Damaged or frayed wiring in the camshaft sensor circuit, particularly at the connector or where the harness bends near the cylinder head.; Corroded or loose electrical connector at the camshaft position sensor.; Failed camshaft position sensor (internal open or short).; Short to battery voltage in the signal wire due to chafed insulation contacting a power wire.; Faulty engine control module (ECM) or poor connection at the ECM connector (less common).; Aftermarket or improperly installed electrical accessories tapping into the sensor circuit.

DTC codes / Volkswagen codes / P1338

P1338 · VolkswagenCMP Sensor Bank 1 Open Circuit Or Short To B+

Q: What does code P1338 mean?

CMP Sensor Bank 1 Open Circuit Or Short To B+. P1338 on Volkswagen vehicles indicates that the engine control module (ECM) has detected an open circuit or a short to battery voltage (B+) in the camshaft position (CMP) sensor circuit for bank 1. This means the signal wire from the sensor is either broken, disconnected, or inadvertently touching a power source, preventing the ECM from receiving a valid camshaft signal.

P1338 on Volkswagen vehicles indicates that the engine control module (ECM) has detected an open circuit or a short to battery voltage (B+) in the camshaft position (CMP) sensor circuit for bank 1. This means the signal wire from the sensor is either broken, disconnected, or inadvertently touching a power source, preventing the ECM from receiving a valid camshaft signal.

SystemPowertrain

Code typeVolkswagen specific

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms.
Engine may crank but fail to start or start after prolonged cranking.
Rough idle or misfire due to incorrect fuel and spark timing.
Reduced engine performance and poor fuel economy.
In some cases, the engine may stall intermittently or lack power during acceleration.

Common causes, most likely first

Damaged or frayed wiring in the camshaft sensor circuit, particularly at the connector or where the harness bends near the cylinder head.
Corroded or loose electrical connector at the camshaft position sensor.
Failed camshaft position sensor (internal open or short).
Short to battery voltage in the signal wire due to chafed insulation contacting a power wire.
Faulty engine control module (ECM) or poor connection at the ECM connector (less common).
Aftermarket or improperly installed electrical accessories tapping into the sensor circuit.

How to diagnose and fix it

Perform a visual inspection of the camshaft sensor and its wiring harness for obvious damage, corrosion, or loose connections.
Use a digital multimeter to check for battery voltage at the sensor connector with the key on, engine off; verify the presence of reference voltage and ground.
Disconnect the sensor and measure resistance across the sensor terminals; compare to manufacturer specifications to rule out a failed sensor.
Check the signal wire for continuity to ground and for short to battery voltage; repair any damaged wiring or replace the harness section as needed.
Clear the diagnostic trouble codes (DTCs) and road test the vehicle to verify the repair; if the code returns, proceed to more advanced diagnostics.
If wiring and sensor are good, inspect the ECM connector for corrosion or loose pins, and test the circuit from the ECM side.
As a last resort, substitute a known-good ECM to rule out internal driver failure, but only after confirming all other possibilities.

Common misdiagnosis traps for P1338

A short to B+ in the camshaft sensor circuit can be caused by a pinched wire behind the engine block, often overlooked during visual inspection.
The code can set intermittently due to vibration or heat, so a wiggle test of the harness while monitoring live data is crucial.
Replacing the camshaft sensor without checking the wiring is a frequent mistake; the sensor itself may be fine.
On some Volkswagen engines, the camshaft sensor shares a ground with other sensors, so a bad ground can mimic a sensor failure.
P1338 may be accompanied by other codes like P0340 or P0341, but this code specifically points to an open or short to B+ in the circuit, not a performance issue.

Can I keep driving with P1338?

If the engine starts and runs without noticeable performance issues, you may drive cautiously to a repair shop, but avoid aggressive acceleration or heavy loads. If the engine stalls, misfires severely, or fails to start, stop driving and have the vehicle towed to prevent further damage or safety risks.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Volkswagen vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.