OBD-II Code · Sensors
P0343
CMP Sensor A High Input
Severity
high
Left alone, this one tends to take other parts with it.
Can you drive it
Not for long
Driving on this one risks further damage. Get it to a shop rather than carrying on with it.
Indicative cost (USD)
$150–$400
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
CMP voltage high.
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 work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
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
- No start
Likely causes
- Failed sensorMost common
- Wiring short to power
Read the full diagnostic procedureP0343 means the Bank 1 CMP signal voltage is stuck above the high-threshold limit — the signal is pegged at reference voltage with no pulsing, indica…
P0343 means the Bank 1 CMP signal voltage is stuck above the high-threshold limit — the signal is pegged at reference voltage with no pulsing, indicating an open circuit, a sensor with internal open, or a signal wire shorted to a 12V source. The behavior mirrors P0338 on the cam side.
Cheapest-first ladder
- key on engine off, back-probe signal wire at ECM and verify the wire reads the expected reference voltage (typically 5V); then unplug the sensor and verify the signal wire drops toward 0V — if it stays pegged high, you have a short to power upstream of the sensor.
- With sensor plugged in, scope during cranking — a healthy Hall CMP should pulse 0-5V cleanly; a stuck-high signal means the sensor's internal switching transistor is open.
- Inspect the connector pins for backed-out terminals (heat cycling pushes pins out of the housing and breaks contact).
- Check sensor ground continuity to ECM ground — an open ground at the sensor side will present as a stuck-high signal because the pull-up resistor inside the ECM has nothing to pull against.
Vehicle-specific patternsChrysler 3.6 Pentastar sets P0343 when the CMP connector locking tab breaks and the connector backs off slightly under hood vibration — push it on fi…
Chrysler 3.6 Pentastar sets P0343 when the CMP connector locking tab breaks and the connector backs off slightly under hood vibration — push it on firmly and the code clears for 50,000 miles. Ford 5.4 3V triton CMPs fail open from internal connector pin corrosion behind the connector seal. BMW N54/N55 throws P0343 from heat-soaked Vanos sensors and the connector pigtail degrades simultaneously — replace both. Toyota 2GR-FE (Camry, Avalon, Highlander, Sienna 2007-2017) sees occasional P0343 from a recall-related TSB on early production CMP sensors with internal Hall-IC failures.
Estimated repair$140 to $520.
Look up another code
P0343 — frequently asked
What does a P0343 code mean?
CMP voltage high.
What causes a P0343 code?
Common causes: Failed sensor; Wiring short to power.
What are the symptoms of a P0343 code?
Typical symptoms: Check engine light; No start.
Is it safe to drive with a P0343 code?
Not for long. Driving on this one risks further damage. Get it to a shop rather than carrying on with it. Estimated repair: $150-$400.
How do I diagnose a P0343 code?
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. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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