P1338

What it means

P1338 on a Volkswagen means the engine control unit has detected an open circuit or a short to battery positive in the camshaft position (CMP) sensor circuit for bank 1. The control unit monitors the sensor's signal and supply and set the code because the voltage or signal was outside the expected range. The exact sensor location and wiring layout depend on the model and engine.

Symptoms

• Engine management light on
• Long cranking or hard starting
• Engine runs rough or misfires
• Loss of power or reduced performance
• Car running in a limp-home mode
• Intermittent stalling

Possible causes

• Damaged, chafed or corroded wiring to the bank 1 camshaft position sensor, including an open circuit or a short to battery positivelikely
• Poor connection at the sensor plug, such as loose, corroded or pushed-back terminalslikely
• Faulty camshaft position sensorlikely
• Wiring fault or poor connection at the engine control unit connectorpossible
• Fault in the sensor's power supply or earth feed, for example a relay or fuse issue (depends on model)possible
• Internal fault in the engine control unitrare

How to diagnose

1. Read all stored fault codes and freeze frame data, and note whether the fault is current or intermittent and whether other camshaft or crankshaft sensor codes are present.
2. Visually inspect the bank 1 camshaft sensor, its plug and the wiring for chafing, heat damage, oil contamination and corrosion.
3. Disconnect and check the sensor connector terminals for tightness, bent pins and moisture, then reconnect and see whether the code returns after clearing.
4. Wiggle test the harness with the engine running or with live data displayed to see whether the signal drops out or the fault sets.
5. Using the wiring diagram for the specific model and engine, check the sensor supply voltage, earth and signal wire for continuity and for any short to battery positive.
6. Check the relevant fuses and supply relays for the sensor circuit as shown in the model's wiring information.
7. Inspect the engine control unit connector for damage or corrosion and test the signal wire continuity back to the control unit.
8. If the wiring tests good, compare the sensor signal against the crankshaft signal using live data or a scope, and replace the sensor if the signal is missing or incorrect.

How to fix

• Repair or replace damaged wiring and insulate or reroute the harness so it can't chafe again.
• Clean, repair or replace corroded or loose connector terminals and the plug.
• Replace the bank 1 camshaft position sensor if it fails testing, and fit a new seal where applicable.
• Restore the sensor supply or earth by repairing the fuse, relay or associated wiring fault.
• Repair or replace the engine control unit connector or, as a last resort once all else is proven good, the control unit itself.

Can I keep driving?

Nearby codes

• P1337VolkswagenCMP Sensor Bank 1 Short To Ground
• P1339VolkswagenCrankshaft Position Engine Speed Sensor Cross Connected