P0339
Crankshaft Position Sensor A Circuit High Input
Powertrain Ignition System Crankshaft Position Sensor Circuit 🟡 Moderate — Fix within a week
💬
What This Actually Means
In plain language — no jargon

The crankshaft position sensor is sending a voltage signal that's too high to the engine computer, like a radio stuck on maximum volume. The ECU can't properly read engine timing, which disrupts ignition and fuel injection.

⚡
Symptoms You May Notice
3 known symptoms for this code
Engine won't start or starts intermittently
Check Engine Light illuminated
Rough idle and stalling at stops
🔬
Embedded Systems Insight
What the ECU/ECM is actually computing

The ECM monitors the analog voltage output from the crankshaft position sensor (CKP), which typically fluctuates between 0.5V and 4.5V as the crankshaft rotates. When voltage remains consistently above the upper threshold (usually >4.8V), the ECM detects a circuit high condition and triggers P0339.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
CKP Sensor Voltage 0.5V to 4.5V (varying with RPM) Above 4.8V continuously
Signal Pattern Regular pulse frequency matching crankshaft rotation No valid signal or stuck high signal
🔧
Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Wiring harness and connectors
Inspect CKP sensor connector for corrosion, loose pins, or damaged wires; clean or reseat connections.
2
Crankshaft Position Sensor
Unplug the sensor from its location near the crankshaft pulley, visually inspect for damage, and test with a multimeter or replace if faulty.
3
Engine Control Module (ECM) wiring
Check ECM connector pins for corrosion or bent terminals; clean and reseat if needed, or replace ECM if internal failure is suspected.