The P1390 code on Buick vehicles indicates a critical misalignment between the crankshaft and the camshaft. This error prevents the ECU from properly synchronizing injection and ignition, risking engine damage. Here is the complete guide.
❌ Common Symptoms
- Engine that does not start (caused by a loss of synchronization).
- Jerking and stalling during acceleration.
- Check engine light on + sudden loss of power.
- Abnormal noise (knocking or grinding near the timing system).
🔧 Main Causes
- Worn or misaligned timing belt/chain (major cause on Buick Century/Regal).
- Faulty crankshaft position sensor (CKP) or camshaft position sensor (CMP).
- Damaged reluctor wheel (missing or rusty teeth).
- Wiring problem: Short circuit, connector corrosion.
- Engine control module (ECU) fault (rare).
🔍 Diagnostic Procedure
- Check the timing belt/chain:
- Inspect the tensioner and alignment marks (common models: Buick Century 1997-2005, Regal).
- Look for broken teeth or excessive play.
- Test the CKP/CMP sensors:
- Measure resistance (CKP: 850–1350 Ω, CMP: 200–1000 Ω, depending on model).
- Inspect cables and connectors (oil deposits, oxidation).
- Examine the reluctor wheel:
- Check for missing teeth or magnetic debris (clean with a dry cloth).
- Scan live data:
- Compare CKP/CMP signals using an OBD2 tool (e.g., Tech2). A misalignment > 5° confirms P1390.
🛠️ Recommended Repairs
| Problem | Solution | Recommended Parts (Buick Ref.) |
|---|---|---|
| Worn timing belt | Replace belt + tensioner pulleys | Gates kit TCKWP328 (for 3.1L V6) |
| Faulty CKP sensor | Install new sensor (check air gap: 0.5–1.5 mm) | ACDelco 213-1151 |
| Damaged reluctor wheel | Replace magnetic plate | Delphi FG1114 |
| Faulty wiring | Repair wires or replace harness | Standard Connector PT778 |
⚠️ Warning: A desynchronized timing system can cause piston-valve collision. Stop the engine if abnormal noises occur!
📊 Technical Sheet
| Code | P1390 |
|---|---|
| Definition | CKP/CMP synchronization error |
| Sensitive Buick Models | Century, Regal, LaCrosse (1996–2010) |
| Urgency | High (risk of engine failure) |
💡 Key Tips
- Use a specialized timing tool (e.g., Kent-Moore J-42450 for Buick) after replacing the timing system.
- Check battery voltage during the procedure (low voltage distorts signals).
- Prefer ACDelco/Delphi parts for optimal compatibility.
- Reset the ECU after repair (clear code + relearn parameters).
Conclusion
The P1390 code on Buick indicates a critical mechanical or electrical problem between the crankshaft and camshaft. Prompt action is essential to avoid costly engine damage. Start by inspecting the timing system and sensors (CKP/CMP), then check the electrical circuit. If the fault persists, consult a specialist equipped with a GM Tech2 scanner for an in-depth analysis.