What causes a camshaft position sensor to go out?
The sensor usually fails due to electrical faults, contamination, heat, or timing-related wear. When it goes out, the engine may stall, misfire, or fail to start altogether.
Camshaft position sensors (CPS) monitor the position of the camshaft so the engine control module can synchronize fuel injection and ignition. Problems with the CPS can be intermittent or permanent, and they often trigger diagnostic trouble codes such as cam position sensor circuit malfunctions. Understanding the common causes helps diagnose and fix the issue more quickly.
Common causes of camshaft position sensor failure
The following are frequent drivers of CPS failure across a wide range of vehicles. Note that some failures stem from electrical health, while others arise from mechanical changes in the engine timing apparatus.
Electrical and wiring issues
- Damaged wiring harness or frayed insulation from heat, vibration, or contact with moving parts.
- Loose, corroded, or dirty electrical connectors and poor grounding, which disrupt the sensor signal.
- Faulty or degraded power supply and 5V reference provided by the engine control unit (ECU) or PCM.
- Short circuits or open circuits within the sensor circuit, causing intermittent or no signal.
Electrical problems can produce erratic readings or complete loss of signal, often accompanied by check engine light codes such as cam position sensor circuit faults.
Mechanical and timing issues
- Oil leaks or contamination reaching the sensor or the reluctor/tone wheel, damping the signal or causing shorts.
- Sensor overheating due to excessive engine temperatures or poor cooling, accelerating component wear.
- Damage to the reluctor ring or misalignment of the tone wheel, which distorts or blocks the signal.
- Timing belt/chain wear, slack, or misalignment that alters the relationship between the camshaft and crankshaft, leading to incorrect signal timing.
- Aging or failing CPS itself, especially in older vehicles, as electronic components drift over time.
Mechanical or timing-related problems typically produce a timing mismatch or sporadic signal, which can cause misfires, rough idle, or no-start conditions even if the wiring is intact.
How to diagnose a faulty camshaft position sensor
Diagnosing CPS problems involves scanning codes, inspecting wiring, and testing the sensor’s electrical performance. The following steps reflect common automotive practice, but vehicle-specific procedures may vary.
- Scan the vehicle’s onboard computer for codes related to cam position or sensor circuits (for example, cam position sensor circuit faults or P0340-class codes).
- Visually inspect wiring harnesses and connectors for damage, corrosion, or loose pins.
- Test the sensor’s power and signal using a multimeter or oscilloscope, verifying a stable 5V reference, a solid ground, and a clean signal waveform.
- Check the reluctor ring or tone wheel for cracks, missing teeth, or misalignment with the sensor.
- Look for oil leaks or contamination near the sensor and surrounding timing components that could affect operation.
- Consider substituting a known-good sensor to determine whether the fault follows the part or remains with the system wiring/ECU.
Diagnosing CPS faults often requires careful interpretation of codes alongside live waveform analysis. If the fault persists after wiring and sensor checks, the ECU or related sensors may be involved and warrant professional assessment.
What to do if you suspect a camshaft position sensor problem
If symptoms suggest a CPS issue, here are practical steps to take. This guidance emphasizes safety and proper diagnosis to avoid unnecessary part replacements.
- Arrange a diagnostic with a qualified mechanic who can perform targeted electrical tests and waveform analysis.
- Use reputable or original equipment manufacturer (OEM) parts when replacing the sensor to ensure compatibility and longevity.
- Repair any oil leaks or cooling problems that could contaminate or overheat the sensor area to prevent repeat failures.
Closing note: Replacing a faulty CPS is common maintenance, but addressing wiring integrity and timing system health is essential to prevent recurrence and ensure reliable engine operation.
Summary
Camshaft position sensor failures arise from electrical wiring problems, connector issues, oil or coolant contamination, heat stress, and timing-related mechanical changes. A structured diagnosis—covering codes, wiring, sensor performance, and timing components—helps pinpoint the root cause and guide effective repairs. Timely attention can restore proper engine timing and prevent more extensive damage.
Why would a camshaft position sensor go bad?
Repeated camshaft position sensor faults can stem from wiring issues, connector corrosion, or vacuum leaks near the sensor. Inspect the plastic elbow connecting the rubber tube to the air intake cowling for cracks, as leaks here disrupt airflow readings, triggering sensor codes.
Can I drive my car with a bad camshaft position sensor?
No, you should not drive your car with a bad camshaft position sensor, as it can cause poor engine performance, potential stalling, and may lead to more significant and costly engine damage. Driving with this issue can lead to unexpected stalling, rough idling, misfires, and a lack of power, which increases the risk of an accident. It's best to get the sensor replaced as soon as possible.
Risks of driving with a bad camshaft position sensor
This video explains the risks of driving with a bad camshaft position sensor: 59sAuto Repair GuysYouTube · Jul 23, 2022
- Stalling: The engine may unexpectedly shut off, especially while slowing down, which can cause an accident, particularly if you lose power brakes and steering.
- Poor performance: You may experience a rough idle, misfires, poor acceleration, and reduced power.
- Engine damage: Unburnt fuel can enter the exhaust and damage the catalytic converter or other components. In some cases, backfires can cause jump timing chains, which can lead to catastrophic engine failure.
- Fuel inefficiency: The engine will run less efficiently, leading to increased fuel consumption.
- Starting issues: The car may become difficult to start or take longer to start.
What you should do
- Get it replaced: The safest and most recommended action is to have the sensor replaced promptly by a qualified mechanic.
- If you must drive: If you absolutely need to drive a very short distance, do so with extreme caution. Be prepared for the engine to stall, and be mindful that this is a temporary solution at best and will not prevent future problems.
What are the three common causes of sensor failure?
These faults can arise from various issues, such as physical damage, electrical problems, environmental factors, or software errors. A faulty sensor cannot perform its function properly but instead may provide false information for decisions, thus making the system unreliable.
What is the life expectancy of a camshaft position sensor?
Camshaft position sensors are designed to last the life of the vehicle, often going 100,000 miles or more without needing replacement. However, they can fail prematurely due to heat damage, internal shorts, or mechanical issues, and are typically replaced only when they fail, not on a set maintenance schedule.
- Typical lifespan: Many sensors will last for the lifetime of the car, which can be hundreds of thousands of miles.
- Replacement is not routine: Unlike parts like oil filters or brake pads, camshaft position sensors don't have a regular replacement interval.
- Reasons for failure: They are exposed to engine heat, which can degrade electrical components over time. Other causes of failure include internal shorts, mechanical damage, or a broken encoder wheel.
- Symptoms of failure: When a sensor fails, it can cause issues such as a "Check Engine" light, poor acceleration, engine misfires, and difficulty starting or idling.
