OBD-II Code
P0389
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)
$160–$700
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P0389 means the CKP-B signal is intermittent — present sometimes, gone other times, dropping out for one or more revolutions and then returning.
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.
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.
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.
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.
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 procedureP0389 means the CKP-B signal is intermittent — present sometimes, gone other times, dropping out for one or more revolutions and then returning.
P0389 means the CKP-B signal is intermittent — present sometimes, gone other times, dropping out for one or more revolutions and then returning. This is the hardest of the CKP-B family to diagnose because the fault by definition isn't there when the meter is on it.
Cheapest-first ladder
- attach a scope to the CKP-B signal wire and leave it recording while driving the vehicle through the conditions that throw the code (cold start, hot idle, hard acceleration, going over bumps) — capture a drop-out event in the recording and inspect the waveform at the moment of failure. A clean signal that suddenly disappears for 2-5 revolutions then returns is harness-related (intermittent open or short); a signal that gradually loses amplitude over a minute and then drops is heat-related sensor failure.
- Wiggle-test the harness with the engine idling while watching scan-tool RPM-B — every flicker in the reading corresponds to a physical wire that's broken inside its insulation.
- Hot-soak the engine with a heat gun at the sensor connector and at the PCM connector — if the code throws when one specific connector hits 180 F, that connector is the fault.
- Inspect the reluctor wheel for one chipped tooth that produces an intermittent missed pulse — on the scope this shows as one missing edge per crank revolution and triggers 'intermittent' rather than 'no signal' because the rest of the revolution looks fine. Expensive-misdiagnosis caveat: before replacing the CKP-B sensor for P0389, inspect the harness for chafing at every clip and the connectors for backed-out pins — intermittent codes are 70%+ wiring/connector faults rather than sensor faults, and replacing the sensor on an intermittent leaves the actual fault in place; the code returns within days and the diagnostic clock resets.
Vehicle-specific patterns2002-2014 Subaru EJ-series throws P0389 from the same mounting-boss crack pattern as P0386/P0387 — the sensor walks in its bore intermittently as the…
- 2002-2014Subaru EJ-series throws P0389 from the same mounting-boss crack pattern as P0386/P0387 — the sensor walks in its bore intermittently as the engine flexes under load, causing momentary air-gap excursions.
- 2004-2013Subaru turbo (WRX/STI/Forester XT) sees P0389 especially badly because turbo torque flex amplifies the boss movement.
- 2003-2010Ford 6.0L Powerstroke throws P0389 from connector-pin corrosion at the front-cover sensor that loses contact intermittently under thermal cycling.
- 2001-2010GM Duramax LB7-LMM throws P0389 from a harness chafe point against the engine lift bracket where the insulation wears through and only shorts when the engine torques on the mounts under acceleration.
- 2004-2011Mazda RX-8 secondary back-up sensor throws P0389 from intermittent oil contamination that bridges the sensor element only when the rotor housing is hot.
Estimated repair$160 to $700.
Look up another code
More free tools