Vehicle: Peugeot Expert (2018)
Registration: NV18
Inspection Type: Engine Management System Diagnosis
Primary Issue: Complete non-start condition
Customer Complaint: Ignition On, But No Crank and No Start
The vehicle presented with:
- Ignition active
- Engine does not crank
- Immobiliser lock active
- No communication with Engine Management ECU
- Vehicle completely inoperative
This is a classic scenario where many garages initially suspect:
- Flat battery
- Starter motor failure
- Immobiliser key issue
- Fuse or wiring fault
However, structured diagnostics told a very different story.
Diagnostic Summary: ECU Communication Failure Confirmed
A full system scan revealed critical network communication faults:
Engine ECU Communication:
- No Communication (U1F2E, U1108, U1308)
Immobiliser:
- Start Blocked (B1808)
ABS / ESP:
- Software Mismatch / Communication Error (U1508)
Multiple control modules were reporting loss of communication with the Engine Control Unit (ECU).
When several independent systems cannot communicate with the ECU, it indicates a network-level failure, not a simple component issue.
Why This Caused a Complete Non-Start
Modern vehicles rely on the ECU to:
- Authorise immobiliser release
- Control starter engagement
- Coordinate network communication
- Enable powertrain operation
In this case:
- The immobiliser was not receiving “start authorisation”
- ABS and steering modules were reporting incompatible data
- The central BSI could not establish communication
Without ECU communication, the vehicle cannot start, even if the battery and starter are healthy.
Critical Checks Performed (To Rule Out External Causes)
Before concluding ECU failure, the following inspections were completed:
Battery
- Brand new battery installed
- Voltage level confirmed OK
Fuse Checks
- Engine management fuses manually checked
- All fuses confirmed OK
Power Supply & Ground
- ECU power supply tested
- Correct voltage confirmed
- Ground connections verified
Wiring Inspection
- Visual inspection of engine bay wiring
- No damage or loose connections found
All external supply conditions were correct.
This ruled out:
- Flat battery
- Power supply issue
- Blown fuses
- Obvious wiring faults
The ECU had correct power and ground, yet remained completely unresponsive.
Network Communication Analysis: The Key Evidence
Multiple systems reported:
- No communication with Engine Management Computer
- Incompatible or corrupted data
- Start authorisation blocked
When:
- Power supply is correct
- Grounds are correct
- Wiring is intact
- Battery is new
and communication is still impossible
The fault lies internally within the ECU itself.
Final Diagnosis: Internal ECU Failure
Despite correct voltage and ground supply, the Engine Control Unit remained:
- Completely unresponsive
- Unable to communicate with any network modules
- Unable to authorise immobiliser release
- Unable to control vehicle systems
This confirms an internal ECU failure.
Recommended Repair Strategy
To restore full vehicle operation, the following was recommended:
- ECU Replacement
- Install new Engine Management Computer
- Coding & Programming
- Program ECU to vehicle specification
- Immobiliser Pairing
- Pair new ECU with immobiliser system
- Full System Validation
- Complete diagnostic scan
- Confirm full network communication restored
Replacing the ECU is critical to restoring vehicle functionality.