Camshaft Position Sensor “B” Circuit Bank 2

What P0390 means

Camshaft position sensor 'B' reads the exhaust-side camshaft, and bank 2 is the cylinder bank that does not contain the number-one cylinder. On engines that use it for variable valve timing, the sensor faces a toothed timing rotor pressed onto the exhaust camshaft. As the camshaft turns, the changing air gap between the rotor teeth and the sensor tip varies the magnetic field, and the sensor converts that into a stream of pulses. The ECM reads those pulses to work out exactly where the exhaust cam is, then uses that angle to schedule fuel injection duration and timing and to command the variable-valve-timing (VVT) system. P0390 is the circuit-presence code for that signal on bank 2: it sets when the ECM sees no usable pulse train while the engine is clearly running — on many Toyota applications, no signal for about five seconds at 600 rpm or more. Because the cam angle can no longer be trusted, the VVT controller falls back to a fixed default position and injection timing is calculated conservatively, which shows up as rough running, weak power, or hard starting. Related codes flag the same circuit reading too low or too high in voltage.

Symptoms

• Check-engine light on, often set on a single failed drive cycle because it is a circuit fault the ECM treats as immediate
• Hard starting or long cranking, since the ECM loses the cam reference it uses to phase injection and timing
• Stalling or an unstable idle when the exhaust-cam signal drops out intermittently
• Rough running, hesitation, or a misfire feel as fuel timing and VVT default to a safe fallback
• Noticeably reduced power and throttle response because the variable-valve-timing system holds a fixed default position

Common causes

• A failed or degraded camshaft position sensor 'B' on bank 2 whose pulse output has dropped out or gone weak
• Wiring or connector problems in the sensor circuit — corroded or backed-out terminals, chafed insulation, or an open or short between the sensor and the ECM
• A cracked, deformed, or contaminated timing rotor (reluctor/target wheel) on the exhaust camshaft, so the teeth no longer generate a clean signal
• A VVT phaser or camshaft that has drifted out of its expected position, so the cam signal no longer synchronizes with the crankshaft the way the ECM expects
• Oil contamination on the sensor tip or in its connector from a leaking cam cover or oil-control valve, plus, less often, an ECM or reference-supply fault

Severity & driving advice

Severity: Moderate — The engine may run, but losing the exhaust-cam signal can cause hard starting, stalling, and weak power as VVT and injection default to a fallback.

Can I drive? Drivable but fix soon; may stall or lose power

Diagnostic approach

1. Scan all codes and read freeze-frame — Pull every stored and pending DTC first. Note whether companion codes are present — the low-voltage and high-voltage versions of this circuit (on Toyota, P0392 for under 0.3 V and P0393 for over 4.7 V), the bank-1 equivalent P0365, or crank and VVT codes — because they redirect the diagnosis. Read the freeze-frame to see the RPM and load when P0390 set; the pulse-input fault typically needs the engine turning at 600 rpm or more to run its monitor.
2. Inspect the sensor, connector, and harness — Locate the exhaust-side (B) sensor on bank 2 and unplug it. Check for oil intrusion, corroded or spread terminals, and chafed or pinched wiring. With the key on, confirm the sensor gets its reference supply — Toyota specifies about 4.5 to 5.5 volts on the VC2 feed. Then back-probe or unplug and check the signal wires for continuity to the ECM (below 1 ohm) and isolation from ground (10 kilohms or higher) to catch an open or a short.
3. Check the live signal and waveform — Reconnect the sensor and watch its output with a scan tool or oscilloscope while the engine idles. The signal should stay within its operating range — roughly 0.3 to 4.7 volts on Toyota applications — and produce a clean, evenly spaced pulse train; Toyota's setup views it at about 5 V/division and 20 ms/division at idle. A flat line, missing teeth, or a signal pegged high or low points to the sensor, its wiring, or the timing rotor rather than a false alarm.
4. Inspect the timing rotor and sensor fit — Confirm the sensor is seated fully and torqued correctly, since an incorrect air gap distorts the signal. Inspect the exhaust-camshaft timing rotor (reluctor wheel) for cracks, deformation, missing teeth, or metal debris clinging to it. A damaged or contaminated rotor generates an erratic pulse the ECM cannot use, and it must be corrected before condemning the sensor.
5. Rule out cam timing, then replace and retest — Before replacing parts, make sure the VVT phaser and cam timing are actually where the ECM expects — a phaser stuck off-position or a jumped chain can mimic a sensor fault. Once wiring, supply, rotor, and mechanical timing all check out and the live signal still misbehaves, fit the correct camshaft position sensor 'B', clear the code, and road-test above 600 rpm for a few minutes to confirm it stays away.

Make & model notes

Toyota: Toyota's exhaust-side sensor (the EV signal) is a magneto-resistive type reading a timing rotor on the exhaust cam. P0390 sets after about five seconds with no signal at 600 rpm or more; the signal should stay between 0.3 and 4.7 volts and the VC2 reference feed should read 4.5 to 5.5 volts. Check the rotor for cracks before replacing the sensor.

Jeep: On Chrysler/Jeep V6 and V8 engines the bank-2 cam sensor is a Hall-effect unit reading a target wheel on the camshaft, mounted where oil seepage into the connector is common. Confirm bank 2 orientation from the emissions label, and inspect the pigtail and 5-volt feed before condemning the sensor.

Chrysler: On the 5.7 HEMI and similar V8s, verify the sensor's power, ground, and signal at the connector and rule out a chafed harness near the cam cover. A worn or contaminated tone wheel on the exhaust cam can also drop the signal, so inspect it before replacing the sensor outright.

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