P0340
Camshaft Position Sensor Circuit Malfunction (Bank 1)P0340 is a generic OBD-II powertrain diagnostic trouble code: Camshaft Position Sensor Circuit Malfunction (Bank 1). 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 P0340 means
P0340 is an SAE generic powertrain code that indicates the Engine Control Module (ECM) has detected an abnormal or absent signal from the Camshaft Position (CMP) Sensor 'A' circuit on Bank 1 (or the single sensor on an inline engine). The CMP sensor monitors a toothed reluctor wheel mounted on the camshaft and sends a variable reluctance or Hall-effect signal to the ECM, which uses it to determine precise camshaft position for sequential fuel injection timing and ignition timing.
When the ECM detects that the CMP signal is missing, erratic, or out of phase with the Crankshaft Position (CKP) sensor signal during cranking or running, it sets P0340 and illuminates the MIL. The fault can be electrical (open circuit, short to ground or voltage, poor connector contact) or mechanical (damaged reluctor ring, incorrect sensor air gap, or timing chain/belt skip causing phase error between CKP and CMP signals).
Driveability impact ranges from hard starting and rough idle to a complete no-start condition, as the ECM may be unable to confirm camshaft phase and therefore cannot correctly sequence injectors or time spark. On variable valve timing (VVT) engines, loss of the CMP signal also disables VVT control, which can noticeably reduce power and increase fuel consumption.
Common causes
Most-frequently reported root causes when P0340 is logged.
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1
Faulty camshaft position sensor (open or shorted internal coil)
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2
Damaged, chafed, or rodent-chewed wiring in the CMP sensor harness
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3
Corroded or loose sensor connector causing intermittent open circuit
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4
Incorrect sensor-to-reluctor air gap (typically requires 0.020"–0.050")
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5
Damaged or missing teeth on the camshaft reluctor wheel
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6
Timing chain or timing belt wear/skip causing CMP signal out of phase with CKP
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7
Failed or weak reluctor ring reference voltage supply or sensor ground
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8
Interference on the signal wire from a faulty alternator or other component (common on Ford applications)
Symptoms drivers notice
How to diagnose P0340
A typical diagnostic flow when this code is present.
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1
Perform a visual inspection of the CMP sensor connector, wiring harness, and sensor body for damage, corrosion, or chafing; repair any visible faults before proceeding
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2
Check for additional DTCs — particularly P0335/P0336 (CKP) or timing-related codes — as concurrent faults may indicate a mechanical timing issue rather than a sensor fault
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3
Measure reference voltage (typically 5 V or 12 V depending on sensor type) and ground integrity at the sensor connector with the ignition on
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4
With the sensor disconnected, measure sensor coil resistance and compare to specification; an open or short reading confirms sensor failure
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5
Perform an oscilloscope or scan-tool live-data check while cranking to verify the CMP signal waveform is present and has adequate amplitude (minimum ~20 mV AC for VR sensors)
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6
Inspect the camshaft reluctor wheel for missing or damaged teeth and verify the sensor air gap is within specification
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7
If wiring, connector, and sensor all test good, inspect timing chain/belt stretch or slippage by comparing CKP vs. CMP phase on a scope; a skipped tooth will produce a consistent phase offset
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
Can I drive with a P0340 code?
Driving is not recommended. While the vehicle may run in some cases, the ECM cannot reliably sequence fuel injection or ignition timing without a valid CMP signal, which can cause stalling, misfires, and potential catalytic converter damage. A no-start condition is also common.
Will clearing the code fix a P0340?
No. Clearing the code removes the stored fault but does not address the underlying electrical or mechanical fault. The code will return as soon as the ECM re-detects the absent or abnormal CMP signal.
Does a new CMP sensor need to be programmed or relearned?
Most CMP sensors are plug-and-play replacements requiring no reprogramming. However, some GM and Chrysler/Stellantis vehicles require a crankshaft position system variation relearn procedure after any sensor or timing component replacement; consult the vehicle-specific service manual.
What is the difference between P0340 and P0341?
P0340 means the ECM detected no signal or a completely absent signal from the CMP sensor 'A' Bank 1 circuit. P0341 means a signal is present but is out of the expected range or correlation with the CKP signal, which more commonly points to a timing chain/belt skip rather than a failed sensor.
Disabling P0340 in software
RaceTune can permanently disable P0340 — 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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