The Volkswagen P1391 code on a Volkswagen (Golf, Passat, Polo, Tiguan, etc.) generally indicates a problem with the correlation between the crankshaft position sensor (CKP) and the camshaft position sensor (CMP). This fault can lead to rough idling, loss of power, or even the engine entering a limp mode.
1. Meaning of the P1391 code on Volkswagen
The P1391 code means:
- “Disagreement between the crankshaft position sensor (CKP) and camshaft position sensor (CMP) signals”
- The ECU detects that the two sensors are not synchronized as expected.
Affected Volkswagen models (among others):
- VW Golf (4, 5, 6, 7)
- VW Passat (B5, B6, B7)
- VW Polo (9N, 6R, 6C)
- VW Tiguan (1G, 2G)
- VW Jetta, Touran, Scirocco
2. Possible causes of P1391 on Volkswagen
A. Mechanical problems
- Incorrectly timed timing belt (off by one or more teeth)
- Stretched timing chain or faulty tensioner (on chain-driven engines, like the 1.4 TSI or 2.0 TDI)
- Problem with the tensioner pulley or worn chain guide
B. Sensor failure
- Faulty camshaft position sensor (CMP)
- Defective crankshaft position sensor (CKP)
- Dirty or damaged sensor (oil, debris)
C. Electrical problems
- Cut wires, oxidized connectors, or short circuits
- Poor sensor supply voltage
D. Other possible causes
- Problem with the variable valve timing (VVT) actuator if present
- Insufficient or poor-quality engine oil (affects VVT)
- ECU failure (rare but possible)
3. Diagnosis and solutions
Step 1: Check the timing belt/chain
- Check the alignment of the timing marks (crankshaft and camshaft).
- If the belt/chain is misaligned, worn, or loose, replace and recalibrate it.
- On chain-driven engines (e.g., 1.4 TSI, 2.0 TDI), check the condition of the chain and tensioner.
Step 2: Test the CKP and CMP sensors
- Use a multimeter to check the resistance (reference: technical manual).
- Clean the sensors (often soiled by oil).
- Replace the faulty sensor if necessary.
Step 3: Inspect the wiring and connectors
- Check for broken or oxidized wires between the sensors and the ECU.
- Clean the connectors with contact spray.
Step 4: Check the variable valve timing (VVT) and engine oil
- Check the oil level and quality (oil that is too old can block the VVT).
- If the engine has a VVT system, check its proper operation.
Step 5: Reset the fault and test
- Clear the code with VCDS (VAG-COM) or an OBD2 tool.
- Perform a road test to see if the code returns.
- If the problem persists, check the ECU (in-depth diagnosis required).
4. Conclusion
The P1391 code on Volkswagen is often related to:
✅ A timing issue (timing belt/chain) → Check the belt/chain.
✅ A faulty CMP or CKP sensor → Test and replace if necessary.
✅ An electrical problem (wires, connectors) → Inspect the wiring.