Fix P0340: Mechanic’s solutions that WORKED

P0340 Camshaft Position Sensor “A” Circuit malfunction means there is an issue with your camshaft position sensor. It can be caused by the sensor and its wiring but also by poorly set timing or faulty ECM.

P0340 quick overview

Meaning	P0340 Camshaft Position Sensor “A” Circuit malfunction
Is it serious?	Monitors the position of the camshaft to make sure the air/fuel inside the cylinder is ignited exactly at right moment for maximum efficiency
What is camshaft sensor?	Monitors the position of the camshaft to make sure the air/fuel inside the cylinder is ignited exactly at the right moment for maximum efficiency
Possible causes	– Faulty camshaft position sensor – Camshaft position sensor wiring problems (e.g., damaged wires or poor connections) – Issues with the timing belt or timing chain – Sensor connector problems – Engine control module (ECM) issues
How to fix	1. Find out if the timing chain/belt wasn’t replaced recently. If it was, the common issue is a wrong installation. 2. Visually check the sensor and connector to see any damages 3. Check battery and alternator voltage with multimeter ———————————————————————– Now either replace the camshaft sensor and hope for the best, but with this code it makes sense to leave it for mechanic if you don’t have experience with engine diagnosing and fixing.
What is timing?	Engine timing make sure that the air/fuel mixture is ignited at the exact right moment when the piston is up in chamber for maximum efficiency. The camshaft which controls air/fuel intake and forcing exhaust gases out of the engine must be in perfect synchronization with cranksahft (outputs power from engine to transmission).

How to fix P0340 – learn from mechanics

I looked into P0340 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Mazda

Vehicle Information:
2004 Mazda 6 S 3.0L
Issue:

• Fault Code: P0340 (Camshaft Position Sensor Circuit Malfunction)
• Vehicle involved in an accident with damage to the valve cover and variable valve timing solenoid.
• Post-repair, the check engine light was on, and the tachometer was not working.

Initial Diagnosis:

• Technician checked timing marks using AllData and Mitchell information.
• Concerns about timing alignment based on the specified positions for the crank and camshafts.

Other Mechanics Suggested:

• Check for a broken wire back to the computer.
• Inspect AC voltage at the CMP sensor during cranking and look for bad connections.

Final Fix:

• The timing chain was installed one tooth off. Re-installing the chain correctly resolved the check engine light, tachometer issue, and P0340 code.

Case #2: BMW

Vehicle Information:
2000 BMW 323i 2.5L
Issue:

• Fault Code: P0340 (Signal Intake Cam Sensor)
• Issues with stalling and MIL (Malfunction Indicator Lamp) light on.

Initial Details:

• Initial diagnosis included three codes related to cam sensors and one for an evap leak at the gas cap.
• Replaced two cam sensors and gas cap, resolving intermittent stalling.
• The car returned two days later with the P0340 code for the intake sensor signal.

Other Mechanics Suggested:

• Use a factory BMW sensor due to potential issues with aftermarket sensors.
• Consider a software update after sensor replacement.
• Verify cam timing, check VANOS values, and ensure proper adjustment of the sensor trigger.

Final Fix:

• The issue was caused by a pin being pushed out of the connector for the intake camshaft position sensor. A new connector resolved the glitches in the scope and the P0340 code.

Case #3: Ford

Vehicle Information:
1999 Ford Explorer XLT 5.0L
Issue:

• Fault Code: P0340 (Cam Sensor Circuit Code)
• Repeated issues with the cam sensor circuit code, even after replacing the cam sensor, synchronization tool, and PCM.

Incident Details:

• The vehicle exhibited a persistent P0340 code and performance issues at highway speeds.
• Despite multiple replacements of the cam sensor and PCM, the code and issues persisted.
• Unplugging the cam sensor while driving resulted in normal engine performance.

Other Mechanics Suggested:

• Use a sync tool during installation to ensure proper alignment.
• Consider the possibility of aftermarket alternators producing excess AC voltage, causing the P0340 code.
• Check for a TSB related to the P0340 code (TSB #02-22-1).

Final Fix:

• The issue was traced to a faulty alternator producing too much voltage, triggering the P0340 code. Replacing the alternator resolved the problem.