Code
U1308
PEUGEOT
U — Network/User
No communication with the engine management ECU fault: Missing engine control ECU / no signal
Views:
UK: 0
EN: 2
RU: 2
AI status
Completed
Completed
100%
Causes
- Blown fuse or lost power supply to engine ECU
- Poor or missing ground to the engine ECU
- Disconnected/corroded ECU connector or damaged pins
- Open/short in the CAN bus wiring between ECU and gateway/modules
- Failed engine management ECU (internal fault)
- Faulty gateway/vehicle communications module or software mismatch
Symptoms
- Instrument cluster shows engine ECU not detected or multiple network errors
- Engine may not start or runs in limp mode / reduced performance
- Misleading or missing engine data on dashboard (RPM, coolant temp)
- Multiple related modules log communication errors
- Vehicle may stall or fail to crank if ECU power is lost
What to check
- Connect a diagnostic scanner to read live data and confirm U1308 and any related U‑codes
- Check battery voltage (stable >12 V) and ignition supply during cranking
- Visually inspect engine ECU connector and wiring harness for corrosion, disconnection or damage
- Check fuses and relays supplying the engine ECU and gateway
- Measure ground continuity from ECU ground pins to chassis
- Measure CAN bus voltages at the engine ECU connector and at gateway/cluster connectors
Signal parameters
- CAN bus idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both near mid‑rail)
- CAN bus dominant: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2 V)
- Termination resistance (both ends): ≈ 60 Ω measured between CAN_H and CAN_L
- Expected ECU power: battery voltage at ECU supply pin with ignition on (~11–14 V)
- Ground resistance: low ohms to chassis (typically
Diagnostic algorithm
- Record fault with a capable scanner and note time/states and any related U‑codes
- Attempt communication with engine ECU via diagnostic tool; note if ECU responds or is completely silent
- Check battery voltage and stable power supply; recharge or connect a stable battery if required
- Visually inspect and reseat engine ECU connector; check for bent/broken pins and corrosion
- Check fuses/relays for ECU power and replace if blown; verify relay control circuits
- Measure supply and ground at the ECU connector with ignition ON and cranking
- Measure CAN_H and CAN_L voltages at the ECU connector and at a known good node (gateway/cluster); compare readings
- Measure resistance across CAN_H and CAN_L with ignition off — expect ~60 Ω if terminations present
- If wiring concerns identified, perform continuity and short tests (backprobe, wiggle tests) and repair damaged wiring or connectors
- If wiring and power/ground are OK and ECU still silent, swap with known‑good ECU or perform ECU bench diagnostics if available, or update/reflash gateway and ECU software per manufacturer procedures
- Clear codes and retest after each repair; road test to confirm issue is resolved
Likely causes
- ECU battery supply fuse blown or relay fault
- Loose or corroded multi‑pin connector at engine ECU
- Damaged CAN_H or CAN_L wiring (chafing, pinched, rodent damage)
- Missing CAN termination resistor or short to battery/ground on bus
- Gateway/module software error or lost configuration after battery disconnect
- Intermittent ground connection at engine bay grounding point
Fault status
Status
No communication with engine management ECU — engine control module missing or not responding on vehicle network.
Repair difficulty: Medium
Diagnostic time: 1.5–3 hours
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