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P0388 OBD-II Trouble Code: Crankshaft Position Sensor B Circuit High Input

Check Engine Light

P0388 code definition

The P0388 code signifies that there has been a higher than allowed voltage signal from the crankshaft position sensor detected by the car’s computer.

What the P0388 code means

If the crankshaft position sensor sends a higher than allowed voltage signal, the car’s computer will store code P0388. The signal will be about 10% higher than the automaker’s specifications. The Check Engine light will also turn on. However, depending on the vehicle in question, the code may need to be stored up to three times before the Check Engine light turns on to warn the driver of a problem.

What causes the P0388 code?

Several potential causes exist for the P0388 code. These include the following:

  • Damage to the CPS connector
  • Damage to the crankshaft position sensor itself
  • Wiring deterioration due to exposure to engine oil leaks
  • Missing teeth or damaged reductor ring
  • Broken timing belt that damages CPS components

What are the symptoms of the P0388 code?

Symptoms of the P0388 code vary from one situation to another, and from vehicle to vehicle, but they can include the following:

How does a mechanic diagnose the P0388 code?

The first step to diagnose the problem is to connect an OBD II scanner to the car’s computer and read all codes stored. Once this is done, the codes can be cleared and the vehicle test driven to verify the symptoms and determine if the code will reset.

The mechanic should also watch the RPM gauge during cranking and engine operation to determine if it is accurate, or not working. Connecting a scanner can also allow the mechanic to view the RPM signal from the sensor independent of the RPM gauge or when there is no RPM gauge in the vehicle.

The CPS can also be tested directly for reference voltage (outside the vehicle). If it fails, the sensor must be replaced. If the sensor passes, then the problemm is in the wires, wiring harness or connectors. A full visual inspection of all components must be conducted, and any damage must be repaired. The teeth or reductor ring should also be inspected for damage, and replaced if any is noticed.

Once the problem has been repaired, the codes must be cleared again, and the vehicle test driven once more. Note that it may require more than one test drive to set a code.

Common mistakes when diagnosing the P0388 code

One of the more common mistakes here is not inspecting the wiring, wiring harness and connectors prior to replacing the crankshaft position sensor.

How serious is the P0388 code?

The P0388 code is serious, as it has a direct impact on whether the vehicle can be driven. Because this problem can lead to no start situations, it could leave you stranded. Have the problem diagnosed and repaired as soon as possible.

What repairs can fix the P0388 code?

Generally, the most common repair is replacing a damaged or failed crankshaft position sensor. However, wiring problems, corrosion and connector problems are also very common, and must be ruled out before replacing any parts.

Additional comments for consideration regarding the P0388 code

A full diagnosis must be completed to determine the actual cause of the P0388 code. Electrical problems are just as common as failed parts in this situation.

Need help with a P0388 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

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

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