Symptoms of a Bad or Failing Top Dead Center (TDC) Sensor

Schedule Brake Pad Replacement
Service Area

$124.62 - $450.29

Price range for all vehicles
Average rating from 10,920 customers who received a Brake Pads Replacement.

For more than 100 years, the four cycle combustion engine has utilized the same method for creating power. The intake stroke will draw air and fuel into the combustion chamber, the compression stroke will increase cylinder pressure, the power stroke will ignite the air fuel mixture and force the piston down, and finally the exhaust stroke will expel used gases through the tail pipe. However, in order for all the internal components of an engine to work together, there must be a starting point. This is known as Top Dead Center (TDC) and in today's modern engines is monitored by a top dead center sensor.

TDC is often defined as when the first cylinder to fire (usually number one cylinder) has the intake and exhaust valves both closed at the same time. In older engines, TDC was marked on a harmonic balancer as zero degrees and allowed a mechanic to assemble an engine and adjust cylinder head valves to ensure smooth operation. Today's engines are assembled with the same precision, however, the TDC sensor continually monitors the firing sequence of all cylinders. This sensor is vital as today's modern ignition systems are frequently adjusted to variable driving conditions.

When everything works as planned, the TDC sensor should last forever. However, since the sensor is an electrical part, it can fail. Issues such as wear and tear, cracking, and even corrosion can take over and cause a malfunction of the TDC sensor. If a problem exists with this sensor, certain warning signs will alert the driver to a potential problem. Listed below are a few of these indicators that if noticed should inspire you to contact a certified mechanic to inspect, diagnose and replace the TDC sensor if needed.

1. Check Engine Light comes on

The first indicator that a problem with the TDC sensor exists will be that the Check Engine Light comes on. All sensors are monitored by the ECU in any car. When the TDC sensor sends inaccurate information to the ECU, an error code will be created and cause the Check Engine Light to illuminate on the dashboard. Once this occurs, a certified mechanic will need to be called to complete a diagnostic check with a specialized computer that plugs into a port under the dashboard. This will download the error codes and let the mechanic know what area of the vehicle triggered the warning light so they can inspect and repair any damage.

The Check Engine Light is not something that should be ignored. If you see this light on your dash, contact a certified mechanic as soon as possible as it may be a serious problem.

2. Engine will not start

As we described above, the internal combustion motor needs to have a precise ignition timing setting in order for all the cylinders to fire in the correct order and at the right time. If the TDC sensor is damaged, it will not send this information to the onboard computer. As a safety measure, the ECU will shut down the ignition system and you will be unable to start the motor. Depending on the vehicle, the engine will either not crank over or the engine will crank over but not produce a spark. In either case, if your car won't start, contact a mechanic so they can determine why this is happening to you.

3. Engine seems to misfire or runs rough

Another common symptom of a bad or worn out TDC sensor is when the car seems to run rough or the engine misfires. If the TDC sensor is not working properly, the motor usually will shut off quickly to avoid damage to internal components. However, this doesn't always occur. If your motor seems to run rough or sounds like it's misfiring, you should pull the car over to a safe place or head home. Once you arrive home, contact a local mechanic so they can come over to your home or office and inspect the problem.

The top dead center sensor plays a vital role in today's modern engines. This component is commonly used on vehicles manufactured after 1993. If you notice any of the symptoms indicated above, or if the engine of your car just doesn't seem to run happy, contact one of our local ASE Certified mechanics from YourMechanic.


Next Step

Schedule Brake Pad Replacement

The most popular service booked by readers of this article is Brake Pad Replacement. Yourmechanic’s technicians bring the dealership to you by performing this job at your home or office 7 days a week between 7AM-9PM. We currently cover over 10k cities and have 100k+ 5-star reviews... LEARN MORE

SEE PRICING & SCHEDULING

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Recent Brake Pad Replacement reviews

Excellent Rating


YourMechanic Brake Pad Replacement Service

Average Rating

4.9/5

Number of Reviews

10,920

Rating Summary
10,410
326
67
33
84
10,410
326
67
33
84

Bernie

50 years of experience
41 reviews
Bernie
50 years of experience
Honda Accord - Brake Pads Replacement (Rear) - Phoenixville, Pennsylvania
I specifically asked for Bernie to come back, since I was so pleased with the work he did on our other car. This time I got to meet Bernie personally. He is a kind family-man who exhibited the quiet confidence of someone you would expect with the 50 years of automotive experience that he has. I felt very comfortable giving him the key to my car. Two of my kids (ages two and four) came out to greet him, since they remembered him from his first visit. Bernie is great around kids and was very kind to my two-year old son who was trying to "help" Bernie do his job. Thanks again, Bernie!
Honda Odyssey - Brake Pads Replacement (Front, Rear) - Phoenixville, Pennsylvania
I was very pleased with Bernie's work, professionalism, and courteousness. Best brake job I have ever had, and I have had many done (and several done myself, but not on this vehicle). This was a maintenance appointment -- not a repair of something broken -- so I was surprised when the brakes felt so much better after Bernie did the work. You can really see the care he took with our vehicle when I examined everything after he was finished. Thanks, Bernie!

Daniel

9 years of experience
17 reviews
Daniel
9 years of experience
Hyundai Sonata - Brake Pads Replacement (Front, Rear) - Sacramento, California
Awesome customer service. On time and answered my questions with patience. Listened to my concerns and made helpful suggestions. Seemed very knowledgeable and experienced. I will be glad to request him again. Thank you!!

Breck

18 years of experience
532 reviews
Breck
18 years of experience
Toyota RAV4 - Brake Pads Replacement (Rear) - Conroe, Texas
Breck was awesome! He called ahead of time and asked if he could arrive early. He was friendly and easy to talk to. He made me feel comfortable with the service he was going to provide and explained things clearly to me. He smiled and made this experience a good one. I will absolutely be booking future appointments with Breck and I will recommend him and Your Mechanic services to others I know. Thank you!

Brian

19 years of experience
101 reviews
Brian
19 years of experience
BMW Z4 - Brake Pads Replacement (Rear) - Phoenix, Arizona
Brian knows what he is doing and I am so happy yourmechanic.com suggested him for my Z4 car inspection prior to purchasing and even happier he was available to perform my 1st service on the vehicle I purchased. His knowledge on the brand gave him ability to to an in depth inspection and he communicated very well informing me what to prepare for in ownership of my BMW. When he came to perform maintenance on my vehicle he shared so many tips with me. I will absolutely be having Brian come back out when I need future servicing on my car.

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE