P0338: Crankshaft Position Sensor A Circuit High (Meaning, Causes, Fixes)
What P0338 means
The crankshaft position sensor (CKP) reports engine speed (RPM) and crankshaft position to the engine computer (PCM), which uses it to time the spark and fuel delivery. It sits a few thousandths of an inch from a toothed reluctor ring on the crankshaft, and the teeth passing the sensor create a voltage pattern the PCM reads. OBD-Codes.com explains that the PCM constantly compares the crank signal with the camshaft sensor signals, and that P0338 is stored when the crank sensor's input voltage stays too high over a set period of time. RepairPal describes the code more broadly, saying it sets when the PCM detects an irregular signal or no signal, and notes that on older vehicles the sensor may be built into the distributor. P0338 is the 'high' code for crank sensor 'A'; P0335 is the general circuit fault, P0336 is range/performance, P0337 is a low signal and P0339 is an intermittent signal. The two sources list somewhat different causes: OBD-Codes.com adds an overcharging alternator affecting the PCM, while RepairPal adds a broken tone ring.
Severity: can I keep driving?
Stop and fix promptly
Treat this as serious. RepairPal rates P0338 'Urgent', and OBD-Codes.com calls it severe: a no-start will likely come with it, and even if the engine starts and runs there is a high risk of a no-start soon. Don't count on the car until it's fixed.
Common symptoms
- Check engine light on
- Engine won't start
- Tachometer shows no RPM while the engine is cranking
- Hesitation on acceleration
- Poor engine performance
- Worse fuel economy
Likely causes
Roughly most to least common, based on the sources below. Your vehicle may differ.
- Failed crankshaft position sensor
- Open or shorted wiring to the crank sensor
- Corroded connector, or one soaked with oil, coolant or power steering fluid
- Broken tone ring (reluctor ring) on the crankshaft (listed by RepairPal)
- Alternator overcharging and upsetting the engine computer (listed by OBD-Codes.com)
- Faulty engine computer (PCM) or a PCM programming error (less common)
Diagnostic steps you can do
Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.
- Read all stored codes and freeze-frame data and write them down; it helps if the fault turns out to be intermittent.
- Look over the crank sensor wiring and connector. OBD-Codes.com points out that engine oil, coolant or power steering fluid can break down wire insulation and cause shorts or opens, so look closely at anything that's been soaked.
- Crank the engine while watching the tachometer or the RPM reading on a scan tool. No RPM while cranking points to a missing crank signal.
- Because OBD-Codes.com lists an overcharging alternator as a cause, check charging voltage at the battery with the engine running and compare it to your vehicle's spec.
- With the connector unplugged, check for the reference voltage (often 5 volts, but confirm your vehicle's spec) and a good ground at the sensor connector.
- If you have the service manual's resistance spec, test the sensor with a multimeter and replace it if it's out of spec. Specs vary by vehicle, so don't use a generic number.
Typical fixes
- Repair open or shorted wiring, or clean or replace a corroded or fluid-damaged connector
- Replace the crankshaft position sensor if testing shows it has failed (RepairPal lists this as the common repair; OBD-Codes.com notes some manufacturers recommend replacing crank and cam sensors as a set)
- Repair the charging system if the alternator is overcharging
- Replace a broken or damaged tone ring
- Check for technical service bulletins for your vehicle
- Have the PCM tested, reprogrammed or replaced only after the sensor, wiring and charging system check out
Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.
🛠 When to call a pro
- The engine won't start and you can't confirm the sensor's power, ground and signal yourself
- You've replaced the crank sensor and the code came back
- Checking the sensor's waveform properly needs an oscilloscope and wiring diagrams
- The tone ring is suspected, since reaching it usually means major disassembly
- A PCM fault or programming error is suspected
Where to buy
Plain search links. Always match parts to your exact year, make, model and engine.
FAQs
Can I drive with P0338?
It's risky. RepairPal rates it 'Urgent', and OBD-Codes.com says a no-start will likely come with it, and even if the engine runs there is a high risk of a no-start soon. Get it diagnosed before relying on the car.
Will a new crankshaft sensor fix P0338?
Often, since RepairPal lists sensor replacement as the common repair, but both sources also list wiring problems, and they add a broken tone ring (RepairPal), an overcharging alternator and a faulty PCM (OBD-Codes.com). Check the connector, wiring, reference voltage, ground and charging voltage before replacing the sensor.
What's the difference between P0337 and P0338?
Both are for crankshaft position sensor 'A'. OBD-Codes.com defines P0337 as a lower-than-expected input voltage and P0338 as an input voltage that stays too high. RepairPal uses the same 'irregular signal or no signal' description for both.
Why would the car crank but not start with P0338?
The PCM needs the crank sensor signal to time the spark and fuel injection. Without a usable signal it may not fire the engine, which is why OBD-Codes.com lists no RPM on the tachometer while cranking as a symptom.
Sources
Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.