P0340
Camshaft Position Sensor A Circuit Malfunction
Your engine computer cannot correctly read the camshaft position sensor on bank 1, or the only cam sensor on the engine. This can cause hard starting, rough running, stalling, or a no-start condition. The problem may be the sensor, its wiring, connector, timing issue, or sometimes the crankshaft sensor.
- SEV
- 4/5
- DRIVE
- CAUTION
- DIY
- $25–$180
- SHOP
- $120–$550
Quick answer
AI-CITATION READYWhat it means
Can you drive with it?
Most common causes
- Failed camshaft position sensor
- Damaged, loose, oil-soaked, or corroded camshaft sensor wiring or connector
- Faulty crankshaft position sensor causing synchronization errors
Typical repair cost
DIY usually runs $25–$180. Typical shop repair lands around $120–$550, depending on the root cause.
01 / Definition
P0340 sets when the powertrain control module detects an invalid, missing, or out-of-range signal from the camshaft position sensor A circuit on bank 1 or the single sensor used by the engine. The PCM uses this signal along with the crankshaft position sensor to determine valve timing, injector timing, and ignition synchronization. A fault can be caused by the sensor itself, the wiring or connector, low reference voltage, poor ground, or mechanical timing problems.
02 / Drive status
With caution. If the engine starts and runs, drive only short distances because stalling, poor performance, or a no-start can happen without warning. If the engine is hard to start, runs very poorly, or stalls, do not continue driving until it is diagnosed.
03 / Symptoms
- Check engine light on
- Hard starting
- Long crank before starting
- Engine cranks but will not start
- Rough idle
- Engine stalling
- Misfires
- Poor acceleration
- Reduced fuel economy
04 / Causes
| 1 | Failed camshaft position sensor | high |
|---|---|---|
| 2 | Damaged, loose, oil-soaked, or corroded camshaft sensor wiring or connector | high |
| 3 | Faulty crankshaft position sensor causing synchronization errors | medium |
| 4 | Timing chain or timing belt stretched, jumped, or installed incorrectly | medium |
| 5 | Poor sensor ground or missing 5-volt reference from the PCM | medium |
| 6 | Damaged reluctor wheel or tone ring on the camshaft | low |
| 7 | Low battery voltage affecting sensor signal during cranking | low |
| 8 | PCM failure | low |
05 / Diagnostic sequence
- 01Confirm P0340 with a scan tool and check for related codes such as crankshaft sensor, timing, or misfire codes.
- 02Inspect the camshaft position sensor connector and wiring for broken insulation, oil contamination, corrosion, loose pins, or rubbing near the engine.
- 03Check battery voltage and charging system condition, especially if the code appears during cranking or after a low-battery event.
- 04Use live data to verify camshaft RPM or synchronization signal while cranking and running, and compare with crankshaft signal if available.
- 05Test the camshaft position sensor power supply, ground, and signal circuit with a multimeter or oscilloscope according to service information.
- 06Check for proper 5-volt reference and a solid ground at the sensor connector.
- 07If the sensor and wiring test good, inspect mechanical timing for a stretched or jumped timing chain or belt.
- 08Inspect the camshaft reluctor or tone wheel for damage or misalignment if accessible.
- 09Clear the code and road test after repair to confirm the fault does not return.
06 / Repairs
| 1 | Repair or replace damaged camshaft position sensor wiring, connector, or terminals | $10–$150 |
|---|---|---|
| 2 | Replace the camshaft position sensor | $25–$180 |
| 3 | Replace the crankshaft position sensor if testing shows loss of synchronization from that sensor | $30–$200 |
| 4 | Correct low battery voltage or charging system problems affecting sensor operation | $0–$250 |
| 5 | Repair timing chain or timing belt issues and set engine timing correctly | $300–$1500 |
| 6 | Replace damaged camshaft reluctor or tone wheel if equipped separately | $150–$800 |
| 7 | Replace or reprogram the PCM only after all sensor, wiring, and timing tests pass | $500–$1500 |
07 / Related codes
08 / FAQ
Can a bad camshaft position sensor cause a no-start?
Yes. On many engines, a failed camshaft position sensor or its circuit can prevent the engine from starting or cause a very long crank time.
Can I just replace the camshaft sensor for P0340?
Sometimes that fixes it, but not always. Wiring problems, timing chain issues, connector damage, or a bad crankshaft sensor can also trigger P0340.
Is P0340 serious?
Yes. The engine may stall, run poorly, or fail to start, so it should be diagnosed soon.
What is bank 1 or single sensor?
Bank 1 is the side of a V-type engine with cylinder 1. On inline engines, the code usually refers to the engine's only camshaft position sensor circuit or the primary cam sensor.
Will low battery voltage cause P0340?
It can, especially during cranking. Low voltage can weaken or distort the sensor signal and cause the PCM to lose synchronization.
09 / Source and method
- DATA BASIS
- OBD-II REFERENCE + OBD2.HELP
- METHOD
- STATIC VALIDATION
- SAFETY
- INFORMATIONAL
This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.
Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.
Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.