Vehicle: MG ZS (EU)
Mileage: Approx. 45,800 km
Inspection Type: Vehicle Diagnostic Assessment
Customer Background: The customer contacted Fault Fixer after multiple garages and roadside services were unable to access the vehicle’s diagnostic systems or communicate correctly with the control modules. Warning lights were present and fault codes could not be reliably retrieved elsewhere.
Fault Fixer was able to access the vehicle software fully and carry out a complete system-level diagnosis.
The Problem: Multiple Fault Codes, No Clear Answers
At the time of arrival, the vehicle was reporting multiple communication-related fault codes across several control units.
Key fault codes included:
- U0100 – Lost Communication with Engine Control Module (ECM)
- U0401 – Invalid Data Received from Engine Control Module (ECM)
These faults were logged across multiple systems, including:
- ABS (Anti-lock Braking System)
- EPS (Electric Power Steering)
- BCM (Body Control Module)
- SDM (Airbag / Safety Module)
- ECM (Engine Control Module)
When faults appear across unrelated systems simultaneously, it strongly suggests a vehicle-wide electrical or power supply issue, rather than multiple component failures.
Why Other Diagnostics Often Fail on Vehicles Like This
On modern vehicles, particularly newer platforms like MG, unstable system voltage can:
- Prevent diagnostic tools from communicating reliably
- Cause control modules to drop offline intermittently
- Block access to certain software functions
This is why other providers struggled to diagnose the vehicle correctly.
Fault Fixer’s diagnostic equipment and methodology allowed stable access to all systems, even with underlying voltage instability.
Battery & Electrical Assessment: The Real Cause Emerges
Ignition-Off Battery Voltage Findings:
- Voltage fluctuating around 12.3V
- Intermittent drops below 11V with no electrical load applied
These readings are not sufficient for stable control unit operation.
Low or unstable voltage at this level is known to cause:
- Control module resets
- CAN bus communication interruptions
- False or misleading fault code logging
- Warning lights across multiple systems
This pattern is typical of an internally failing battery, often due to weak or intermittently failing cells.
Why the Fault Codes Look So Serious (But Weren’t)
In addition to communication faults, the system logged several “engine aging” fault codes.
These are commonly recorded when:
- Control modules experience unstable voltage
- Sensor signals become temporarily unreliable
- The engine management system enters fallback strategies
Crucially:
- No wiring damage was found
- No control unit failures were detected
- No genuine sensor or mechanical faults were present
System Verification: Proving What Was Not Faulty
Live data analysis confirmed:
- ABS wheel speed sensors functioning correctly
- Steering angle sensor operating smoothly and within tolerance
- No ABS or stability control faults present
- Engine live data stable throughout testing
- No active engine fault codes
GPF (Gasoline Particulate Filter) data showed:
- Low soot load
- Low differential pressure
- No indication of exhaust system faults
This ruled out braking, steering, engine, and exhaust system failures entirely.
After Fault Code Clearing: The Proof
All fault codes were cleared during the inspection.
Results:
- No fault codes returned
- CAN communication remained stable
- All control units operated normally
- Vehicle functioned correctly throughout testing
This confirmed the original faults were voltage-related, not component-related.
Final Diagnosis
The root cause of the issue was an end-of-life vehicle battery causing unstable system voltage.
This instability:
- Disrupted module communication
- Triggered multiple warning lights
- Logged misleading fault codes
- Prevented some diagnostic tools from accessing vehicle software
Once identified and addressed diagnostically, the vehicle systems returned to normal operation.
Recommendations
- Battery replacement strongly recommended
- This will prevent:
- Recurring communication faults
- Warning lights
- System resets
- Diagnostic access issues in future
- Recurring communication faults
Why This Case Study Matters
This job highlights several critical points for modern vehicle owners:
- Multiple warning lights do not always mean multiple faults
- Software access issues often stem from electrical instability, not failed modules
- Replacing parts without diagnosis leads to wasted time and cost
- Proper diagnostics require both access and interpretation
Most importantly, it shows why Fault Fixer is called in when others can’t get access.
The Fault Fixer Difference
This vehicle wasn’t fixed by guessing, replacing parts, or clearing codes blindly.
It was fixed by:
- Accessing systems others couldn’t
- Understanding network-wide fault patterns
- Identifying the true root cause
- Explaining it clearly to the customer
That’s diagnostics, not just scanning.