P0642 - REFERENCE VOLTAGE SENSOR A CIRCUIT LOW

The setting of diagnostic code P0642 OBDII is because the vehicle computer has detected a low voltage reference signal for a particular sensor. This sensor has the designation of A and can be related to the transmission, the housing, or a differential.

Usually, this code is accompanied by another sensor code that specifically indicates which sensor is in trouble. P0642 means that the reference circuit voltage is low. Note that if this code appears alone, it may be due to a PCM programming error. You must first troubleshoot other set codes before diagnosing and repairing the P0642.

• Check Engine light illuminated.
• Problems when the transmission makes changes.
• A transmission malfunction.
• The transfer case for shifting from low to high gear may be difficult.
• The speedometer may not work.

The reasons for setting the error code P0642 OBD2 are

• A defective sensor.
• Short circuits.
• There may be blown or defective fuses.
• The power relay may be in bad condition.

The steps for the diagnosis and correction of the DTC code P0642 OBDII are as follows

• Check with the vehicle's information source for the location of the sensor. Inspect sensor cables and connectors. If faulty wires are present, replace them.
• It uses a digital multimeter to check the reference voltage and ground at the sensor. There should be 5 volts of reference and a good ground connection.
• Tests the resistance and continuity of the sensor. Compare with the readings obtained and the manufacturer's specifications. If they do not match, change the sensor.
• If the sensor's reference voltage is low, use the multimeter to check the resistance and continuity between the sensor and the PCM. Repair short circuits.