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P0385 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P0385 is an OBD-II Code that refers to Crankshaft Position Sensor B Circuit Malfunction

Meaning

A P0385 code is a general diagnostic trouble code that occurs when the ECM/PCM detects a problem with the crankshaft position sensor B circuit. The crankshaft position sensor B is responsible for monitoring the rotation of the crankshaft and relaying this information to the ECM/PCM. 

When the ECM/PCM detects a problem with the crankshaft position sensor B circuit, it will set a P0385 code and turn on the check engine light.

Causes

Common causes for this code include:

  • Bad crankshaft position sensor
  • Crankshaft position sensor circuit poor electrical connection
  • Crankshaft position sensor harness is open or shorted
  • Faulty starter motor
  • Broken signal plate 
  • Battery is dead or weak 
  • Bad PCM/ECM (rare)

Symptoms

The symptoms of a P0385 code are:

Diagnosis

To diagnose a P0385 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect all the wiring and connectors in the circuit.
  3. Check for battery voltage to the sensor.
  4. Check signal voltage with a test light or voltmeter at the connector while cranking the engine. 
  5. If there is no signal, check for an open or shorted wire between the sensor and PCM.
  6. Check the reference voltage at the PCM connector.
  7. Clear codes and test drive to see if it returns.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P0385 code:

  • Not thoroughly inspecting all the wiring and connectors for damage.
  • Not checking the battery voltage. 
  • Not properly testing the reference voltage at the PCM connector.
  • Clearing codes without properly diagnosing and repairing the underlying cause.

How serious is this?

A P0385 code is a fairly serious code because it can prevent the engine from starting. If the engine is running, it may cause the engine to stall or run poorly.

What repairs can fix the code?

The following are solutions that may fix this problem:

Related codes

A P0385 is related to and may be accompanied by the following codes:

P0386 – Crankshaft Position Sensor B Circuit Range/Performance

P0387 – Crankshaft Position Sensor B Circuit Low Input

P0388  – Crankshaft Position Sensor B Circuit High Input

U0073 – Control Module Communication Bus “A” Off

Conclusion

In conclusion, the P0385 code is a diagnostic trouble code that refers to a problem with the crankshaft position sensor B circuit. The most common cause for this code is a faulty crankshaft position sensor, but it can also be caused by other issues such as a broken signal plate or a starter motor that has failed. Code readers and scan tools are the best way to diagnose this code. Once the code has been diagnosed, the underlying cause can be repaired to fix the problem.