P0340 Nissan Altima: Camshaft Position Sensor Circuit Malfunction (Bank 1)

Nissan Altima P0340 Camshaft Sensor Diagnosis

Quick Answer: What is P0340?

On a Nissan Altima, the P0340 code triggers when the Engine Control Module (ECM) loses the signal from the Camshaft Position Sensor. Without this signal, the computer doesn't know the exact position of the engine's valves. In Nissan engines, this is extremely common and is almost always caused by a heat-damaged camshaft sensor.

Safety Warning: A failing camshaft sensor on an Altima will often cause the engine to stall completely while driving at highway speeds without any warning. If your car randomly shuts off and then restarts after cooling down, replace this sensor immediately.

Common Symptoms

Random Stalling: The engine shuts off while driving or idling.
Crank, No Start: The engine turns over but refuses to actually start.
Extended Cranking: It takes 5 to 10 seconds of turning the key before the engine finally catches.
Check Engine Light: Solidly illuminated with code P0340.

Most Likely Causes

Failed Camshaft Sensor (85%): The internal electronics of the sensor degrade due to extreme engine heat (very common in 2.5L engines).
Stretched Timing Chain (10%): If the chain stretches, the camshaft and crankshaft get out of sync, triggering a P0340 or P0011.
Low Engine Oil: The Variable Valve Timing (VVT) system relies on oil pressure. Low oil can throw the camshaft timing off.
Damaged Wiring Harness: Oil leaking from the valve cover can degrade the plastic connector for the sensor.

Detailed Repair Cost Breakdown

Estimates for Nissan Altima (2.5L 4-cylinder and 3.5L V6) in the US market:

Component / Task	Aftermarket Part	OEM Hitachi/Nissan	Labor Time
Camshaft Position Sensor	$35 - $60	$90 - $130	0.5 - 1.0 hr
Crankshaft Sensor (Optional but Recommended)	$35 - $60	$90 - $130	1.0 hr
Connector Pigtail Repair	$20 (Wiring Kit)	N/A	1.0 hr

How to Fix P0340 on a Nissan Altima

1. Buy ONLY OEM Sensors

This is the most important rule for Nissan electronics: Do not buy cheap aftermarket camshaft sensors. Nissan ECMs are highly sensitive and will often reject off-brand sensors right out of the box, leaving you with the exact same P0340 code. Always buy an original Hitachi or Genuine Nissan sensor from the dealership.

2. Replace "The Pair" (Cam & Crank Sensors)

On the Altima 2.5L engine, the Camshaft sensor (top of the engine, rear side) and the Crankshaft sensor (bottom of the engine near the transmission) work in tandem and are identical in design. If the top one has failed due to heat and age, the bottom one is going to fail very soon. Mechanics highly recommend replacing both at the same time to prevent getting stranded.

3. Inspect the Electrical Connector

Before installing the new sensor, look closely at the green or black plastic connector. Because of its location, the valve cover gasket often leaks oil directly onto this plug. If the connector is soaked in oil or the wires are brittle and exposed, a new sensor won't fix the problem. You will need to splice in a new "pigtail" connector.