OBD-II Diagnostic Trouble Code
P0337 — Crankshaft Position Sensor A Circuit Low
P0337 means the ECM sees the crankshaft position sensor A signal voltage stuck below the expected range, which usually points to a short to ground or an open supply on a 3-wire Hall-effect sensor. On 2-wire magnetic sensors, it can indicate a very weak signal.
Severity 5/5
Truck-relevant
Stop now
Severity
Stop now — do not drive
Crankshaft Position Sensor A Circuit Low
Code
P0337
Category
Powertrain
Subsystem
Ignition
Truck-relevant
Yes
What this means for truckers
P0337 (Crankshaft Position Sensor A Low) — CKP shorted to ground.
Before you replace parts — try this first
P0337 on the Ignition system is most often signal wire shorted to ground from a chafed harness — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Crank-no-start, stalling, or the engine running on the camshaft backup signal with longer crank times and reduced power. The tachometer may drop out. Often comes with other low-voltage sensor codes if the 5-volt reference is shorted.
Common causes
- CommonSignal wire shorted to ground from a chafed harness ($100–$500)
- CommonFailed crankshaft position sensor ($150–$500)
- OccasionalLoss of 5-volt reference or sensor supply, often from another sensor shorting the shared reference ($100–$600)
- OccasionalCorroded or water-intruded connector ($80–$300)
- RareECM input fault ($1200–$3500)
How to fix
Check for 5-volt supply and good ground at the sensor connector with the key on
When to use: First step on 3-wire sensors
Inspect the harness for chafing against brackets, the block or the bellhousing and repair any shorts
When to use: When supply is fine but signal stays low
Unplug other sensors on the shared 5-volt reference one at a time to find a shorted sensor
When to use: When several low-voltage codes set together
Replace the crankshaft position sensor
When to use: When wiring and supply test good
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0300 — Random/Multiple Cylinder Misfire Detected
- → P0301 — Cylinder 1 Misfire Detected
- → P0302 — Cylinder 2 Misfire Detected
- → P0303 — Cylinder 3 Misfire Detected
- → P0304 — Cylinder 4 Misfire Detected
Frequently Asked Questions
Can I drive with code P0337?
No — P0337 is severity 5. Stop and tow if you're not near a service location. Continuing to drive can cause catastrophic engine damage. The cost of a tow ($300–800) is small compared to the cost of an engine rebuild ($15,000+).
How much does it cost to fix P0337 on a commercial truck?
Total repair cost ranges $80–$3500 depending on the root cause. The cheapest fix is usually the first one listed below — Signal wire shorted to ground from a chafed harness — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0337 fail a DOT inspection?
P0337 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P0337 and related codes?
P0337 is closely related to: P0300 (Random/Multiple Cylinder Misfire Detected), P0301 (Cylinder 1 Misfire Detected), P0302 (Cylinder 2 Misfire Detected), P0303 (Cylinder 3 Misfire Detected). These codes share the same subsystem (ignition) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0337 is set without the companions, the issue is more isolated.
How do I prevent P0337 from coming back after a repair?
For P0337 (Crankshaft Position Sensor A Circuit Low), prevention centers on the ignition system. Use OEM-spec injectors and spark plugs (gas). Address fuel quality issues immediately — bad fuel kills injectors. Cylinder balance test annually for early warning.