1. Specific Meaning of Isuzu P1392
The P1392 code on Isuzu vehicles indicates:
“Intermittent misalignment between CKP (crankshaft) and CMP (camshaft) signals”
Technical specificities:
- Primarily affects common rail diesel systems (4JJ1, 4HK1)
- Can disrupt injection timing
- Risk of engine power limitation
2. Affected Isuzu Models
| Model | Engine | Years | Critical Mileage |
|---|---|---|---|
| D-Max | 4JJ1-TC | 2011-2023 | 120,000-200,000 km |
| MU-X | 4JK1-TC | 2013-2023 | 100,000-180,000 km |
| NPR | 4HK1-TC | 2008-2023 | 150,000-250,000 km |
3. Main Causes (Isuzu Technical Data)
A. Mechanical Problems (60%)
- Timing belt wear (4JJ1/4JK1)
- Automatic tensioner failure
- Excessive timing gear play
B. Electrical Failures (30%)
- Faulty CMP sensor (Isuzu ref. 8-94185-392-0)
- ECM connector problem (moisture/corrosion)
- Damaged wiring near engine block
C. Other Causes (10%)
- Timing issue after maintenance
- Partial ECU failure
- Insufficient oil pressure
4. Official Isuzu Diagnostic Procedure
Step 1 – Initial Checks
- Check timing belt tension
- Visually inspect CKP/CMP sensors
- Verify engine oil level and quality
Step 2 – Electrical Tests
- CMP resistance: 800-1200Ω (at 20°C)
- CKP signal: 0.5-4V AC (during startup)
- Cable insulation test (>1MΩ)
Step 3 – Mechanical Checks
- Verify timing mark alignment
- Check tensioner pulley condition
- Measure gear play
5. Engine-Specific Solutions
For 4JJ1-TC (D-Max)
- Complete belt kit (Isuzu ref. 8-97228-858-0)
- Upgraded CMP sensor (2020+ version)
- ECM connector cleaning
For 4HK1-TC (NPR)
- Complete timing system inspection
- Seal replacement
- Oil pump verification
6. Key Technical Data
- Belt tension: 50-60 N (new)
- Minimum oil pressure: 3 bar (hot idle)
- Belt interval: 90,000 km or 5 years
7. Repair Costs
| Service | Cost (EUR) | Warranty |
|---|---|---|
| Sensor replacement | 180-350€ | 2 years |
| Complete timing kit | 600-1,200€ | 1 year |
| Electronic diagnostic | 80-150€ | – |
8. Mistakes to Avoid
- Using non-genuine belt kits
- Neglecting tensioner pulley replacement
- Forgetting to purge system after service
9. Technical FAQ
Q: Is this code critical on Isuzu diesel?
→ Yes, can cause severe injection problems
Q: Can I drive while waiting for repair?
→ Not recommended – Risk of injection pump damage
Q: Recommended inspection frequency?
- Check every 30,000 km after 100,000 km
- Preventive belt replacement at 90,000 km
10. Conclusion
To resolve P1392 on Isuzu:
- Complete timing system verification
- Thorough electrical control
- Use of genuine Isuzu parts
⚠️ Important: Isuzu diesel engines are sensitive to injection timing. Consult a certified Isuzu technician for this type of fault.