DF101

Code

RENAULT D

-> PC121 - multiplexed trajectory control Link

Brand: RENAULT

Type: D

Views: UK: 4 EN: 9 RU: 5

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Page language: EN

Causes

Open, short or high resistance in CAN/multiplex wiring between trajectory control module and network
Corroded, loose or damaged connector(s) at modules or junctions
Bus termination resistor missing or shorted
Low battery or poor ground at one or more modules
One or more control modules (trajectory control, ABS, gateway) not responding or faulty
Software/configuration mismatch after module replacement or update

Symptoms

Warning lamp(s) for stability/trajectory control or ABS illuminated
Loss or reduction of electronic trajectory/stability control functions
Diagnostic tool reports communication errors with trajectory or related control modules
Possible limp/limited drive modes or messages on instrument cluster
Intermittent faults that may clear and reappear with ignition cycles or road vibration

What to check

Read full DTC list and freeze frame data with a suitable Renault-capable scan tool; note related U-codes and module addresses
Perform visual inspection of wiring, connectors and grounding points for trajectory control, ABS and gateway modules
Check battery voltage and main power/ground at related modules (with ignition on and engine cranking)
Inspect fuses and fusible links feeding the modules
Measure resistance between CAN H and CAN L across the bus (expected ~60 ohms total) and check for open/short to battery/ground
Check connector pins for corrosion, bent pins or moisture

Signal parameters

Typical CAN recessive voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (bus idle)
Typical CAN dominant voltages: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
Bus termination: ~60 ohms across CAN_H and CAN_L (two 120 Ω terminators in parallel)
Bitrate: depends on vehicle (commonly 500 kb/s or 250 kb/s); confirm model-specific bitrate with OEM documentation
No DC short to battery (+12 V) or ground on CAN_H/CAN_L lines

Diagnostic algorithm

Retrieve and record all DTCs and freeze frame data. Note which modules report communication loss.
Clear codes and attempt to reproduce the fault (key cycles, engine start, road test) while monitoring live data.
Visually inspect wiring, connectors and module mounting positions for damage or corrosion; repair any obvious issues.
Verify stable battery voltage and proper grounds at the trajectory control module and gateway module.
Measure continuity and resistance of CAN_H and CAN_L between modules and to the gateway; check for shorts to battery/ground.
Measure total bus resistance across CAN_H/CAN_L (expect ~60 Ω). An open or very high resistance indicates missing termination or open wire; very low resistance indicates short.
Use an oscilloscope or CAN sniffer to observe waveforms and message traffic. Look for missing modules, repeated error frames, or corrupted messages.
Isolate sections of the bus if the fault is intermittent: disconnect suspect module connectors one at a time to see if bus behavior or codes change.
If a module is non-responsive but wiring and power/grounds are confirmed good, reprogram or swap with a known-good module per OEM procedures (retain immobiliser/security steps).
After repairs, clear codes and perform functional test and road test to confirm normal operation.

Likely causes

Faulty connector or wiring harness (chafing, water ingress) on the CAN/multiplex lines
Missing or incorrect termination (open/shorted resistor) on the bus
Failed module (trajectory control or gateway) not responding to bus messages
Intermittent power/ground to a module causing sporadic loss of communication

Fault status

⚠️ Status

Multiplexed trajectory control link fault (PC121): communication error on vehicle bus. Check CAN/multiplex wiring, connectors, termination, power/ground, and module response.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-4 hours

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DF101 — -> PC121 - multiplexed trajectory control Link