Starting problems are a common issue affecting VY and VZ Commodores. These vehicles use a combination of mechanical, electrical, fuel, and security systems to start the engine, meaning that even a small fault in one area can prevent the vehicle from starting.
Because of this complexity, starting issues can be difficult to diagnose and are often misattributed to major component failure when the cause is actually something simple like a weak battery, faulty relay, or sensor issue.
How the Starting System Works
To start the engine, several systems must work together:
Key Components
- Battery
- Starter motor
- Ignition switch
- BCM (Body Control Module)
- Crank angle sensor
- Fuel pump system
- Immobiliser system
- Engine ECU
If any one of these systems fails, the engine may not start.
Common Starting Symptoms
Warning Signs
- No crank condition
- Slow cranking
- Engine cranks but won’t start
- Intermittent starting
- Clicking noise when turning key
- Security light flashing
- Stalling shortly after starting
Different symptoms help identify different causes.
1. Flat or Weak Battery
The most common cause of starting problems.
Symptoms
- Slow cranking
- No crank
- Dimming lights
- Clicking noise
Causes
- Ageing battery
- Short trips
- Charging system issues
2. Starter Motor Failure
A worn starter motor is common in high-kilometre Commodores.
Symptoms
- Single click when turning key
- No crank condition
- Intermittent starting
Causes
- Worn brushes
- Solenoid failure
- Internal electrical wear
3. Ignition Switch Problems
The ignition switch sends power to key systems.
Symptoms
- No crank
- Accessories not working
- Intermittent starting issues
Causes
- Electrical contact wear
- Internal switch failure
4. Crank Angle Sensor Failure
A critical engine management sensor.
Symptoms
- Engine cranks but won’t start
- Sudden engine cut-out
- No spark or fuel pulse
Causes
- Heat damage
- Sensor failure
5. Fuel Pump Issues
Fuel delivery problems often prevent starting.
Symptoms
- Engine cranks but does not start
- No fuel pump noise
- Stalling issues
Causes
- Fuel pump wear
- Relay failure
- Wiring faults
6. BCM and Immobiliser Faults
The BCM controls vehicle security and immobilisation.
Symptoms
- Security light flashing
- No-start condition
- Key not recognised
Causes
- BCM failure
- Key transponder issues
- Communication faults
7. Poor Earth Connections
Ground faults are often overlooked.
Symptoms
- Intermittent starting
- Electrical glitches
- Weak cranking
Causes
- Corroded earth points
- Loose wiring connections
8. Starter Relay or Fuse Issues
Simple but common faults.
Symptoms
- No crank
- Intermittent starting
- Clicking noise
Causes
- Relay failure
- Blown fuse
Diagnosing Starting Problems
Step 1: Check Battery
Test:
- Voltage (should be around 12.6V at rest)
- Load condition
Step 2: Listen for Cranking
No Crank
Usually electrical or starter related.
Cranks But No Start
Usually fuel, spark, or sensor related.
Step 3: Check Fuel Pump Operation
Turn ignition to ON and listen for pump prime.
Step 4: Check Security Light
Flashing security light may indicate immobiliser issues.
Step 5: Scan for Fault Codes
Use an OBD scanner to check for:
- Sensor faults
- Immobiliser codes
- ECU errors
Common Misdiagnoses
Fuel Pump vs Crank Angle Sensor
Both can cause no-start conditions.
Battery vs Starter Motor
A weak battery can mimic starter failure.
BCM vs Ignition Switch
Both can prevent starting.
Sensor Fault vs Fuel Issue
Crank sensor failure often appears as fuel system failure.
Cold Start Problems
Some VY and VZ Commodores experience starting issues when cold.
Causes
- Weak battery
- Fuel pressure loss
- Sensor sensitivity
Intermittent Starting Issues
One of the hardest faults to diagnose.
Common Causes
- Loose wiring
- Faulty relays
- Crank sensor intermittency
- BCM issues
Preventing Starting Problems
Maintain Battery Health
Replace ageing batteries early.
Service Fuel System
Keep fuel pump and filter in good condition.
Inspect Earth Connections
Clean and tighten grounds regularly.
Replace Worn Sensors Early
Crank sensors are a common failure point.
Warning Signs Requiring Immediate Attention
- Complete no-start condition
- Repeated stalling
- Security system faults
- Rapid battery drain
- Clicking with no crank
These should be diagnosed promptly.
Starting problems in VY and VZ Commodores can be caused by a wide range of issues, from simple battery faults to more complex sensor or immobiliser failures. Because multiple systems are involved, proper diagnosis is essential to avoid unnecessary parts replacement.
In most cases, faults can be traced to a small number of common causes such as batteries, starter motors, crank angle sensors, fuel delivery issues, or BCM-related problems. With systematic testing, most starting issues can be identified and repaired efficiently.
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