DIYAUTOFIXESMANUALS

Diagnostic Trouble Code Database

P0340Severe (Stop & Fix)

Camshaft Position Sensor 'A' Circuit Malfunction

System:Ignition & Engine Timing•Classification:Powertrain (OBD-II Generic)•Severity Impact:High breakdown risk. Can cause extended engine cranking, loss of power, or total engine stalling.
Direct Technical Definition (Fast Answer)

Code P0340 indicates that the engine computer has lost the electrical signal from the Camshaft Position (CMP) sensor on Bank 1. Without this signal, the computer cannot determine cylinder compression strokes or synchronize sequential fuel injection.

Estimated Repair Time20 – 45 minutes
DIY Parts Cost$25 – $65
Shop Repair Quote$180 – $390
Average DIY Savings$155 – $325
The 80/20 Workshop Rule

Inspect the sensor connector for oil contamination or melted wiring. If wiring is intact, replace the camshaft position sensor with a genuine OEM part (takes 1 bolt on the valve cover).

Estimated DIY Cost
$25 – $65
Tools & DIY parts
Dealership Shop Quote
$180 – $390
Labor ($180/hr) + parts
Net Money Saved
$155 – $325
In your driveway today

Interactive Symptom Pinpoint Troubleshooter

Answer 2 diagnostic tests to isolate the exact component failure for P0340.

DIAGNOSTIC TEST 1 OF 1Step 1

Does the engine experience extended cranking (takes 5-7 seconds to start)?

Live Scanner & Multimeter Benchmark Values

Compare your live OBD-II PID sensor data against OEM factory operating specs for P0340.

Monitored Parameter / Sensor PIDHealthy OEM Operating RangeFault Threshold (Triggers P0340)
Camshaft Sensor Power Pin
11.8V – 14.4V (B+) or 5.0V ref
0V indicates open fuse or broken wire
Sensor Ground Pin
< 0.1V continuity to ground
> 0.3V indicates high ground resistance
Digital Signal Output (Cranking)
0V to 5V clean square wave
Flat line or missing pulse pulses

Symptoms Associated with P0340

Drivers typically observe the following symptoms when the ECM flags P0340:

Extended engine cranking before starting (Long Crank)
Engine dies or stalls unexpectedly while idling
Check Engine Light on
Severe lack of power or vehicle enters Limp Mode

Common Root Causes & Statistical Probability Matrix

Statistical breakdown of what triggers this code based on automotive repair shop data.

Internal failure of the Camshaft Position Sensor
High ProbabilityDifficulty: Easy
Relative Frequency: 75%Estimated Parts Cost: Low
Corroded, oil-soaked, or loose sensor connector plug
Medium ProbabilityDifficulty: Easy
Relative Frequency: 45%Estimated Parts Cost: Low
Stretched timing chain causing phase misalignment
Low ProbabilityDifficulty: Hard
Relative Frequency: 20%Estimated Parts Cost: High

Step-by-Step Diagnostic & Repair Procedure

Follow this logical order to isolate and repair P0340 before spending money on costly parts.

Checklist Progress: 0 of 3 steps complete

Step 1: Inspect Sensor Connector for Oil Ingress

Unplug harness. If engine oil pools inside the plastic pins, replace the sensor.

Step 2: Verify Power and Ground Circuits

Turn Key On, Engine Off: Pin 1 should read 5V or 12V; Pin 2 should have continuity to chassis ground.

Step 3: Replace Sensor (10mm Bolt)

Remove 10mm mounting bolt on valve cover, pull sensor out, lubricate new O-ring with oil, and bolt down.

Vehicle-Specific Failure Trends & Technical Bulletins

Real workshop failure patterns reported by mechanics across popular makes and models for P0340.

Nissan 350Z / Altima / Maxima (VQ35DE)

Common Failure Point:Cam sensors on back of cylinder heads leak oil internally into electronic chip.
Verified Workshop Fix:Replace both Bank 1 and Bank 2 cam sensors with updated metal-angled OEM units ($70 pair).

Ford Mustang / F-150 (4.6L / 5.4L)

Common Failure Point:Alternator bad diode leaks AC ripple voltage into sensor harness, tricking PCM with phantom P0340.
Verified Workshop Fix:Test alternator for AC voltage leak (> 0.5V AC indicates bad alternator diodes).

Chrysler 300 / Dodge Charger (3.5L / 3.6L)

Common Failure Point:Cam sensor magnetic tip attracts microscopic metal fuzz from engine timing chain.
Verified Workshop Fix:Wipe sensor tip clean or install new Mopar sensor.

Dave Miller, ASE Master Tech

ASE L1 Certified Master Reviewer

ASE Certified Master Automobile Technician (A1-A8) & L1 Advanced Engine Performance • 24 years automotive diagnostic experience

“Always verify sensor voltages and harness grounds before purchasing replacement electronic components.”

Editorial review and field diagnostic verification: Updated October 2026

Frequently Asked Questions About P0340

Yes! A weak battery or starter motor that draws excessive amperage can starve the engine computer of voltage during cranking, generating false P0340 codes.