 code

If the cause of the P0390 code was an engine fluid leak that caused damage to the wiring, connectors, or any other part of the circuit for the camshaft position sensor, it’s important to determine the cause of the leak. Otherwise, more fluid is likely to leak onto these and other parts, causing even more damage.

Need help with a P0390 code?

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