Skip to content
Skip to content

OBD-II Code

P0399

Severity

Not yet reviewed

Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.

Can you drive it

We cannot say

Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.

Indicative cost (USD)

$200–$1,800

From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.

P0399 means the Camshaft Position Sensor B circuit is signaling intermittently (alternate manufacturer code, paralleling P0369 in the SAE J2012 standard) — the secondary CMP sensor on bank 2 of a dual-bank engine, or the exhaust-cam CMP on a DOHC layout, is dropping out, glitching, or losing reference long enough for the PCM to flag a fault and then recovering before steady-state failure.

How a shop works this

Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.

  1. Note every code that is set, not just this one.

    Codes that appear together usually narrow the cause faster than any one of them read alone.

  2. Read the freeze frame — the conditions the fault was recorded under.

    Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.

  3. Confirm the fault is current rather than history.

    Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.

  4. Then follow the diagnostic notes further down this page, in the order they are written.

    They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.

If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.

Common symptoms

  • Check engine light
Read the full diagnostic procedureP0399 means the Camshaft Position Sensor B circuit is signaling intermittently (alternate manufacturer code, paralleling P0369 in the SAE J2012 stand…

P0399 means the Camshaft Position Sensor B circuit is signaling intermittently (alternate manufacturer code, paralleling P0369 in the SAE J2012 standard) — the secondary CMP sensor on bank 2 of a dual-bank engine, or the exhaust-cam CMP on a DOHC layout, is dropping out, glitching, or losing reference long enough for the PCM to flag a fault and then recovering before steady-state failure.

Cheapest-first ladder

  1. scan live data and watch the cam-correlation reading between bank 1 and bank 2 (or between intake-cam-A and exhaust-cam-B on DOHC) — healthy correlation tracks within 1 to 3 crank degrees at any RPM. Wiggle-test the sensor-B harness with the engine running while watching live data for sudden RPM dips, brief stalls, or correlation spikes above 5 degrees.
  2. Backprobe the sensor-B signal wire at the PCM with a scope: a Hall-effect CMP produces a clean 0 to 5 V square wave with edges sharper than 1 microsecond; dropouts to 0 V or noise above 5 V peak-to-peak indicate harness fault.
  3. Verify the 5 V reference at the sensor connector with key-on (should read 4.8 to 5.1 V) and ground side under 0.1 V. Resistance-check the signal wire from sensor to PCM (under 1 ohm) and isolation to chassis ground (over 1 megohm).
  4. Inspect the trigger wheel teeth on the camshaft for damage or for oil sludging that masks the pulses.
  5. Expensive misdiagnosis caveat: intermittent CMP-B codes on Hyundai/Kia Lambda 3.3/3.8L GDI engines and on GM LFX 3.6L V6 are frequently early symptoms of timing-chain stretch — the chain elongates, the cam phaser cannot maintain commanded position, and the cam-correlation drifts out of range; replacing the sensor without measuring chain stretch via OEM scan-tool VVT actuator-test reports a fix that lasts 500 miles before the code returns and the chain finally jumps a tooth.
Vehicle-specific patterns2011-2020 Mopar 3.6L Pentastar V6 (Jeep Wrangler JK/JL, Grand Cherokee, Ram 1500, Charger, Challenger, Pacifica, Durango, 200) throws P0399 from rear…
  • 2011-2020Mopar 3.6L Pentastar V6 (Jeep Wrangler JK/JL, Grand Cherokee, Ram 1500, Charger, Challenger, Pacifica, Durango, 200) throws P0399 from rear-bank CMP wiring degradation along the back of the head and from VVT oil control valve clogging that pulls cam timing out of correlation — the OCV is the cheaper fix and worth ruling out first.
  • 2007-2014Ford 3.5L/3.7L Cyclone V6 (Edge, Flex, Taurus, Explorer, F-150 3.5 EcoBoost shares the architecture, MKZ, MKX, MKS) throws P0399 from the rear-bank cam sensor failing intermittently when heat-soaked.
  • 2008-2017GM LFX/LLT 3.6L V6 (Camaro, CTS, Equinox, Acadia, Traverse, Enclave) throws P0399 from worn timing-chain guides letting the cam phase drift as the chain stretches — this is GM's well-known chain-wear pattern and the fix is a full timing service.
  • 2011-2020Hyundai/Kia Lambda II 3.3L/3.8L GDI (Genesis G80/G90, Sonata, Optima, Cadenza, Telluride, Palisade, Stinger) throws P0399 from oil-starvation cam phaser damage tied to delayed oil changes and from the well-documented Theta/Lambda engine knock-sensor recall scope.

Estimated repair$200 to $1,800.

Look up another code

More free tools

VIN DecoderDecode year, make, model, engine, recalls.Maintenance ScheduleOil, timing belt, fluids, by vehicle.Tire SizeOEM vs new — diameter delta + speedo error.Gas CostWeekly, monthly, annual fuel math.

See all 9 tools