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Live data is essential for P0340 diagnosis. P0340 with live data shows cam timing vs crank timing correlation. A Bluetooth OBD2 scanner showing both CKP and CMP signal data lets you distinguish a sensor failure from a timing chain issue - a critical difference for repair cost. See top-rated scanners on Amazon ↗
🗺️ Where Is the Problem?
Blueprint view - P0340 fault at camshaft position sensor on cylinder head; ECM loses cam timing reference needed for sequential fuel injection
These are statistical causes across ALL vehicles - your exact car may rank differently
For example, on a Honda 4-cyl the downstream O2 sensor causes P0340 64% of the time, but on a GM 5.3L V8 the catalytic converter is the cause 71% of the time. Get a probability ranking built specifically for your year, make, model, and mileage.
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🎯 Top Causes & Probability
58%
#1 - Most Likely
Failed Camshaft Position Sensor
The CMP sensor has failed internally. Engine may start but run rough, or crank without starting.
Estimated Cost
$80–$300
Repair Type
DIY
25%
#2 - Check First
Damaged Wiring or Connector
Open circuit or short in the 3-wire sensor harness. The signal wire is most vulnerable in high-heat locations.
Estimated Cost
$50–$250
Repair Type
DIY/Shop
12%
#3 - Less Common
Stretched Timing Chain or Worn Tensioner
If the chain has jumped a tooth or stretched, the cam timing shifts enough to trigger this code. Requires timing chain replacement.
Estimated Cost
$400–$1,500
Repair Type
Shop
5%
#4 -
Damaged Reluctor Ring on Camshaft
Chipped or missing teeth on the cam's reluctor wheel cause signal dropout.
Estimated Cost
$200–$600
Repair Type
Shop
🔧 Step-by-Step Diagnosis
- Check for other codes - If P0016 or P0017 are also present, this is a timing chain issue, not just a sensor. Address those codes first before replacing the CMP sensor.
- Inspect the sensor and connector - Locate the CMP sensor (typically at the front of the cylinder head) and inspect the connector for corrosion, backed-out pins, or heat damage.
🚗 Most Affected Vehicles
📍 Find a Trusted Shop Near You
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Tips for Choosing a Shop
- Ask if they charge a diagnostic fee and whether it applies toward the repair
- Request a written estimate before approving any work
- Ask specifically about the part brand - OEM vs. aftermarket matters for this code
- Check Google reviews for recent mentions of the specific repair you need