P0340: Camshaft Position Sensor 'A' Circuit (Bank 1)
P0340 means the engine computer is not seeing a normal signal from the camshaft position sensor circuit on bank 1. The most common fix is repairing the sensor wiring or replacing the camshaft position sensor, usually about $120 to $350 at an independent shop.
- Severity
- Moderate
- Can I drive?
- Drive with caution
- DIY?
- Possible with some experience
- Repair cost range
- $100 – $1,800
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What does P0340 mean?
The camshaft position sensor tells the engine computer where the camshaft is so it can time fuel injection and ignition correctly. Bank 1 is the side of the engine with cylinder #1. If the sensor signal drops out, is erratic, or is missing, the computer may not know the camshaft position and can set P0340. The problem may be the sensor itself, damaged wiring, a bad connector, or in some cases a timing issue that throws the signal off.
Common symptoms
- Check engine light on
- Hard starting or no start
- Rough idle
- Stalling
- Poor acceleration
- Engine may run in limp mode
Causes, fixes and costs
P0340: Camshaft Position Sensor 'A' Circuit (Bank 1)
General guide for most cars. Your car may differ.
The engine may stall, run rough, or refuse to start if the signal gets worse. Stop driving if the engine will not stay running, keeps stalling in traffic, or the check engine light starts flashing.
Most likely causes
- 1
Failed camshaft position sensorHigh
A dead or weak sensor often causes hard starting, stalling, rough idle, or an intermittent no-start. If the code returns after being cleared and the wiring looks intact, the sensor is a top suspect.
Quick check: Inspect the sensor for oil damage, heat damage, or cracks, then test or substitute it with a known good part if possible.
- 2
Wiring or connector problemHigh
Broken wires, corrosion, loose pins, or oil in the connector can make the signal cut in and out, which often causes an intermittent check engine light and stalling. Rough running that changes when the harness is moved points here.
Quick check: Wiggle-test the harness with the engine idling, and inspect the connector for bent pins, green corrosion, or damaged insulation.
- 3
Timing chain/belt or cam phaser issueMedium
If the engine has jumped timing or the cam timing is not where the computer expects it to be, the sensor signal may not match crankshaft position. Long cranking, poor power, and multiple cam timing codes make this more likely.
Quick check: Look for related codes such as P0011, P0012, P0014, or P0016, and have cam/crank timing verified.
- 4
Faulty engine control module or reference circuit issueLow
This is less common, but a problem with the 5-volt reference, ground, or the engine computer can mimic a bad sensor. If the sensor and wiring test good but the code keeps returning, this becomes more likely.
Quick check: Measure power, ground, and signal at the sensor and compare with factory specs before replacing modules.
Can you fix it yourself?
Possible with some experience
Difficulty: Moderate. A basic DIY repair may be possible if the sensor is easy to access and you can inspect wiring with a scan tool or multimeter. You will usually need the correct sensor, basic hand tools, and a wiring diagram; if timing is suspected, it is a shop job.
Show the stepsHide the steps
- Scan for other cam/crank timing codes
- Inspect the sensor connector and wiring
- Clear the code and see if it returns right away
- Test the sensor power, ground, and signal if you have a meter
- Replace the sensor if wiring tests good and the sensor is faulty
- Clear codes and road test the vehicle
Estimated repair cost
$120 – $350
Camshaft position sensor replacement: parts about $30-$150, labor about $90-$200
- Camshaft sensor connector or wiring repair$100 – $300
- Timing belt or chain service related to cam timing$700 – $1,800
- Cam/crank signal diagnosis$100 – $200
Prices vary by vehicle, engine layout, and local labor rates.
Frequently asked questions
Can I drive with code P0340?
Sometimes yes, but use caution. If the engine runs rough, stalls, or has a hard no-start, do not keep driving it.
Will P0340 clear itself?
It may go away temporarily if the fault is intermittent, but the code usually comes back until the sensor, wiring, or timing issue is fixed.
Is P0340 always a bad camshaft sensor?
No. A bad sensor is common, but wiring problems, connector corrosion, and cam timing issues can trigger the same code.
How much does it cost to fix P0340?
Most repairs are in the $120 to $350 range for a sensor replacement. If wiring or timing parts are involved, the cost can be higher.
Will P0340 cause a no-start?
Yes, it can. A failed cam sensor or lost cam signal can prevent the engine from starting or make it stall after starting.
Related codes
- P0341 Camshaft Position Sensor 'A' Circuit Range/Performance
- P0344 Camshaft Position Sensor 'A' Circuit Intermittent
- P0016 Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)
- P0335 Crankshaft Position Sensor 'A' Circuit
- P0011 A Camshaft Position - Timing Over-Advanced Or System Performance
- P0012 A Camshaft Position - Timing Over-Retarded
This guide covers most cars and is general advice, not an inspection. Prices are typical US independent-shop ranges and vary by region, car and shop. If your brakes, steering or a warning light feel unsafe, stop driving and contact a mechanic.