Failed camshaft position sensor. Wire or connector in the sensor circuit shorted, grounded, broken, corroded or chafed. Open circuit in the sensor wiring. Failed crankshaft position sensor. Engine misfire (listed by RepairPal). Failed engine computer (PCM), which is less common (listed by OBD-Codes.com).

Repair or replace damaged circuit wiring or connectors. Replace the camshaft position sensor if testing shows it has failed. Diagnose and replace the crankshaft position sensor if it's the real cause. Fix any underlying misfire. Diagnose and replace the PCM only after the sensor and wiring check out.

P0340🔧 Engine timing / cam and crank sensorsStop and fix promptly

P0340: Camshaft Position Sensor A Circuit (Meaning, Causes, Fixes)

Q: What does P0340 mean?

P0340 means the engine computer isn't getting a usable signal from camshaft position sensor 'A'. Because the code covers the whole circuit, the cause can be the sensor, its wiring or connector, the crankshaft position sensor, or (less often) the engine computer itself, so don't just replace the cam sensor and hope. The camshaft position sensor (CMP) reads the exact rotational position of the camshaft. RepairPal explains that the engine computer (PCM) uses this signal to time ignition spark and fuel injection, and sets P0340 when the signal is irregular, interrupted or missing. P0340 is a generic code that applies to all 1996-and-newer OBD-II vehicles, and on V-type engines 'A' usually refers to the Bank 1 sensor. OBD-Codes.com stresses that the word 'circuit' means the fault can be anywhere in the circuit: the sensor, the wiring, or the PCM. The two sources agree on the core causes but differ in emphasis: OBD-Codes.com includes a failed PCM and an open circuit in its list, while RepairPal adds that a misfiring engine can trigger the code and warns that the cam sensor is often replaced when the real cause is a bad crankshaft sensor, chafed wiring or a misfire. RepairPal also notes that in many cases there are no noticeable symptoms. P0340 ranked 19th in the 2026 carfaultcodes.co.uk review of UK fault code data.

Q: Can I keep driving with P0340?

Stop and fix promptly. Get this diagnosed promptly. RepairPal rates P0340 'Urgent' and lists stalling and an engine that dies and won't restart among the symptoms. If the engine hesitates, stalls or is hard to start, avoid relying on the car, especially in traffic or on the highway, until it's checked.

Reviewed 2026-10-22 · Based on 3 cited source(s)

What P0340 means

The camshaft position sensor (CMP) reads the exact rotational position of the camshaft. RepairPal explains that the engine computer (PCM) uses this signal to time ignition spark and fuel injection, and sets P0340 when the signal is irregular, interrupted or missing. P0340 is a generic code that applies to all 1996-and-newer OBD-II vehicles, and on V-type engines 'A' usually refers to the Bank 1 sensor. OBD-Codes.com stresses that the word 'circuit' means the fault can be anywhere in the circuit: the sensor, the wiring, or the PCM. The two sources agree on the core causes but differ in emphasis: OBD-Codes.com includes a failed PCM and an open circuit in its list, while RepairPal adds that a misfiring engine can trigger the code and warns that the cam sensor is often replaced when the real cause is a bad crankshaft sensor, chafed wiring or a misfire. RepairPal also notes that in many cases there are no noticeable symptoms. P0340 ranked 19th in the 2026 carfaultcodes.co.uk review of UK fault code data.

Severity: can I keep driving?

Stop and fix promptly

Get this diagnosed promptly. RepairPal rates P0340 'Urgent' and lists stalling and an engine that dies and won't restart among the symptoms. If the engine hesitates, stalls or is hard to start, avoid relying on the car, especially in traffic or on the highway, until it's checked.

Common symptoms

Check engine light on
Hard starting, or cranking without starting
Engine hesitation or stalling (listed by RepairPal)
Engine dies and won't restart (listed by RepairPal)
Rough running or misfiring
Loss of engine power (listed by OBD-Codes.com)
Sometimes no noticeable symptoms at all (noted by RepairPal)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Failed camshaft position sensor
Wire or connector in the sensor circuit shorted, grounded, broken, corroded or chafed
Open circuit in the sensor wiring
Failed crankshaft position sensor
Engine misfire (listed by RepairPal)
Failed engine computer (PCM), which is less common (listed by OBD-Codes.com)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Read all stored codes. A crankshaft sensor code (such as P0335) or misfire codes (P0300 to P0304) alongside P0340 change where you should look first.
Visually inspect the camshaft sensor connector and wiring for corrosion, loose pins, chafing or broken wires, and repair anything damaged.
If you have a multimeter and the service information for your vehicle, check the wiring for continuity and the sensor for its specified supply and signal voltage, as OBD-Codes.com suggests.
Clear the code after any repair and see whether it returns before buying parts.

Typical fixes

Repair or replace damaged circuit wiring or connectors
Replace the camshaft position sensor if testing shows it has failed
Diagnose and replace the crankshaft position sensor if it's the real cause
Fix any underlying misfire
Diagnose and replace the PCM only after the sensor and wiring check out

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

The engine cranks but won't start, or stalls while driving
You've replaced the cam sensor and the code came back, which RepairPal flags as a common misdiagnosis
Testing the sensor signal properly needs wiring diagrams and often an oscilloscope
A PCM fault is suspected

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Will a new camshaft sensor fix P0340?

Not necessarily. Both sources warn that the code covers the whole circuit. RepairPal lists replacing the cam sensor when the real cause is a bad crankshaft sensor, poor connection, chafed wiring or a misfire as common misdiagnoses.

Can I drive with P0340?

RepairPal rates it 'Urgent', and the engine may hesitate, stall, or die and not restart. Some cars show no symptoms, but have it diagnosed promptly rather than risk stalling in traffic.

What's the difference between P0340 and P0341?

P0340 is a general circuit fault for camshaft sensor 'A', meaning the signal is missing or irregular. P0341 is the range/performance code for the same sensor, meaning a signal is present but doesn't look right.

Sources

Last reviewed 2026-10-22. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.