OBD-II trouble code
P0338: Crankshaft Position Sensor "A" Circuit High
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
- $200 – $400 (crankshaft position sensor replacement)
- DIY difficulty
- Intermediate DIY
Browse every code in P0300–P0394, or start from the full code library.
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 reading can be a signal wire shorted to voltage, a wiring fault that biases the circuit high, or a sensor driving its output high. Series resistance in a connector does not by itself raise the signal. On some module inputs an open signal line sits near supply; the wiring diagram says whether this input is biased that way. 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
- Open or high-resistance connection in the signal circuit — on some module input designs that leaves the line sitting near supply rather than being pulled down, so check the wiring diagram for how the input is biased before reading anything into the level
- 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 the sensor output during cranking and compare the level with the published spec for this sensor. Before anyone cranks, route the leads clear of the belt, pulleys, and cooling fan and keep hands and sleeves out of them. The engine may fire rather than just turn over.
- 5.Check the signal circuit for a short to voltage and for an open, using the bias the wiring diagram shows. Do not treat connector resistance as proof the signal was pulled high.
- 6.Replace the sensor only after the wiring, connector, and supply circuits all check out.
Repair cost
$200 – $400 (crankshaft position sensor replacement)
Crankshaft position sensor replacement, parts plus labor. This $200–$400 range is that sensor replacement. RepairPal's national average for the crankshaft position sensor is about $230–$335, and the listed vehicle examples run about $205–$375. A chafed wire, a connector repair, or a short to voltage is wiring labor and is not included in this sensor price. Prove the short to voltage before the sensor is condemned.
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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.