OBD-II Diagnostic Trouble Code
P0390 — Camshaft Position Sensor B Circuit (Bank 2)
P0390 means the ECM detected a fault in the camshaft position sensor B circuit on bank 2, usually the second cam sensor on that bank (often the exhaust cam on dual-overhead-cam V engines). The exact sensor varies by engine, so check the OEM definition.
Severity 3/5
Less common on commercial trucks
Service this week
Severity
Service this week
Camshaft Position Sensor B Circuit (Bank 2)
Code
P0390
Category
Powertrain
Subsystem
Ignition
Truck-relevant
Less common
What this means for truckers
Service within a few days. Performance is likely degraded. Continuing to drive without service risks additional component damage.
Before you replace parts — try this first
P0390 on the Ignition system is most often failed bank 2 camshaft position sensor b — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Check-engine light, possibly longer cranking, rough idle and reduced power. Variable cam timing on that camshaft may be disabled. Many trucks still start and run with this code.
Common causes
- CommonFailed bank 2 camshaft position sensor B ($120–$450)
- CommonDamaged wiring or connector ($100–$450)
- OccasionalOpen or shorted 5-volt reference or ground ($100–$600)
- RareDamaged target wheel or incorrect cam timing ($300–$3000)
How to fix
Locate bank 2 sensor B in service information and inspect its connector and harness
When to use: First step
Check supply, ground and signal, and scope the output
When to use: To tell a sensor fault from a wiring fault
Replace the sensor
When to use: When wiring is good but the signal is missing or poor
Verify cam timing and target wheel condition
When to use: When a new sensor does not fix it
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0300 — Random/Multiple Cylinder Misfire Detected
- → P0301 — Cylinder 1 Misfire Detected
- → P0302 — Cylinder 2 Misfire Detected
- → P0303 — Cylinder 3 Misfire Detected
- → P0304 — Cylinder 4 Misfire Detected
Frequently Asked Questions
Can I drive with code P0390?
P0390 is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix P0390 on a commercial truck?
Total repair cost ranges $100–$3000 depending on the root cause. The cheapest fix is usually the first one listed below — Failed bank 2 camshaft position sensor B — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0390 fail a DOT inspection?
P0390 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P0390 and related codes?
P0390 is closely related to: P0300 (Random/Multiple Cylinder Misfire Detected), P0301 (Cylinder 1 Misfire Detected), P0302 (Cylinder 2 Misfire Detected), P0303 (Cylinder 3 Misfire Detected). These codes share the same subsystem (ignition) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0390 is set without the companions, the issue is more isolated.
How do I prevent P0390 from coming back after a repair?
For P0390 (Camshaft Position Sensor B Circuit (Bank 2)), prevention centers on the ignition system. Use OEM-spec injectors and spark plugs (gas). Address fuel quality issues immediately — bad fuel kills injectors. Cylinder balance test annually for early warning.