P0394
Camshaft Position Sensor B Circuit Intermittent (Bank 2)P0394 is a generic OBD-II powertrain diagnostic trouble code: Camshaft Position Sensor B Circuit Intermittent (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 P0394 means
P0394 — "Camshaft Position Sensor \"B\" Circuit Intermittent (Bank 2)" — is stored when the PCM/ECM detects an intermittent, non-continuous fault in the camshaft position sensor circuit designated \"B\" on engine bank 2. Bank 2 is the cylinder bank that does not contain cylinder 1, and the \"B\" designation refers to the second camshaft on that bank — typically the exhaust camshaft on dual-overhead-cam (DOHC) engines, or the rear bank camshaft on V-configuration engines. The camshaft position sensor (CMP) generates a pulse train that the PCM uses to determine the precise angular position and speed of the camshaft, enabling accurate fuel injection timing, variable valve timing (VVT) control, and ignition sequencing.
The distinction between P0394 and codes such as P0390 (general circuit malfunction on Bank 2 sensor B) is the intermittent nature of the fault: the signal is not continuously absent or invalid, but drops out or becomes erratic at unpredictable intervals — under vibration, thermal stress, connector movement, or specific RPM ranges. This intermittent behaviour makes P0394 significantly harder to diagnose than a hard fault, as the signal may appear perfectly normal during static testing. Freeze-frame data and the use of a graphing scan tool or oscilloscope under road conditions are often required to capture the dropout event.
Common failure modes include corroded or partially-seated connectors at the sensor, chafed or broken wiring in the harness routing near the cam cover, an internally degrading sensor that loses signal at operating temperature, or oil intrusion into the sensor body. Variable valve timing systems add another dimension: if the VVT actuator or solenoid is malfunctioning, the camshaft may move erratically, causing the signal pattern to appear intermittent to the PCM even though the sensor itself is serviceable.
Common causes
Most-frequently reported root causes when P0394 is logged.
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1
Intermittent open or high-resistance connection at the Bank 2 sensor \"B\" connector — corrosion, bent pins, or a loose connector shell.
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2
Chafed, cracked, or partially broken wiring in the camshaft sensor harness that loses continuity under vibration or thermal cycling.
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3
Failing camshaft position sensor \"B\" with an intermittent internal fault (common at operating temperature or after extended use).
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4
Oil or coolant intrusion into the sensor connector or sensor body causing intermittent signal shorting.
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5
Intermittent loss of 5V reference voltage or sensor ground — degraded PCM reference circuit or poor engine ground strap.
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6
Variable valve timing (VVT) actuator or solenoid fault causing erratic camshaft movement that mimics an intermittent sensor signal.
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7
Damaged or worn camshaft reluctor wheel with a chipped or cracked tooth creating intermittent signal gaps.
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8
Wiring harness routing too close to a heat source or moving component, causing periodic insulation failure.
Symptoms drivers notice
How to diagnose P0394
A typical diagnostic flow when this code is present.
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1
Connect an OBD-II scan tool, retrieve all stored and pending codes, and note freeze-frame data — check RPM, load, and coolant temperature at the time of the fault to identify triggering conditions.
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2
Perform a thorough visual inspection of the Bank 2 sensor \"B\" connector and wiring harness: check for corrosion, oil contamination, bent or backed-out pins, and chafing along the routing path near the cam cover and valve cover.
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3
With the ignition on, perform a wiggle test on the connector and harness while monitoring live cam sensor signal data on the scan tool — a dropout or glitch during the wiggle test confirms a connector or wiring fault.
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4
Verify 5V reference voltage and clean ground at the sensor connector; an absent or unstable reference voltage points to a PCM circuit or wiring fault rather than the sensor itself.
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5
Use an oscilloscope to capture the sensor waveform during a road test or during the conditions that triggered the fault (specific RPM range, cold vs. warm) — an intermittent missing pulse or noise burst confirms sensor or reluctor wheel failure.
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6
Inspect the camshaft reluctor ring for damage (chipped or cracked teeth) if the waveform shows inconsistent pulse spacing.
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7
If VVT codes are present alongside P0394, diagnose the VVT system (solenoid, oil pressure, actuator) before replacing the cam sensor.
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8
Clear codes and perform an extended test drive under the triggering conditions; if the fault recurs with a healthy connector and wiring, replace the camshaft position sensor \"B\" on Bank 2 and 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 is the difference between P0394 and P0390?
P0390 is a general circuit malfunction code for Bank 2 camshaft position sensor \"B\" — the signal is absent or out of range on a persistent basis. P0394 is specifically the intermittent version of the same circuit, meaning the fault occurs and clears unpredictably. P0394 is typically harder to diagnose because the circuit may test normally when static.
Why does P0394 come and go without a noticeable symptom?
Intermittent cam sensor faults often cause brief signal dropouts that the PCM compensates for using the crankshaft position sensor data and stored VVT maps. The engine may continue running normally during a short dropout, but the PCM still records the event as a fault. As the dropout frequency or duration increases, drivability symptoms become more obvious.
Can P0394 trigger on a Bank 2 sensor B if my engine only has one camshaft per bank?
On single-overhead-cam (SOHC) or OHV engines, the \"B\" camshaft designation may refer to the bank 2 cam sensor itself, rather than a second cam on that bank. The code is still valid — it simply indicates the Bank 2 cam sensor circuit, not necessarily a second, separate camshaft. Check the vehicle's service manual to confirm sensor location.
Should I replace the sensor immediately when P0394 appears?
Not necessarily — because P0394 is intermittent, the fault may lie in the connector or wiring rather than the sensor. Follow the diagnostic steps systematically: clean the connector, verify reference voltage and ground, and perform a wiggle test first. Replacing a perfectly functional sensor before addressing a corroded connector will not resolve the fault.
Disabling P0394 in software
RaceTune can permanently disable P0394 — 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.
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