The top dead center (TDC) sensor is the point from which the firing order is determined and the ignition system measurements are taken. The measurements are normally defined as before top dead center and after top dead center. The TDC is meant to be a reference point that tells the spark plugs when it should fire and ignite the fuel in the combustion chamber.
The purpose of the TDC sensor is to ensure the reference point on the camshaft is dead center. This is usually located on piston number one. The TDC sensor sends a signal to the engine control module (ECM) which then sends a spark to the piston at top dead center. From here, the fuel is ignited and the power stroke starts as the piston is forced down.
Over time, the sensor can go bad due to becoming old, wearing out, cracking or starting to corrode because of the harsh operating environment. If the sensor goes bad, the engine control module will not receive the correct signal and the spark may be sent to the wrong cylinder at the wrong time. This can cause your vehicle to have issues running, or it may cause the engine to not run at all. Two of the biggest signs your TDC sensor is bad is the Check Engine Light will come on and your vehicle will not start. If this happens, contact a professional mechanic to have your top dead center sensor replaced.
Since the TDC sensor can go bad over time, it is important that you can recognize the symptoms that indicate it needs to be replaced.
Signs that point towards the top dead center sensor going bad include:
- The Check Engine Light comes on
- Your vehicle misfires or runs poorly while idling or driving
- The engine will not run at all, causing you vehicle not to turn on
- Backfiring from the exhaust system
The TDC sensor is important to keeping your engine running smoothly and everything in sync. As soon as you notice any symptoms, it is important to address them immediately.
This article originally appeared on YourMechanic.com as How Long Does a Top Dead Center (TDC) Sensor Last? and was authored by Valerie Johnston.