OBD-II trouble code
P0338: Crankshaft Position Sensor "A" Circuit High Input
The crankshaft position sensor circuit is reading too high — the voltage the PCM sees has climbed above its expected window, which typically points at a short to voltage, a wiring fault, or a failed sensor. As the mirror image of the low-input code P0337, it carries the same stakes: because the crank signal is the engine's master timing reference, a high-input fault commonly means no-start or stalling.
Quick facts
- System
- Powertrain
- Category
- Sensors / Timing
- Severity
- High severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $130 – $700
- DIY difficulty
- Intermediate DIY
What does P0338 mean?
P0338 is the 'circuit high input' member of the crankshaft position sensor 'A' family — the electrical opposite of P0337. The CKP sensor reads the toothed reluctor wheel on the crankshaft and reports engine position and speed, which the PCM uses to time spark and fuel and to detect misfires. P0338 sets when the voltage on that circuit stays above the expected range: the signal is pulled high or biased up beyond what a normal crank waveform should reach. It's a level complaint, distinct from P0336 (implausible pattern), P0335 (general circuit fault), and P0337 (level too low).
A high-input reading usually traces to the circuit being pulled toward voltage or to a sensor that's outputting incorrectly. The classic causes are a short to a voltage source in the signal wire (often where a harness chafes against a powered wire), a wiring fault that biases the circuit high, a corroded or damaged connector creating resistance that skews the reading, or a sensor that has failed in a way that drives its output high. On powered sensors, a problem in the supply or reference circuit can also push the signal above spec. Because the pattern isn't the issue — the level is — meter and scope testing of the circuit for shorts to voltage, biasing, and abnormal supply is the productive route.
The operational impact mirrors the other crank-circuit faults: with the timing reference out of usable range, the engine often won't start, starts and stalls, runs roughly, or cuts out without warning, and the tachometer may misbehave during cranking. It's not a code to rely on the car with. Diagnosis starts at the sensor connector — inspect for corrosion and damage, check the signal wire for a short to voltage, verify supply and ground on a powered sensor, and confirm the sensor's output level against spec before condemning it.
Common causes
- Short to a voltage source in the CKP signal wire, often from a chafed harness
- Wiring fault biasing the circuit above its normal range
- Corroded or damaged connector adding resistance that skews the reading high
- Failed CKP sensor driving its output high
- Supply or reference-circuit problem on a powered (three-wire) sensor
- Damaged insulation letting the signal wire contact a powered circuit
- Improper sensor or wiring after a previous repair
Symptoms
- Check engine light with P0338 stored
- No-start or hard-start condition
- Engine that starts then stalls
- Rough running or unexpected stalling while driving
- Erratic or zero tachometer reading during cranking
- Intermittent loss of spark or fuel
Diagnostic steps
- 1.Inspect the CKP sensor connector for corrosion, damage, and backed-out pins as a first, quick check.
- 2.Check the signal wire for a short to voltage — look closely where the harness could chafe against a powered wire.
- 3.On a powered sensor, verify supply voltage, reference, and ground are within spec, since a supply fault can bias the signal high.
- 4.Scope or meter the sensor output during cranking; a level that stays above spec confirms the high-input condition.
- 5.Test wiring continuity and resistance back to the PCM for faults that would skew the reading.
- 6.Replace the sensor only after the wiring, connector, and supply circuits all check out.
Repair cost
$130 – $700
A crankshaft position sensor replacement generally runs $150-$400 with labor, more where access is difficult. Repairing a short to voltage or a chafed wire, or fixing a connector, can be less but takes diagnostic time to locate. Powered-sensor supply faults are wiring labor rather than a part. As with the other crank-circuit codes, budget some diagnosis to separate a circuit fault from a failed sensor.
Estimate your repair
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Open the Repair Cost Estimator with crankshaft position sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.