Code
U1313
PEUGEOT
U — Network/User
Fault in communication with the ABS/ESP ECU on the CAN: No signal / partial triggering message fault
AI status
Completed
Completed
100%
Causes
- Open or short in CAN bus wiring between ABS/ESP ECU and rest of network
- Damaged or corroded connector(s) at the ABS/ESP ECU
- Lost or intermittent power or ground to the ABS/ESP ECU
- Faulty CAN transceiver or internal ECU fault in the ABS/ESP module
- Blown fuse or relay supplying the ABS/ESP ECU
- Module configuration/programming mismatch after replacement
Symptoms
- ABS warning lamp and/or ESP/traction control lamp illuminated
- Loss of ABS/ESP functionality (no ABS activation during braking)
- Other modules reporting related communication errors
- Intermittent or permanent fault stored in multiple control units
- Possible reduced braking system functionality or limp-home behaviour
What to check
- Read and record all stored and pending DTCs from ABS and other modules
- Check vehicle battery voltage and health
- Visual inspection of ABS ECU connector(s) for corrosion, bent pins, moisture
- Check related fuses and relays for continuity and correct supply
- Scan CAN bus for presence of ABS alive messages and other module traffic
- Measure CAN_H/CAN_L voltages at ABS ECU connector with key ON
Signal parameters
- Presence/absence of ABS/ESP ECU 'alive' messages and their message IDs
- Message frequency (Hz) of ABS messages on CAN bus
- CAN_H and CAN_L resting voltages with ignition ON
- Differential voltage when bus is active (CAN_H - CAN_L)
- CAN error counter increases or bus-off state indications
- Power supply (VBATT) and ground voltage at ABS ECU
Diagnostic algorithm
- Connect a capable scan tool to the vehicle. Read and save all fault codes from all modules. Note freeze-frame and occurrence conditions.
- Attempt to view live CAN traffic and look for ABS/ESP message IDs. Confirm whether ABS module is transmitting an 'alive' message.
- Perform a visual inspection of ABS ECU connector and associated wiring for corrosion, bent pins, water ingress, or physical damage. Repair as needed.
- Check fuses and relays supplying the ABS ECU. Verify supply voltage and ground at the ABS ECU connector with the ignition ON and engine OFF.
- Measure CAN_H and CAN_L voltages at the ABS ECU connector and at another module connector to compare. Look for open, short-to-ground, or short-to-battery conditions.
- If intermittent, perform wiggle test on harness connectors while monitoring CAN traffic and DTCs to reproduce fault.
- Isolate segments: disconnect the ABS ECU (with ignition OFF) and check bus behavior and termination to identify whether the ECU causes bus errors when connected.
- Check termination resistors (usually 60 ohm across CAN_H and CAN_L when two 120 ohm terminators present) and continuity between bus branches.
- If wiring and power/ground are good but no messages, consider ABS ECU CAN transceiver/internal failure. Verify software version and coding if ECU was recently replaced.
- After repairs or module replacement, clear codes and road-test to confirm message presence and that no U1313 or related communication codes return.
Likely causes
- Broken/damaged CAN_H or CAN_L wires near ABS ECU or junctions
- Loose or corroded ABS ECU connector pins
- ABS/ESP ECU not powered (fuse, relay, supply wiring)
- Failed CAN transceiver inside ABS/ESP unit
- Missing or failed bus termination resistor
Fault status
Status
Communication fault with ABS/ESP ECU on CAN bus: no signal or partial message received.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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