U0015: Medium Speed CAN Communication Bus (-) Shorted to Bus (+)

What it means

A short between the positive and negative lines of the medium-speed CAN communication bus has been detected. The affected functions depend on the vehicle network layout.

At a glance

• Usually lights the warning light of the system that lost communication

How it works

The medium-speed CAN bus communicates over the CAN-H and CAN-L signal pair. U0015 indicates those two wires are shorted together, disrupting messages on the affected network; damaged termination can also impair signaling and should be assessed when the wiring pair is intact.

Common causes

Most likely first.

1. CAN-H/CAN-L harness short
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan all modules and save freeze-frame data and communication codes to identify which MS-CAN nodes were lost when the fault occurred.
2. Inspect the medium-speed CAN pair, especially recently disturbed body harness sections, for pinching, crushed insulation, or connector pins bridging CAN-H and CAN-L.
3. With the vehicle powered down as specified by the manufacturer, check for an unintended connection between CAN-H and CAN-L and compare with the manufacturer's specification.
4. Inspect connector terminals and repairs for conductive contamination or incorrect splicing across the paired wires.
5. Use the manufacturer's branch isolation procedure to find the harness section or module connector where the two lines are connected.
6. Check termination only by the manufacturer's procedure after confirming the CAN-H/CAN-L pair is not shorted.

Common fixes

• Repair CAN-H and CAN-L wires shorted together by damaged insulation.
• Replace a pinched section of the medium-speed CAN harness.
• Repair connector pins or contamination bridging the CAN pair.
• Replace a module only if testing confirms an internal short between its CAN lines.
• Repair a confirmed termination fault if the isolated CAN pair and modules test correctly.

Can I keep driving?

If only nonessential body or comfort features are affected and essential controls work normally, keep any driving cautious and limited. Stop if safety-related functions are impaired, because the short can disrupt communication among multiple modules.