How is fault code U0027 fixed?

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Pull the codes and note anything else stored. U0027 rarely turns up alone. Companion codes like U0100, U0140 or U0155 tell you which modules have gone quiet and point you toward the section of bus that's affected 2. Get the harness up on a lift and follow it by eye and by hand. Look at door grommets, the boot loom, anywhere the wire flexes or rubs. Rodent damage and melted insulation are obvious once you spot them 3. With the battery disconnected, measure resistance between CAN-H and CAN-L. A healthy bus reads around 60 ohms thanks to the two terminating resistors. A reading down near zero or below 5 ohms confirms the lines are shorted together 4. Start unplugging modules one at a time, BCM, door modules, instrument cluster, and re-measure after each. When the resistance jumps back to normal, the last thing you disconnected owns the short 5. Power the system up and check CAN-H and CAN-L voltages. They should sit either side of roughly 2.5V at idle. If both have collapsed onto each other

Low Speed CAN Communication Bus (-) shorted to Bus (+)

Jump to the fix

Severity

Medium

Can I keep driving?

Usually drivable, but get it diagnosed without delay.

First step

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Pull the codes and note anything else stored. U0027 rarely turns up alone. Companion codes like U0100, U0140 or U0155 tell you which modules have gone quiet and point you toward the section of bus that's affected 2. Get the harness up on a lift and follow it by eye and by hand.

UNetwork
0Generic code
0Network / Communication
27Sequence number

What does it mean?

U0027 is a Network (CAN bus, module communications) fault code. It indicates: Low Speed CAN Communication Bus (-) shorted to Bus (+) . This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.

Symptoms

Likely causes

How to fix it

Codes From the Same System

All Fault Codes

Related Similar Codes

This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.