Contents
1. Firing Order Specification
The correct firing order for the 2012 Honda Odyssey with the 3.5L V6 (J35Z2 engine) by an automotive engineering expert with 25+ years Honda powertrain experience | ASE Certified Master Technician is:
1 → 4 → 2 → 5 → 3 → 6
This sequence repeats continuously while the engine is running.
2. Cylinder Numbering
Honda uses a standard V6 cylinder numbering convention:
| Bank 1 (Rear – Transmission Side) | Bank 2 (Front – Radiator Side) |
|---|---|
| Cylinder 1 (Frontmost on Bank 1) | Cylinder 2 (Frontmost on Bank 2) |
| Cylinder 3 | Cylinder 4 |
| Cylinder 5 | Cylinder 6 |
Textual Diagram:
Firewall (Rear of Engine)
————————-
Bank 1 (Transmission Side) Bank 2 (Radiator Side)
————————- ————————
Cyl 1 (Front) Cyl 2 (Front)
Cyl 3 (Middle) Cyl 4 (Middle)
Cyl 5 (Rear) Cyl 6 (Rear)
————————-
Radiator (Front of Engine)
————————-
Bank 1 (Transmission Side) Bank 2 (Radiator Side)
————————- ————————
Cyl 1 (Front) Cyl 2 (Front)
Cyl 3 (Middle) Cyl 4 (Middle)
Cyl 5 (Rear) Cyl 6 (Rear)
————————-
Radiator (Front of Engine)
3. Importance of Correct Firing Order
A proper firing order is critical because:
- Engine Balance: Optimizes combustion forces to reduce vibration
- Exhaust Scavenging: Proper sequence helps maintain exhaust gas flow
- Fuel Efficiency: Ensures optimal timing of combustion events
- Emissions Control: Prevents unburned fuel from entering the exhaust
Risks of Incorrect Firing Order:
- Severe engine misfires (potentially damaging catalytic converters)
- Rough idle and hesitation during acceleration
- Increased fuel consumption and reduced power
- Potential backfiring through the intake or exhaust
- Triggering of check engine lights and emission codes
4. Diagnostic Symptoms
Signs your firing order may be incorrect:
- Check Engine Light with codes:
- P0300: Random/Multiple Cylinder Misfire
- P0301-P0306: Specific cylinder misfires
- Engine runs noticeably rough at idle
- Loss of power, especially under load
- Engine may shake or vibrate excessively
Verification Steps:
- Connect OBD-II scanner and check for misfire codes
- Use a timing light to verify spark sequence matches the specification
- Perform a relative compression test to rule out mechanical issues
- Inspect spark plug wires/coils (if applicable) for proper routing
5. Torque Specifications
| Component | Torque Specification | Notes |
|---|---|---|
| Spark Plugs | 13 ft-lbs (18 Nm) | Always use new washers |
| Ignition Coils | 7 ft-lbs (9.8 Nm) | Coil-over-plug design |
| Spark Plug Wire Boots | N/A (push-on connection) | Ensure a ‘click’ when properly seated |
Critical Precautions:
- Always hand-thread spark plugs before tightening to avoid cross-threading
- Apply dielectric grease to coil boots to prevent moisture intrusion
- Never remove more than one spark plug wire/coil at a time to maintain reference
- Let the engine cool before working with ignition components
6. Recommended Tools
- Spark plug socket (5/8″ or 16mm) with rubber insert
- Torque wrench (3/8″ drive, in-lb and ft-lb scales)
- OBD-II scanner with live data capability
- Inductive timing light (for verification)
- Dielectric grease (for coil boots)
- Safety glasses and mechanic’s gloves
7. Service Procedure
- Disconnect the battery’s negative terminal
- Remove engine cover (if equipped)
- Clean around coils before removal to prevent debris entry
- Working one cylinder at a time:
- Remove the ignition coil
- Inspect the boot for damage/cracking
- Remove and inspect the spark plug
- Gap new plug (if required) to 1.0-1.1mm (0.039-0.043 in)
- Install a new plug with proper torque
- Reinstall coil
- Reconnect the battery and test the operation
Professional Tip:
The J35Z2 engine features Honda’s Variable Cylinder Management (VCM) system. When diagnosing misfires unrelated to ignition components, always consider possible VCM solenoid or oil control issues, especially on cylinders 1, 2, and 3 (Bank 1) deactivated during ECO mode.
