P0342 Code: Camshaft Position Sensor A Circuit Low (Bank 1)

What the P0342 code means

The camshaft position sensor tells the computer the phase of the engine, which means which stroke each cylinder is on. With that information it decides the exact moment for sequential injection and for spark.

Its signal moves inside a limited range, with minimum and maximum values that no real condition can exceed. The P0342 code is stored when the signal drops below that minimum, typically under 0.2 volts for a sustained period.

That rules out mechanical causes right away. A timing offset would produce a P0341, because the signal would be correct but would arrive at the wrong moment. Here the signal simply does not have the level it should, which sends the diagnosis to the circuit: a cut wire, a short to ground, a missing power supply or a sensor that is broken inside.

Most engines can still start without this signal by using a backup strategy based on the crankshaft sensor, which explains why starting takes longer but the vehicle runs. On other models the engine simply will not start.

It helps to know that this sensor works in the harshest conditions on the engine: direct heat from the cylinder head, constant vibration and, in many locations, contact with oil vapor. That combination explains why its wiring ages sooner than the wiring of other sensors and why the insulation hardens until it cracks. When the code appears on a high-mileage vehicle, the harness deserves as much attention as the part.

There is one test that separates the sensor from the wiring without removing anything. With the sensor unplugged and the key on, measure the voltage at the signal pin of the connector. On a Hall effect sensor you should see the reference voltage the computer applies. If there is nothing there, the problem is in the wiring or in the computer itself, and replacing the sensor will change nothing.

P0342 code symptoms

• Check engine light on.
• Long cranking time, several seconds before the engine fires.
• Sudden stalling with a normal restart afterward.
• Loss of power and hesitation when you accelerate.
• Rough idle.
• Higher fuel use.
• On some vehicles, the engine does not start at all.
• No voltage at the signal pin with the sensor unplugged.

Likely causes of the P0342 code

1. Signal circuit cut or shorted to ground.
2. Sensor broken internally, unable to produce a signal.
3. Connector unplugged, corroded or with backed-out pins.
4. Missing power supply on Hall effect sensors.
5. Sensor ground open or with high resistance.
6. Metal shavings stuck to the tip, which weaken the signal.
7. Wiring damaged by heat or rubbing near moving parts.
8. Wrong air gap after fitting a non-specific sensor.
9. Oil on the sensor from a leaking valve cover.
10. Signal wire cut between the connector and the computer, with the sensor itself in perfect condition.

How to diagnose the P0342 code step by step

1. Check whether the engine starts. If it starts with difficulty, the backup strategy is working and you can diagnose it calmly.
2. Remove the sensor and clean its tip of metal shavings and oil. It costs nothing and solves quite a few cases.
3. Check the power supply for the sensor type: 5 or 12 volts on Hall effect sensors, no supply on inductive ones.
4. Measure the resistance of inductive sensors and compare it with the specification.
5. Verify continuity of the signal wire and rule out a short to ground with the computer connector unplugged.
6. Check the sensor ground and its voltage drop.
7. Look at the signal with an oscilloscope while cranking. It should be clean and have enough amplitude.
8. Look for oil in the sensor bore from a leaking valve cover.
9. Measure the voltage at the signal pin with the sensor unplugged. If the reference the computer applies does not show up, the fault is in the wiring and not in the sensor.

How to fix the P0342 code

• Clean the sensor tip and its bore before you consider any replacement.
• Repair the cut or grounded circuit with solder and heat-shrink tubing.
• Replace the sensor with an original or reputable brand part. Generic ones with a different air gap bring the code back.
• Clean or replace the connector and protect it with dielectric grease.
• Restore the circuit ground down to bare metal.
• Fix the valve cover leak if the sensor is soaked in oil.
• Check the air gap after you install the new sensor.
• Repair the signal wire section if the test with the sensor unplugged confirms the computer is not feeding it.

Technical reference data

• Hall effect sensors: 5 or 12 volt supply and a square wave signal switching between high and low values.
• Inductive sensors: AC signal with no external supply, typical resistance of 200 to 1,500 ohms.
• Threshold that sets the code: signal below 0.2 volts for a sustained period.
• Usual air gap between the sensor and the tone wheel: 0.5 to 1.5 millimeters (about 0.020 to 0.060 in).
• P0343 is the opposite code: signal too high.
• With the sensor unplugged, the signal pin should show the computer reference voltage on Hall effect sensors.

Brand-specific notes

Before you order the sensor, take it out and look at the tip. Metal shavings stuck to the magnet and a film of oil from a leaking valve cover are common causes that a rag and five minutes will fix.

If the sensor is soaked in oil, repair the leak too. The new part will be coated again within a few weeks and the P0342 code will come back.

Frequently asked questions about P0342