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How to Start a Car with a Bad Crankshaft Sensor

Nov 21, 2023      View: 743

 

A malfunctioning crankshaft sensor can bring a vehicle to a standstill, leaving drivers grappling with the challenge of starting the engine. Understanding how to navigate this situation is crucial for those unforeseen moments when a bad crankshaft sensor throws a wrench into the usual starting process. In this guide, we will explore the steps to initiate a car's engine when faced with a faulty crankshaft sensor, offering insights into potential workarounds and precautions to take in such circumstances.

 

What Is a Crankshaft Sensor

A crankshaft sensor, or crankshaft position sensor (CKP), is a vital component in a vehicle's engine management system. To comprehend its function, it's essential to first understand the role of the crankshaft in the engine. The crankshaft serves as a central shaft in the engine, with pistons mounted on it. Located at the lower part of the engine block, the crankshaft rotates as the pistons move up and down during the engine's operation, transmitting power to the transmission.

The CKP sensor plays a crucial role in this process by assisting the powertrain control module (PCM) in monitoring the position and rotation of the crankshaft. This information is instrumental in accurately timing the ignition and fuel injection processes. When the engine experiences irregularities in rotation, the PCM detects and records misfire-related diagnostic trouble codes (DTCs), signaling potential issues.

 

 

The proper functioning of the engine relies heavily on the CKP sensor. Depending on the specific model of the vehicle, the PCM precisely regulates factors such as injection time and length, ignition timing, and occasionally other parameters.

While replacing a faulty crankshaft sensor is a relatively straightforward task, it's essential to address the question of starting a car with a bad crankshaft sensor before proceeding with the replacement. Understanding the steps involved in starting a vehicle under such circumstances is crucial for dealing with the challenges posed by a malfunctioning CKP sensor.

 

How to Start a Car with a Bad Crankshaft Sensor


 

Starting a car with a bad crankshaft position sensor is not advisable, as the sensor plays a crucial role in providing information to the engine control module (ECM) for proper ignition timing and fuel injection. If the crankshaft sensor is malfunctioning, attempting to start the car may lead to various issues, including engine misfires, poor performance, and potential damage.

However, if you find yourself in a situation where you need to move the car temporarily despite a faulty crankshaft sensor, you can try the following steps:

 

Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to check for diagnostic trouble codes stored in the ECM. If a bad crankshaft sensor is causing the issue, you may see a relevant code (e.g., P0335).

Clear the Codes (Temporary Solution): Clearing the codes temporarily might allow the car to start. However, keep in mind that this is not a permanent solution, and the problem will likely recur.

Ensure a Fully Charged Battery: A weak or dead battery can exacerbate starting issues. Ensure that your car's battery is fully charged and in good condition.

Try Starting in Neutral: If you have an automatic transmission, try starting the car in neutral instead of park. Sometimes, a faulty sensor can affect the gear recognition system.

Use Starting Fluid (Gasoline Engines Only): In some cases, using starting fluid in the intake system might help start the engine temporarily. This is not recommended for diesel engines.

 

It's crucial to emphasize that these steps are not a substitute for proper diagnosis and repair. Driving a vehicle with a bad crankshaft sensor can lead to further damage and compromise safety. The recommended course of action is to have the faulty sensor diagnosed and replaced by a qualified mechanic as soon as possible to ensure the proper functioning of the engine.

 

How to Replace the Crankshaft Sensor

1. Stop the car, tighten the handbrake, remove the car key, and disconnect the negative terminal of the battery.

 

2. Use a jack to jack up the left side of the car and place a security bracket under the lower swing arm.

 

3. Place the security bracket base under the lower swing arm.

 

4. Lay out cardboard.

 

 

5. Lie flat and get under the car, and remove the crankshaft position sensor.

 

6. Disassemble the crankshaft position sensor connector.

 

 

7. Clean the crankshaft position sensor, plug and mounting hole.

 

8. Connect the crankshaft position sensor plug and install it in reverse order. (Note: There is an O-ring on it, don’t lose it. If it is replaced, install a new crankshaft position sensor.)

9. First raise the jack, remove the security bracket, then loosen the jack and remove it, and then connect the negative terminal of the battery.

 

10. Insert the car key and let the computer self-check before starting the car.

 

Signs of a Failing Crankshaft Sensor

 

Check Engine Light Illumination

The first indicator of a problematic crankshaft sensor is the illumination of the check engine light. The Engine Control Unit (ECU) or Powertrain Control Module (PCM) triggers this light when it detects irregularities in the engine's health. A malfunctioning crankshaft sensor can provide inaccurate readings to the engine, prompting the check engine light to signal a potential issue.

 

Excessive Engine Vibrations

A properly functioning crankshaft sensor facilitates communication between the crankshaft and the engine, enabling adjustments to compensate for various factors. In the absence of this communication, the engine and crankshaft operate independently, leading to disagreeable speeds and causing noticeable juddering and rattling sensations under the vehicle's hood. These vibrations may vary in intensity and frequency, at times aligning as the crankshaft and engine inadvertently synchronize.

 

Poor Engine Performance

The lack of coordination between the crankshaft and engine due to a faulty sensor results in subpar engine performance. Acceleration may be accompanied by kicking or sputtering as the crankshaft struggles to adapt to increased combustion in the engine. In cases of moderate sensor damage, the vehicle may exhibit slower acceleration than expected given the pressure on the accelerator pedal.

 

Engine Misfiring

Audible signs of a malfunctioning crankshaft sensor include popping and banging sounds during engine startup. The sensor's failure can lead to situations where there is either an excess or insufficient amount of fuel, causing chaotic misfires characterized by loud and abrupt noises.

 

Engine Stalling

Continued driving with a bad crankshaft sensor poses the risk of engine stalling. The probability of stalling increases as the crankshaft and engine fall out of synchronization, hindering the engine's ability to receive the necessary fuel, air, and spark. If the vehicle manages to start, it is likely to stall relatively soon, emphasizing the importance of seeking assistance, such as a tow truck, when dealing with a faulty crankshaft sensor.

 

Final Words

In the realm of automotive troubleshooting, the ability to start a car with a bad crankshaft sensor can be a valuable skill. While the steps outlined in this guide may provide a temporary solution, it is essential to acknowledge that addressing the root cause by replacing or repairing the faulty sensor remains the most effective course of action. A malfunctioning crankshaft sensor not only disrupts the starting process but can lead to a cascade of engine performance issues. Therefore, for long-term reliability and optimal vehicle operation, seeking professional assistance to rectify the underlying problem is strongly recommended.

 

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FAQ

  • How much does it cost to replace a crankshaft sensor?
  • The cost to replace a crankshaft position sensor is around $178 to $238. This cost includes both parts and labor. The labor costs are typically estimated between $96 and $121, while the parts themselves are priced between $82 and $117. It's important to note that these are average estimates, and actual costs can vary depending on various factors such as the make and model of the vehicle, local labor rates, and whether you choose an original equipment manufacturer (OEM) or aftermarket replacement sensor.
  • Does the crankshaft sensor affect the starter?
  • Yes, a faulty crankshaft position sensor can indirectly affect the starter. One of the potential issues associated with a malfunctioning crankshaft position sensor is the misalignment of spark timing during engine cranking. This misalignment can lead to excessively advanced spark timing during cranking, causing higher cylinder pressures and the possibility of a phenomenon known as kick back. Kick back occurs when the combustion process exerts force in the opposite direction of the engine's normal rotation. This force can cause stress on various components, including the starter, starter housing, flywheel or flexplate, and even the engine block where the starter is mounted. Over time, this repeated stress can lead to damage to these components.
  • What code will a bad crankshaft sensor throw?
  • A bad or malfunctioning crankshaft position sensor (CKP sensor) can trigger a specific diagnostic trouble code (DTC) in the onboard diagnostic system. The common code associated with a faulty crankshaft position sensor is P0335. This code is defined as Crankshaft Position Sensor A Circuit Malfunction. When the engine control module (ECM) is unable to detect the proper signals from the crankshaft position sensor, it logs the P0335 code. This code indicates a circuit malfunction related to the CKP sensor, signaling that there may be an issue with the sensor itself, its wiring, or its connections.
  • What kills a crankshaft sensor?
  • The crankshaft position sensor (CPS) is susceptible to various factors that can compromise its functionality. Exposure to excessive engine heat poses a notable risk, potentially causing damage by melting the sensor's protective plastic covering. Additionally, oil or fluid contamination can disrupt the sensor's performance, leading to short circuits or other issues. Mechanical damage, whether from road debris or accidents, can also impact the sensor's integrity. Electrical problems, such as faulty voltage, loose connections, or worn-out wiring, may interfere with the signals transmitted by the CPS. Over time, the natural aging of electronic components and the effects of vibration or shock from rough driving conditions contribute to wear and tear.
  • Can a bad crankshaft sensor ruin an engine?
  • A malfunctioning crankshaft position sensor (CPS) can have significant repercussions on engine performance and reliability. While a bad CPS itself may not directly cause physical damage to the engine, the disruption it introduces to the timing of fuel injection and spark ignition can lead to a host of issues. Engine stalling, difficulty starting, misfires, and rough idling are common symptoms. In addition, the engine's fuel efficiency may suffer, resulting in increased emissions. Ignoring a faulty CPS can potentially exacerbate problems over time, leading to overheating or damage to other engine components.
  • What happens if you keep driving with a bad crankshaft sensor?
  • If you continue to drive a vehicle with a faulty crankshaft position sensor, it may cause the engine to stall or fail to start while driving, affecting the safety and reliability of the vehicle. In addition, a faulty crankshaft position sensor may also cause problems such as reduced fuel efficiency, weakened engine performance, unstable idling, and may even cause engine damage. Therefore, timely detection and repair of crankshaft position sensor problems is key to ensuring normal vehicle operation.
  • How to bypass the crankshaft sensor?
  • Attempting to bypass the crankshaft sensor is not recommended and can lead to various issues with the engine's performance and reliability. The crankshaft sensor plays a crucial role in providing the engine control module (ECM) with information about the crankshaft's position and speed, allowing the ECM to control ignition timing and fuel injection. Bypassing or tampering with the crankshaft sensor can result in incorrect ignition timing, misfires, poor fuel efficiency, and potential damage to the engine. Modern engines rely heavily on the input from sensors like the crankshaft sensor to operate efficiently and meet emission standards. If you suspect an issue with the crankshaft sensor, it's best to address the problem rather than attempting to bypass it.
  • Can a car start without a crank sensor?
  • In most modern vehicles, the Crankshaft Position Sensor (CKP) plays a crucial role in the engine's operation. As you mentioned, the CKP sensor provides information to the engine control module (ECM) about the position and speed of the crankshaft. This information is used to determine the correct timing for fuel injection and spark ignition. If the CKP sensor is faulty or missing, the ECM may not receive the necessary data to properly time the fuel injection and spark, which can result in the engine not starting. In some cases, the engine may crank but not start, or it may not crank at all.