Crankshaft Position Sensor A Circuit High Input
The P0338 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the crankshaft position sensor that is higher than the expected range. This sensor monitors engine speed and position for fuel injection and ignition timing. A high input can be caused by a faulty sensor, wiring issues, or a problem with the sensor's circuit.
1. Most Common Causes
- Short circuit of the crankshaft position (CKP) sensor wiring to battery voltage (B+)
- Excessive resistance or open circuit in the sensor ground wire
- Faulty crankshaft position sensor (internal failure)
- Corroded, damaged, or moisture-contaminated sensor connector or terminals
- Intermittent wiring harness failure due to chafing or excessive heat
- Rare issue: internal ECM/PCM failure (differential diagnosis)
2. Symptoms You Will Notice
- Engine may not start or stalls
- Check Engine Light illuminated
- Rough idle or misfires
- Reduced engine performance
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect sensor wiring and connector for damage or corrosion.
Step 3: Test sensor resistance and voltage output with a multimeter.
Step 4: Check for shorts to voltage in the sensor circuit.
Step 5: Replace sensor if faulty and clear codes.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The engine may stall or fail to start, leading to a potential accident.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, depending on vehicle make and model.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.