C1605 — CAN Hardware Error | CAN Bus OFF

Causes

• Damaged or shorted CAN-H/CAN-L wiring
• Open or corroded connector(s) at CAN nodes or junctions
• Failed CAN transceiver or ECU (module)
• Incorrect or missing termination resistor(s)
• Low battery/unstable supply or blown fuse to CAN transceiver power/ground
• Water intrusion or corrosion in harness or control modules

Symptoms

• Multiple modules reporting loss of communication or lamp illumination (warning lights)
• Intermittent or complete loss of functions controlled by bus (ABS, BCM, engine, transmission, etc.)
• Stored CAN-related codes across multiple modules
• No network traffic seen on scan tool or bus rapidly switching between active traffic and bus-off
• Vehicle may limp or fail to start if powertrain modules are isolated

What to check

• Read all modules with a capable scan tool — note related U or C codes and which modules are offline
• Record live CAN bus status (Bus-Off flags, error counters) from the affected module(s) if available
• Inspect battery voltage and grounding points; verify proper supply to all CAN nodes and fuses
• Visually inspect CAN wiring, connectors, and junction boxes for damage, corrosion, water ingress, or aftermarket taps
• Measure resistance between CAN_H and CAN_L with ignition off — typical ~60 Ω (two 120 Ω terminators in parallel)
• Check for short to 12V or ground from each CAN line using an ohmmeter (with harness disconnected at module)

Signal parameters

• CAN_H typical recessive ~2.5–3.5 V, dominant ~1.0–1.5 V (differential ±2 V approx)
• CAN_L typical recessive ~1.5–2.5 V, dominant ~0.5–1.5 V
• Differential voltage CAN_H - CAN_L ≈ 2 V during dominant bits, ≈ 0 V during recessive bits
• Termination resistance between CAN_H and CAN_L ≈ 60 Ω (two 120 Ω terminators in parallel)
• Bus error counters/Bus-Off flag (module-specific) — look for incrementing error frames or bus-off status
• Supply to CAN transceiver (Vbat) and ground continuity at module

Similar codes