What Does P0390 Mean?
The ECM has detected a malfunction in the camshaft position sensor B circuit on bank 2. This sensor monitors the position and timing of the intake or exhaust camshaft on the secondary cylinder bank (typically the bank that does not contain cylinder 1). A malfunction indicates no signal, an incorrect signal, or a signal that does not correlate with the crankshaft position sensor. The engine may run with reduced power, exhibit misfires on bank 2, or have difficulty starting.
Common Causes
35%
Failed camshaft position sensor B (bank 2) with no output signal
25%
Damaged or disconnected wiring in the CMP sensor B (bank 2) circuit
15%
Oil contamination or debris on the sensor or camshaft reluctor/trigger wheel
10%
Incorrect sensor air gap or misaligned sensor installation
10%
Timing chain stretch or jumped timing affecting cam-to-crank correlation
5%
ECM internal fault on the CMP B bank 2 input
Diagnostic Steps
1
Monitor CMP sensor B (bank 2) signal presence in live data. Verify if the ECM sees any camshaft position data from this sensor during cranking and running. A zero or missing signal confirms a circuit fault.
2
Unplug the CMP sensor B connector and test the sensor: for a Hall-effect type, verify 5V reference and ground at the harness connector. For a magnetic type, measure resistance between signal pins (typically 500-1500 ohms).
3
Using an oscilloscope, capture the CMP sensor B waveform and compare it to sensor A or the bank 1 equivalent. The pattern should be clean with consistent amplitude and correct timing relative to the CKP sensor.
4
Inspect the sensor and its mounting area for oil contamination from a leaking valve cover gasket. Oil can degrade connector contacts and coat the sensor face, weakening the signal.
5
Check cam-to-crank correlation by comparing the CMP and CKP waveforms on an oscilloscope. If the camshaft timing has jumped (timing chain stretch), the CMP signal will be offset from its expected position relative to the CKP signal.
Estimated Repair Cost
$80 - $500
Parts + labor, varies by vehicle and location
The ECM has detected a malfunction in the camshaft position sensor B circuit on bank 2. This sensor monitors the position and timing of the intake or exhaust camshaft on the secondary cylinder bank (typically the bank that does not contain cylinder 1). A malfunction indicates no signal, an incorrect...
The most common cause of P0390 (Camshaft Position Sensor "B" Circuit (Bank 2)) is: Failed camshaft position sensor B (bank 2) with no output signal
Typical repair costs for P0390 range from $80 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The engine will typically still run using the CKP sensor and other CMP sensors for timing reference, but with reduced efficiency and possibly reduced power on bank 2. The vehicle can generally be driven to a repair facility. If the engine runs very rough or timing has jumped, avoid driving to prevent potential engine damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0390 to identify the root cause.
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Quick Info
Category
Powertrain
System
Variable Valve Timing / Engine Timing System
Difficulty
Type
Generic (SAE)
Recommended Tools
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