P0338
Crankshaft Position Sensor A Circuit High Input
When a vehicle powertrain module registers the fault code P0338, it points directly to an internal system malfunction identified as "Crankshaft Position Sensor A Circuit High Input". Operating your engine under this condition may degrade long-term fuel maps.
Driver's Summary
Your vehicle's computer logged P0338 after detecting a malfunction in the crankshaft position sensor a circuit high input system. On the road, this usually shows up as no start condition, engine misfires severely, mil illuminated. Stop driving as soon as it is safe to do so. This fault can lead to expensive secondary damage if left unaddressed.
Symptoms
No start condition, engine misfires severely, MIL illuminated
Common Causes
- Short to battery voltage in circuit
- Open ground connection for sensor
- Defective crankshaft position sensor
- Broken reluctor ring
How to Fix
- 1 Repair short to voltage
- 2 Fix broken ground wire
- 3 Replace crankshaft position sensor
- 4 Inspect and replace reluctor ring
Technical Explanation
The PCM triggers P0338 after its internal monitoring routine detects that a specific circuit or sensor has exceeded its acceptable operating range. The PCM monitors crankshaft rotational velocity via the CKP sensor at a resolution of individual tooth gaps on the reluctor ring. A combustion event in each cylinder produces a measurable acceleration spike; its absence or weakness is flagged as a misfire event within a 200-revolution or 1000-revolution test window. Once confirmed, the code is stored as a permanent DTC and the MIL is activated. The freeze frame snapshot — recording RPM, load, coolant temperature, and fuel trim at fault detection — is also saved and is critical for accurate diagnosis.
Is It Safe to Drive?
This fault carries real mechanical risk. The root causes — including short to battery voltage in circuit — can trigger a chain reaction of component failures if the vehicle continues to be driven. Have it towed or drive directly to a shop without delay.
Mechanic's Pro Tip
The most common mistake with P0338 is replacing the sensor without verifying the reference voltage and ground integrity first. Use a scan tool to monitor the sensor's live output; a truly failed sensor shows a stuck, flatlined reading — a sensor that fluctuates but reads slightly off usually indicates a wiring or vacuum issue, not a dead sensor. Always spray electrical contact cleaner on the connector pins before condemning the sensor.
Sensor: 150 - 350; Reluctor ring: 400 - 600