B3872 Code:

OBD-II Diagnostic Body (B) Trouble Code

Possible Cause

The most common cause for this B3872 type of failure is due to liquids spilled on the upshift/downshift switch. Open or shorted electrical wiring, damaged, corroded, or disconnected wiring or connectors are also a viable possibility.

Common Symptoms

  1. Typical resistance for this sensor should be approximately 150 ohms but double check manufacturer's specifications prior to testing
  2. This signal is systematically forwarded to affected control modules that utilize the data to accomplish various other tasks
  3. If the initial resistance is within specifications, leave the leads of the digital volt/ohmmeter connected and heat the resistor with a heat gun
  4. As exhaust temperature decreases (with the engine off), circuit resistance increases and the feedback voltage signal to the PCM decreases

Similar Problems

Computer And Auxiliary Outputs
Cruise Control Servo Indicates Low
Cruise Control System - Vehicle Accel Too High

B3872 Troubleshooting

If there is a clicking noise when you attempt to start the engine and the engine does not crank, it typically means there is something wrong with the battery, such as a low or discharged battery or corroded or loose battery cables. If the engine cranks when you attempt to start the car, but fails to turn over, this may mean there is a problem with the fuel or ignition. Other common reasons an engine may fail to start include a failure of the starter motor relay, a clogged fuel filter, a defective fuel pump or an ignition switch failure. B3872 the main thing to check is to verify the operation of the VCT solenoid. You're looking for a sticking or stuck VCt solenoid valve caused by contamination. Refer to vehicle specific repair manual to perform component tests for the VCT unit.

How to turn off B3872 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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