How to Start a Car With a Bad Crankshaft Sensor (Step-by-Step)
Updated: Jan 9
An important component that is essential for starting a vehicle is the crankshaft position sensor (CKP).
This sensor plays a vital role in the proper functioning of the engine, as it helps to monitor the position and rotational speed of the crankshaft.
If the crankshaft sensor is not functioning properly, it can cause a range of issues that may make it difficult or impossible to start the car. In this article, we will explore how to start a car with a bad crankshaft sensor.
Table of Contents:
What Is a Crankshaft Position Sensor?
A crankshaft position sensor, also known as a crank sensor, is a device that is used to monitor the position and speed of the crankshaft.
The crankshaft is a central component of an engine, as it converts the linear motion of the pistons into rotational motion, which is then used to power the vehicle.
The crankshaft position sensor is typically located near the crankshaft, and it works by sending electrical signals to the engine control unit (ECU) when the crankshaft is turning.
The engine control unit (ECU) uses this data to regulate the timing of the ignition system, fuel injection, and other engine functions. The crankshaft position sensor, when combined with the camshaft position sensor, enables the engine to be completely in sync and run smoothly.
Where Is the Crank Sensor Located?
The crankshaft position sensor is typically located near the crankshaft, either on the engine block or on the transmission.
In most vehicles, it is located on the engine block, and it is usually located on the front of the engine near the bottom.
Some vehicles may have the sensor located on the transmission, in which case it will typically be found on the side or near the bottom of the transmission.
Signs of a Faulty Crankshaft Sensor
There are several signs of a faulty crankshaft sensor that may indicate that the sensor is not functioning properly. These signs may include the following.
Engine misfiring: If the crankshaft position sensor is not working correctly, it may cause the engine to misfire and run poorly.
Check engine light: The check engine light may come on if the crankshaft sensor is not functioning properly.
Reduced fuel efficiency: A faulty crankshaft position sensor may cause the engine to run poorly, which can lead to reduced fuel efficiency.
Difficulty starting the car: If the crankshaft sensor is not working correctly, it may be difficult or impossible to start the car.
Stalling: If the vehicle has a bad crankshaft sensor the vehicle may unexpectedly stall while driving or idling.
Rough idle: The vehicle may have a rough idle (vibrations, fluctuating RPMs, etc.).
What Happens When a Crank Sensor Goes Bad?
When a crankshaft position sensor goes bad, it can cause a range of issues that may affect the performance of the engine and the ability to start the car.
Because the crankshaft sensor provides vital information to the ECU about the position and speed of the crankshaft, if the crank sensor is faulty it can cause the engine to go out of sync and run poorly, or not run at all.
Some of the potential issues that may occur with a crankshaft sensor failure include the following.
Engine misfiring: If the crankshaft sensor is not functioning properly, it may cause the engine to misfire or run poorly. This can lead to reduced performance and fuel efficiency, as well as increased emissions. This could also lead to engine knocking.
Difficulty starting the car: A faulty crankshaft sensor may make it difficult or impossible to start the car. This is because the sensor is responsible for sending electrical signals to the ECU to indicate the position and speed of the crankshaft, which is necessary for proper ignition timing and fuel injection. Without these signals, the engine may not start or may have starting problems (starts and then quickly stalls).
Damage to the engine: If the crankshaft sensor is not functioning properly, it may cause damage to the engine over time. This is because the sensor is responsible for tracking the speed and location of the crankshaft, ensuring the engine is running in sync. If the sensor goes bad it could result in timing issues and knocking, resulting in engine damage.
Can a Car Start With a Bad Crankshaft Sensor?
In most cases, a car will not start if the crankshaft sensor is not functioning. This is because the sensor is responsible for sending electrical signals to the ECU to indicate the position and speed of the crankshaft, which is necessary for proper ignition timing and fuel injection.
Without these signals, the engine may not start or may start and then quickly stall. However, it is possible that a car may start with a bad crankshaft sensor in certain circumstances.
For example, if the sensor is only partially malfunctioning, it may still be able to provide some signals to the ECU, which may allow the car to start and run for a short period of time.
In these cases, the car may start and then quickly stall, or it may run poorly and experience reduced performance and fuel efficiency.
How to Start a Car With a Bad Crankshaft Sensor
If you are having difficulty starting your car and suspect that the crankshaft sensor may be the cause, there are a few things you can try to get the car started.
You could first try to temporarily fix the crankshaft sensor by following the steps below.
Clear all fault codes using a professional OBD scanner.
Disconnect the negative (ground) terminal on the battery.
Unplug the crankshaft position sensor sensor.
Clean the electrical connectors using electrical contact cleaner.
Wait 15-30 minutes for the ECU to reset.
Plug the crankshaft position sensor back in.
Connect the negative (ground) terminal of the battery.
Start the engine and observe for issues.
These steps may help to temporarily fix the crankshaft position sensor, but they are not a permanent solution and should be followed by replacing the faulty crankshaft sensor as soon as possible.
If those steps did not work, you could try the following to help start a car with a bad crankshaft sensor, these are also not guaranteed to work but they're worth trying.
Check the connections: If the crankshaft sensor is not functioning properly, it may be due to a loose or damaged connection. Check the wiring and connections to the sensor to ensure that they are secure and in good condition.
Clean the sensor: Sometimes, a bad crankshaft sensor may be caused by dirt or debris that has accumulated on the sensor. Use a clean, dry cloth to gently wipe away any dirt or debris that may be blocking the sensor.
Check the fuel levels: If the fuel levels are low, it may be difficult to start the car. Make sure that the fuel tank is at least half full before attempting to start the car.
Check the battery: A dead or weak battery may prevent the car from starting. Check the battery and make sure that it is charged and in good condition.
Try starting the car with a jump start: If the car will not start due to a faulty crankshaft sensor, it may be possible to start the car using a jump start. To do this, you will need to connect the positive and negative terminals of a working car battery to the dead battery using jumper cables.
Try using starting fluid: As a final effort to help the car start you could try using starting fluid, read the instructions on the product you choose. As a general guide you spray it into the intake / air filter for 2-3 seconds while starting the vehicle (cranking it).
If these steps didn't work you'll need to replace the crankshaft sensor with a new one.
How to Fix a Bad Crankshaft Position Sensor
If you have determined that the crankshaft sensor is the cause of the starting issues with your car, it will need to be replaced.
To fix a bad crankshaft sensor, you will need to follow the steps below.
Purchase a replacement crankshaft sensor: You will need to purchase a replacement crankshaft sensor that is compatible with your vehicle. You can find the correct sensor by checking the owner's manual or by consulting a mechanic or a parts store.
Locate the crankshaft sensor: The crankshaft sensor is typically located near the crankshaft, either on the engine block or on the transmission. Refer to your owner's manual or a repair manual to locate the sensor on your specific vehicle.
Disconnect the battery: Before you begin working on the crankshaft sensor, you will need to disconnect the battery negative (ground) terminal to prevent any electrical accidents.
Remove the old crankshaft sensor: Once you have located the crankshaft sensor, you will need to remove it. This is typically done by loosening the bolts or screws that hold the sensor in place, and then gently pulling the sensor out. Be sure to take note of the orientation and position of the old sensor, as the new sensor will need to be installed in the same way.
Install the new crankshaft sensor: Once the old sensor has been removed, you can install the new crankshaft sensor. Make sure to align the sensor with the mounting holes, and then tighten the bolts or screws to secure it in place.
Reconnect the battery: After the new crankshaft sensor has been installed, you can reconnect the battery to the car.
Go for a test drive: Once the battery has been reconnected, you can test drive the car to see if it starts properly. If the car starts and runs smoothly, then the crankshaft sensor has been successfully replaced. If the car still has starting issues, there may be another issue that needs to be addressed.
Note that most vehicles you will need to relearn the crankshaft position sensor using a professional OBD tool (not the usual multipurpose scanner) after replacing it.
What Happens if You Don’t Fix a Bad Crank Sensor?
If you do not fix a bad crankshaft sensor, it can cause a range of issues that may affect the performance and reliability of your car. You could even cause engine damage if you drive a vehicle with a bad crank sensor.
Not fixing a faulty crankshaft sensor could lead to a no-start situation resulting in a breakdown situation.
It may even be illegal to drive with a failing crankshaft sensor due to increased emissions.
Conclusion
A crankshaft position sensor is an important component of a car's engine, as it works with other sensors (such as the camshaft position sensor) to monitor the position and rotational speed of the crankshaft.
If it is not functioning properly, it can cause a range of issues that may make it difficult or impossible to start the car.
If you are having difficulty starting your car and suspect that the crankshaft sensor may be the cause, there are a few steps you can try, such as those listed earlier in this article, on how to start a car with a bad crankshaft sensor.
However, it is important to replace the faulty crankshaft sensor as soon as possible to avoid any further issues or damage to the car. Keeping up with maintenance on your vehicle can help prevent any further issues.