P0390
Camshaft Position Sensor B Circuit (Bank 2)P0390 is a generic OBD-II powertrain diagnostic trouble code: Camshaft Position Sensor B Circuit (Bank 2). It is logged by the engine control unit when the ckp/cmp monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0390 means
P0390 is set when the PCM fails to receive a valid signal from the Camshaft Position Sensor designated "B" on Bank 2 — the bank that does not contain cylinder number one. Sensor B conventionally refers to the exhaust camshaft sensor. On V6, V8, and V10 engines with variable valve timing (VVT) on both banks, there are typically four CMP sensors in total; P0390 isolates the fault to the exhaust cam circuit on the secondary bank.
The PCM uses CMP sensor data to phase ignition timing and fuel injection and to control VVT actuator position. A missing or invalid signal forces the PCM into a fixed-timing fallback strategy, resulting in noticeably degraded power and fuel economy. Because the code covers the entire circuit, the fault may reside in the sensor itself, its wiring harness, the connector, the target reluctor wheel on the camshaft, or the PCM input channel. Oil leaks from cam-cover gaskets are a very common culprit — fluid wicks into the connector and corrodes the pins or shorts the signal wire to ground. The diagnosis should start at the connector with a visual and voltage check before the sensor is condemned.
Common causes
Most-frequently reported root causes when P0390 is logged.
-
1
Failed or contaminated exhaust CMP sensor B on Bank 2
-
2
Damaged, corroded, or oil-soaked sensor connector or wiring harness
-
3
Cam cover or valve cover oil leak allowing fluid to wick into the sensor connector
-
4
Missing, damaged, or excessively corroded camshaft reluctor ring teeth
-
5
Open or short-to-ground in the sensor signal wire between sensor and PCM
-
6
PCM Bank 2 exhaust CMP input-circuit failure (less common)
-
7
Incorrect sensor installation or wrong replacement part (wrong air gap)
Symptoms drivers notice
How to diagnose P0390
A typical diagnostic flow when this code is present.
-
1
Scan and record all DTCs plus freeze-frame data; note whether any VVT or timing-related codes accompany P0390
-
2
Visually inspect the Bank 2 exhaust CMP sensor connector for oil contamination, corroded pins, or spread terminals — clean or replace as needed
-
3
With the ignition on, verify the 5 V reference (4.8–5.2 V) and ground at the sensor connector before suspecting the sensor
-
4
Check signal wire continuity from sensor connector to PCM pin; resistance should be near zero with no short-to-power or short-to-ground
-
5
Use an oscilloscope to view the sensor waveform at idle — a clean square or sinusoidal pattern should be present; flat-line or noisy output indicates sensor or wiring fault
-
6
Remove and inspect the camshaft reluctor wheel for missing or damaged lobes/teeth
-
7
Replace the CMP sensor if circuit voltages are correct but waveform is absent or distorted, then retest
Related powertrain codes
- P000A — A Camshaft Position Slow Response Bank 1
- P000B — B Camshaft Position Slow Response Bank 1
- P000C — A Camshaft Position Slow Response Bank 2
- P000D — B Camshaft Position Slow Response Bank 2
- P0010 — A Camshaft Position Actuator Circuit (Bank 1)
- P0011 — A Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)
Frequently asked questions
What does "Bank 2" mean and how do I find it?
Bank 2 is the cylinder bank that does not contain cylinder number one. On most longitudinally-mounted V-engines, Bank 1 is toward the front of the vehicle. Consult your vehicle's service manual for the exact bank layout, as it varies between manufacturers and platforms.
Is Sensor B always the exhaust camshaft?
By SAE J2012 convention, Sensor A is the intake camshaft and Sensor B is the exhaust camshaft on engines with individual sensors per cam. However, some manufacturers deviate from this convention, so always confirm with the OEM wiring diagram before replacing parts.
Can I drive with P0390 until the next service?
Short drives are generally tolerable since the engine will enter a limp-home timing strategy, but extended driving with disabled VVT control risks catalytic converter damage from enriched combustion and poor efficiency. Repair promptly.
Oil is leaking on my cam cover — could that cause P0390?
Yes. A leaking valve cover gasket is one of the most common root causes. Oil travels along the harness into the connector, corrodes the signal pin, and produces an open-circuit fault. Always fix the leak first and replace the contaminated connector pigtail along with the sensor.
Disabling P0390 in software
RaceTune can permanently disable P0390 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
Got P0390 in your scan?
Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.
Upload your file