Camshaft Position Sensor B Circuit (Bank 2)
The engine's computer can't properly read the camshaft position sensor on the exhaust side of Bank 2 (the side opposite the #1 cylinder). Think of it like a timing clock that's stopped working—the engine doesn't know when to open and close the exhaust valves correctly.
The ECM monitors voltage signals from the Bank 2 camshaft position sensor to verify exhaust cam timing. It compares the signal frequency and phase against crankshaft position to ensure synchronization. If the signal is missing, inconsistent, or out of range for more than a set duration, the fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sensor signal voltage | 0.5–4.8V (switching or analog depending on type) | No signal, constant high/low, or erratic transitions |
| Cam-to-crank correlation | Sensor pulses align within ±5° cam timing | Correlation error exceeds threshold or signal dropout detected |
Code P0390 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0390 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.