The Suzuki P1391 code on a Suzuki vehicle is typically related to a problem with the synchronization between the crankshaft and the camshaft or a malfunction of the camshaft position sensor (CMP). This fault can affect engine performance and illuminate the check engine light (CEL).
1. Meaning of Code P1391
The P1391 code means:
- “Correlation Error Between the Crankshaft Position Sensor (CKP) and the Camshaft Position Sensor (CMP)”
- The engine control unit (ECU) detects an abnormal discrepancy between the signals from the two sensors.
Affected Suzuki Models (among others):
- Suzuki Swift
- Suzuki Grand Vitara
- Suzuki SX4
- Suzuki Baleno
2. Possible Causes of P1391
A. Mechanical Problems
- Misaligned timing belt (off by one or more notches)
- Stretched or worn timing chain (if the engine is equipped with one)
- Problem with the tensioner or timing pulleys
B. Electrical/Sensor Problems
- Faulty camshaft position sensor (CMP)
- Defective crankshaft position sensor (CKP)
- Damaged/corroded wires or connectors
C. Other Possible Causes
- Engine oil problem (insufficient pressure affecting the timing actuator)
- Problem with the variable valve timing (VVT) actuator (if the engine is equipped with one)
- ECU failure (rare)
3. Diagnosis and Solutions
Step 1: Check the Timing Belt/Chain
- Check the alignment of the marks (crankshaft and camshaft).
- If the belt/chain is worn or misaligned, replace it and correctly realign the timing.
Step 2: Test the CKP and CMP Sensors
- Disconnect and measure the resistance with a multimeter (check the manual specifications).
- Clean the sensors (sometimes dirt can interfere with the signal).
- Replace the faulty sensor if necessary.
Step 3: Inspect the Wiring and Connectors
- Check for cut, chafed, or corroded wires.
- Clean the connectors with electrical contact cleaner spray.
Step 4: Check the Engine Oil and VVT Actuator
- Check the oil level and quality (oil that is too old can clog the VVT system).
- If the engine has a VVT system, check its operation.
Step 5: Reset the Fault and Test
- Clear the code with an OBD2 tool and see if it returns after a road test.
- If the code reappears, check the ECU (rare but possible failure).
4. Conclusion
The P1391 code on Suzuki typically indicates a engine timing problem (timing system or sensors).
- Priority 1: Check the timing belt/chain.
- Priority 2: Test the CKP/CMP sensors and their wiring.
If the problem persists after these checks, a more in-depth analysis with an advanced scanner may be necessary.