1. Meaning of Code Buick P1393
P1393 on Buick indicates:
“Intermittent problem with the camshaft position sensor (CMP) circuit – Bank 1”
Consequences:
- Engine light illuminated
- Performance degradation
- Risk of difficult starting
2. Affected Buick Models
| Model | Engine | Years | Typical Mileage |
|---|---|---|---|
| Enclave | 3.6L V6 | 2012-2017 | 130,000-190,000 km |
| Regal | 2.0L Turbo | 2011-2017 | 100,000-160,000 km |
| LaCrosse | 3.8L V6 | 2005-2009 | 160,000-240,000 km |
| Encore | 1.4L Turbo | 2013-2022 | 80,000-140,000 km |
3. Probable Causes
Electrical Problems (70%):
- Faulty CMP sensor (ref. GM 12677925)
- Damaged wiring (especially near the exhaust)
- Oxidized connector (X3 at ECM)
- Unstable supply voltage
Mechanical Problems (25%):
- Excessive camshaft play
- Stretched timing chain (3.6L)
- Dirt on the tone wheel
Others (5%):
- Outdated ECM software
- Grounding issue
4. Diagnostic Procedure
Step 1 – Visual Checks:
- Check oil level
- Inspect CMP sensor connector
- Check wiring condition
Step 2 – Electrical Tests:
| Test | Method | Normal Values |
|---|---|---|
| Supply voltage | Ignition ON | 5V ±0.5V |
| CMP resistance | Sensor disconnected | 500-1500Ω |
| Signal | Oscilloscope | Clean square signal |
Step 3 – Mechanical Checks:
- Check chain tension (3.6L)
- Inspect tone wheel
- Check oil pressure (>1.4 bar)
5. Repair Solutions
For 3.6L V6:
- Replace CMP sensor
- Check chain tensioner
- Clean ECM connector X3
For 2.0L Turbo:
- Inspect wiring near turbo
- Replace both sensors (intake/exhaust)
- Check PCV system
6. Technical Data
- Tightening torque: 10 Nm
- Sensor gap: 0.5-1.5mm
- Inspection interval: 100,000 km
7. Estimated Costs
| Service | Cost (EUR) | Warranty |
|---|---|---|
| Sensor replacement | 150-300€ | 2 years |
| Wiring repair | 200-450€ | 1 year |
| Diagnostic | 80-150€ | – |
8. Important Tips
- Use only ACDelco sensors
- Always check the entire wiring
- Reset adaptations after repair
9. FAQ
Q: Can I drive with this code?
→ Limited to 50 km maximum
Q: Why prefer OEM parts?
→ Failure rate <5% vs >40% for generic parts
Q: Recommended prevention?
- Regular oil changes
- Annual wiring inspection
- Connector cleaning
10. Conclusion
To permanently resolve P1393:
- Complete diagnostic with GM scanner
- Thorough electrical verification
- Use of original parts
⚠ Important: Consult a certified GM technician for recurring problems. 3.6L engines require special attention to chain tension.