U0027 - FAULT CODE - OBD2

U0027 - LOW SPEED CAN COMMUNICATION BUS (-) SHORTED TO BUS (+)

The Control Area Network (CAN) is a bus standard used in vehicles. Its design allows to interconnect automotive devices without a central computer. An exchange of commands and work data takes place between the devices. Each device contains programmed information about the messages to be exchanged on the serial data circuits.

The CAN bus uses two specific lines for communication, which are called CAN high and CAN low. When the CAN bus is in idle mode, both lines carry 2.5V. During the transmission of data bits, the CAN high line carries 3.75V, and the CAN low line drops to 1.25V. A difference of 2.5V is maintained between both lines. The communication is based on a voltage differential between both lines of the bus since it is not sensitive to electric fields, noise, or inductive peaks.

When the DTC U0027 OBD2 code is set, it is because a periodic supervised message has not been received, which includes that the transmitting device is available.

• Check Engine light ON.

The U0027 OBDII fault code is set for the following reasons:

• Other DTCs may be stored and cause the setting of the U0027.
• Cables or electrical connections of a control module may be damaged.
• A control module may be faulty.

To troubleshoot the U0027 OBD2 diagnostic code, consider this:

• First, consult the Technical Service Bulletins.
• Check with a scan tool if other DTCs are stored next to the code U0027. In this case, diagnose the codes according to the order obtained.
• Check for deficiencies in the wiring and connections of the control modules. Look for conditions created by burn-in or wear, and if such damage is found, make corrections.
• If deficiencies are found in the electrical components of the controllers, one of the controllers could be damaged. However, the diagnosis of the code U0027 is carried out through the vehicle's symptoms.