P0338 — Crankshaft Position Sensor A Circuit High Input

powertrain (engine/transmission)

Is it safe to drive?

Do not drive with an active P0338 P0338 can interrupt crank-position data and cause a stall or loss of power. Avoid driving if the engine runs rough, stalls, or shows an erratic tachometer until the fault is repaired and the code no longer returns.

Typical symptoms

  • The engine cranks but does not start while P0338 remains active.
  • The engine may start and then stall because Crankshaft Position Sensor A data is unreliable.
  • An intermittent P0338 can cause rough idle, hesitation, or misfires during normal driving.
  • The tachometer may show no engine speed or an erratic reading.
  • The check-engine light may illuminate with P0338 stored in the powertrain system.
  • The control module may enter a reduced-power or fail-safe mode because it cannot trust the crankshaft position signal.

Common causes

  • A failed Crankshaft Position Sensor A can generate an abnormally high output voltage and set P0338.
  • An open connection or high resistance in the Crankshaft Position Sensor A signal wire can leave the control module reading the circuit at excessive voltage.
  • The Crankshaft Position Sensor A signal wire may be shorted to a 5-volt, 12-volt, or battery voltage source.
  • Corrosion, damaged terminals, or a loose connector can create an intermittent high-input condition for P0338.
  • A defective sensor ground, reference circuit, or powertrain control module input can produce P0338 after external wiring faults are ruled out.

How to diagnose with an OBD scanner

  1. Confirm P0338 and capture freeze-frame data Connect an ELM327 adapter or use AIScanAuto to read stored codes, freeze-frame data, and engine RPM. Do not erase P0338 before recording the conditions under which it appeared.
  2. Inspect Crankshaft Position Sensor A wiring Use service information to locate Crankshaft Position Sensor A, then inspect its connector, signal wire, ground, and nearby harness routing. Look for separated terminals, corrosion, oil intrusion, chafing, or a wire touching a power circuit.
  3. Measure the signal during cranking With a digital multimeter or oscilloscope, measure the specified Sensor A circuit with the key on and while the engine cranks. A Hall-effect sensor should produce a controlled square wave, while a variable-reluctance sensor should produce alternating pulses. Compare the observed voltage and waveform with the manufacturer specification.
  4. Isolate the sensor from the control module circuit Follow the service-manual circuit test to check for shorts to power or ground and excessive resistance. If the external circuit passes, test Crankshaft Position Sensor A and its reference and ground paths before considering a powertrain control module input failure.
  5. Repair and verify the P0338 condition Repair the damaged connector or wiring, or replace Crankshaft Position Sensor A if it fails the specified test. Clear P0338 and related codes with the scanner, restart the engine, confirm stable RPM data, and road-test only if the engine runs consistently.

Approximate repair cost

A typical independent-shop estimate for diagnosing and repairing P0338 is $150 to $600, depending on sensor type, accessibility, and whether the wiring or connector needs repair. Figures are estimates and vary by region.

Common questions

What does P0338 mean on this vehicle?

P0338 means the control module is detecting abnormally high voltage on the Crankshaft Position Sensor A signal circuit.

Can I drive with a crankshaft position sensor high-input code?

Driving with an active P0338 is not recommended because an intermittent high signal can cause misfire, stall, or loss of engine power.

Does P0338 always require Crankshaft Position Sensor A replacement?

No. P0338 can also come from a shorted or open wire, a damaged connector, a bad ground, or a control-module input problem, so testing should precede replacement.

Why can P0338 appear even when the engine starts normally?

The crankshaft position voltage may briefly exceed the allowed range because of a loose terminal, damaged harness, or intermittent sensor fault that clears once the engine runs.

The crankshaft position sensor plays a critical role in your engine's operation. It monitors the exact position and rotational speed of the crankshaft, feeding that information to the engine control module dozens of times per second. Without this data, the ECM cannot determine when to fire the ignition coils or inject fuel, so the engine simply cannot run.

P0338 triggers when the ECM receives a voltage signal from the crankshaft position sensor circuit that exceeds acceptable limits. Specifically, "circuit high input" tells you that the voltage on the sensor's signal wire is sitting near battery voltage when it should be varying between roughly zero and five volts as the reluctor wheel teeth pass by the sensor tip. This reading tells the computer that something is fundamentally wrong with the electrical circuit—not just a marginal signal, but a clear fault condition.

The ECM sets P0338 after comparing live sensor data against its programmed thresholds, typically requiring the fault to appear across multiple drive cycles before illuminating the check engine light. When this happens, the stored freeze frame captures the engine's operating conditions at the moment of failure—rpm, load, temperature, and speed. Reviewing that snapshot before diving into repairs often points you toward the root cause much faster than randomly replacing parts.

Symptoms of P0338

P0338 produces symptoms that directly reflect the crankshaft sensor's importance to engine operation:

  • Check Engine Light illuminated on the dashboard
  • Engine cranks normally but fails to start
  • Intermittent starting problems, particularly after the engine is hot
  • Tachometer needle stays dead or drops to zero during cranking attempts
  • Unexpected stalling while driving with no prior warning

Common Causes

The underlying issues that produce P0338 range from simple wiring problems to complete sensor failure:

  • Damaged sensor wiring or loose connector causing an intermittent short
  • Failed crankshaft position sensor pulling the signal line permanently high
  • Signal wire shorted directly to battery positive somewhere in the harness
  • Open ground return circuit for the crankshaft position sensor
  • Incorrect air gap between the sensor tip and reluctor wheel
  • Damaged or bent reluctor wheel teeth on the crankshaft
  • ECM internal processing fault (least common)

How to Diagnose P0338

Follow this systematic approach to isolate the problem without wasting money on guesswork:

  1. Connect an OBD2 scanner and verify P0338 is stored in the ECM memory. Record the freeze frame data immediately—this tells you exactly what the engine was doing when the fault occurred.
  2. Pull all stored diagnostic trouble codes from the vehicle. Related codes in the same circuit often reveal whether the problem originates in the sensor itself, its wiring, or the ECM. Check manufacturer technical service bulletins for your specific make and model, as factory-known issues sometimes have published solutions or software updates.
  3. Perform a thorough visual inspection of the crankshaft position sensor wiring harness and electrical connector. Look for chafed insulation, corroded pins, broken wires at the connector strain relief, or signs of previous repairs that may have failed.
  4. Disconnect the crankshaft position sensor and measure voltage at the harness side of the connector. If battery-level voltage appears with the sensor unplugged, you have a short-to-power condition in the wiring harness itself. If the voltage drops to near-zero with the sensor disconnected, the component itself is likely failed.
  5. Monitor the rpm parameter ID while an assistant cranks the engine. No rpm signal whatsoever confirms a circuit problem—the sensor, wiring, or ECM input.
  6. Remove the sensor and inspect the tip for metal debris, damage, or chips. Check the reluctor wheel for bent, missing, or damaged teeth that could affect the signal.
  7. Clear the code, drive the vehicle through a complete drive cycle that reproduces the freeze frame conditions, and verify P0338 does not return.

Repair Options and Costs

Depending on which component is actually faulty, here are the typical repair approaches:

  • Sensor wiring repair or connector replacement: $80–$250
  • Reluctor wheel replacement: $400–$900
  • Crankshaft position sensor replacement: $150–$400

Total Repair Cost

P0338 repair typically runs between $80 and $900 depending on what needs fixing. Wiring repairs or connector issues represent the least expensive scenario, while reluctor wheel replacement commands premium labor costs due to accessibility—on many engines, this component lives behind the harmonic balancer or at the transmission bellhousing. The sensor itself falls in the middle range for both parts and labor. The key money-saving step remains accurate diagnosis before purchasing any components.

Driving Safety Verdict

Do not continue driving with this code active. A faulty crankshaft position sensor can cause your engine to stall without warning, leaving you stranded or, worse, disabled in traffic. The sudden loss of power affects power steering and braking assistance, creating a hazardous situation at any speed. Repair P0338 before driving the vehicle further.