B2478 Code:

OBD-II Diagnostic Body (B) Trouble Code

Possible Cause

The most common causes of this B2478 code being stored are due to a defective input speed sensor or output speed sensor. Other common causes include shorted, open, corroded, or damaged wiring circuits or connectors.

Common Symptoms

  1. A suitable OBD-II scanner (or code reader), a digital volt/ohmmeter, and an oscilloscope will be most helpful in performing a successful diagnosis
  2. If either the reference voltage or ground circuits are open, use the digital volt/ohmmeter to check for continuity (disconnect all related control modules from the circuit before checking circuit resistance or controller damage may occur) and resistance in all circuits
  3. Many scanners will permit the technician to retrieve these alpha numeric numbers (or codes) prior to controller replacement
  4. If the code fails to immediately return, you may have an intermittent condition

Similar Problems

Ignition System Or Misfire
Cruise Control Servo Indicates Low
Kick-Down Switch Failed Short

B2478 Troubleshooting

White smoke means that the fuel that is being injected into the combustion chamber is not being burned properly. The common causes that produce white smoke range from something as simple as low engine compression or water in the fuel to the fuel pump timing being thrown off because something is starving the fuel from getting to the pump in the manner necessary for the pump to time and work correctly. B2478 OBD2 may also be triggered by faults earlier down the line. For example, a dirty MAF sensor might be causing the car to overcompensate in its fuel-trim adjustments. As a result, oxygen sensors are likely to report fuel mixture problems.

How to turn off B2478 check engine light ?

There are two ways to turn off the check engine light:

A repair technician can do so once repairs have been made.
The OBD II can automatically turn it off when it fails to detect the problem after several diagnostic cycles.

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