What does P0340 mean?
The engine control module lost the camshaft position signal — needed for precise fuel injection timing.
Quick Decision Guide
- Failed camshaft position sensor
- Damaged wiring or connector at the CMP sensor
- Timing chain stretch or jump affecting cam position
When to stop driving
If the engine stalls intermittently, stop driving — stalling at speed is dangerous. If it won't start, have it towed. Do not repeatedly crank a no-start condition.
Reviewed by ratchit Automotive Solutions for clarity and inspection-first safety framing. Not a substitute for professional diagnosis.
Repair Decision & Cost Guide
Use this guide to decide what to inspect first, what it may cost, and when to move from DIY checks to professional diagnosis.
P0340 is a clue, not a confirmed diagnosis. Inspect simple causes before replacing parts.
DIY vs. Shop
Can you keep driving?
Best first DIY check
Don't replace this first
When to seek a shop
Recommended next action
Estimated Repair Cost
Inspection cost
$0–$25 DIY scanner
DIY parts cost
$10–$400
Inspect first before replacing parts.
If the vehicle is unsafe to drive, stop driving and seek professional help.
Shop diagnostic cost
$80–$150 (typical shop diagnostic fee)
Shop repair cost
$80–$2,000
Diagnostic uncertainty: This code points to a system or condition, not a guaranteed failed part. Inspect before replacing.
Cost variation: Costs vary by vehicle, location, part quality, labor rate, and the confirmed root cause.
Inspect Before Replacing
These checks are cheap, fast, and rule out the most common causes before spending money on parts.
- 1Inspect the CMP sensor connector for oil, corrosion, or damaged pins.
- 2Check for companion CKP codes (P0335) — both sensors failing together can indicate timing chain issues.
Track this ignition/timing issue
Save this issue to My Garage, track what you inspect, and build service history for this vehicle.
V-IQ readiness preview: High impact — resolving and tracking this issue may noticeably improve your V-IQ readiness. Tracking active codes and resolutions builds a service history we use to estimate V-IQ readiness over time.
Understanding P0340 in detail
The camshaft position sensor (CMP) works alongside the crankshaft position sensor to provide the ECM with cylinder identification and valve timing information. While the CKP sensor tells the ECM where the crankshaft is in its rotation, the CMP sensor identifies which cylinder is on its compression stroke, enabling sequential fuel injection. When the CMP signal is lost, many vehicles will fall back to a less efficient batch-fire injection mode, causing rough running and reduced power. Some vehicles — particularly those that rely heavily on the CMP for ignition timing — may stall or refuse to start entirely. Like the CKP sensor, the CMP is an electromagnetic device that degrades with heat and age, and its connector is a common failure point due to environmental exposure.
Symptoms of P0340
- Check engine light on
- Engine stalls or has difficulty starting
- Rough running or misfires
- Reduced power
- Extended cranking time before starting
Common causes
- Failed camshaft position sensor
- Damaged wiring or connector at the CMP sensor
- Timing chain stretch or jump affecting cam position
- Oil contamination at the sensor (on sensors mounted inside the engine)
How to diagnose P0340
Steps ordered by urgency — tackle Now items first.
- NowInspect the CMP sensor connector for oil, corrosion, or damaged pins.
- NowCheck for companion CKP codes (P0335) — both sensors failing together can indicate timing chain issues.
- SoonTest CMP sensor resistance and signal output during cranking with a multimeter or scanner.
- LaterIf sensor tests good, evaluate timing chain condition — chain stretch can produce erratic CMP signals.
How to fix P0340
Fixes listed in order of likelihood and cost-efficiency.
- 1Replace camshaft position sensor
- 2Repair CMP wiring or connector
- 3Replace timing chain if stretched
Want to check your full vehicle?
Run a free maintenance scan to see what else needs attention based on your year, make, model, mileage, and climate.
Recommended tools & parts
These recommendations appear because this issue commonly requires inspection in this system area. ratchit does not recommend replacing parts until the likely cause is confirmed.
Sensor & Diagnostic Kit
Test and replace common engine sensors — O2, MAF, cam/crank
Check sensor behavior before replacing parts Verify fitment for your year/make/model.
Ignition & Misfire Inspection Kit
Inspect spark plugs, coils, and ignition components before replacing parts
Inspect spark plugs, coils, and misfire causes before buying parts Verify fitment for your year/make/model.
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Estimated Repair Cost — P0340
Ranges vary by vehicle, region, and shop. Use as a ballpark — always get a quote.
DIY estimate
$20 – $60
Shop estimate
$80 – $250
DIY estimate
$10 – $40
Shop estimate
$80 – $200
DIY estimate
$200 – $400
Shop estimate
$800 – $2,000
Cost data is estimated and may not reflect your specific vehicle or location.
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Frequently Asked Questions
Track this ignition/timing issue — track what you inspect and build service history for this vehicle.
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