Meaning of Code P1391
The Isuzu P1391 code on Isuzu vehicles indicates a problem in the camshaft position sensor (CMP) circuit. This sensor plays a crucial role in synchronizing the fuel injection system and ignition.
Severity of the Problem
- Moderate to High: This fault can cause:
- ⚠️ Starting problems
- 🚗 Poor engine performance
- ⛽ Increased fuel consumption
- 🌫️ Increased pollutant emissions
Common Symptoms
- 🚗 Engine idling irregularly
- ⚡ Loss of power during acceleration
- ⚠️ Check engine light on
- 🔥 Occasional misfires
- 🔋 Cold weather starting problems
Possible Causes
- Electrical problems:
- Faulty CMP sensor
- Damaged wiring or corroded connectors
- Short circuit or open circuit in the harness
- Mechanical problems:
- Damaged camshaft gear wheel
- Misaligned timing
- Other causes:
- Power supply or grounding issue
- Engine Control Module (ECM) failure
Diagnostic Procedure
Step 1: Visual Inspection
- 🔍 Locate the CMP sensor (usually near the camshaft pulley)
- 🔌 Check the condition of the connector and wiring
- � Look for signs of damage or corrosion
Step 2: Electrical Tests
- 🔋 Check the sensor’s power supply (5V) and ground
- 📏 Measure the sensor’s resistance (compare to specifications)
- ⚡ Test the output signal with an oscilloscope
Step 3: Mechanical Check
- ⚙️ Inspect the gear wheel for missing or damaged teeth
- 🔧 Check the timing alignment
Step 4: Advanced Diagnostics
- 💻 Use an OBD-II scanner to:
- Read live sensor data
- Check for associated codes
- Analyze the CMP signal graph
Common Repairs
- 🔧 Replace the faulty CMP sensor
- 🔌 Repair or replace damaged wiring
- ⚙️ Correct the timing alignment if necessary
- 💻 Update the ECM software if required
Prevention Tips
- 🛠️ Replace the CMP sensor as part of preventive maintenance
- 🔍 Regularly inspect wiring and connectors
- ⛽ Use quality OEM parts
Average Repair Cost
- CMP sensor: €50-€150
- Labor: €50-€150
- *Estimated total: €100-€300*
Conclusion
The P1391 code on Isuzu requires immediate attention to avoid potential engine damage. Accurate diagnosis will identify the exact cause and allow for appropriate repairs.
🔧 Professional tip: If you are not familiar with electrical diagnostics, consult a qualified mechanic specialized in Isuzu vehicles.
🚗 Is your Isuzu displaying this code? Share your experience in the comments to help other owners!