P0337 Code: Crankshaft Position Sensor A Circuit Low
The crank sensor signal line is stuck near 0 volts, usually a wire shorted to ground. Often a no-start.
Stop driving
Don't drive it. A short to ground is often a wire rubbed through against the block or a bracket, and it can cut the engine the next time the harness moves over a bump. If the car won't start, tow it; if it does start, the short is intermittent and can return at speed.
At a glance
Severity: High
- Meaning
- Crankshaft Position Sensor A Circuit Low
- System
- Ignition & Misfire · Powertrain
- Safe to drive?
- No — stop driving
- Typical repair cost
- $75–$620
- DIY difficulty
- Moderate
On a three-wire Hall-type crank sensor, the engine computer holds the signal line at about 5 volts through an internal pull-up, and the sensor yanks it to ground each time a tooth passes. A healthy line therefore flickers between roughly 0 and 5 volts hundreds of times per second. P0337 means the computer sees that line sitting below its low threshold and not switching, as if something is clamping it to ground. With a two-wire magnetic (inductive) sensor, some computers log the same code when the AC output is far too small, for example from an open winding. Either way the computer has no usable crank reference, so most engines lose spark and injection instantly.
How to read P0337
- P Powertrain
- 0 Generic (SAE)
- 3 Ignition / misfire
- 37 Specific fault
Symptoms
- Cranks at normal speed but never fires, with the tachometer needle flat on zero
- Engine cuts out abruptly over a pothole, speed bump or during a sharp turn
- Several sensor codes at once, such as MAP or throttle position low, alongside P0337
- No spark at the plugs and no injector pulse while cranking
- Check-engine light on, often with P0335 stored as well
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Signal wire rubbed through against the block, a bracket, the starter or an exhaust heat shield
- Crank sensor shorted internally, often after its housing cracked and let in oil or water
- Shared 5-volt reference dragged to ground by another shorted sensor (cam, MAP, A/C pressure)
- Corroded connector or pushed-back pin bridging signal to ground
- Magnetic sensor with an open or failing winding producing almost no output
- Rodent damage to the engine harness
- Engine computer input circuit fault
Diagnosis step by step
Read every stored code before touching anything
If P0337 is alone, focus on the crank sensor circuit. If low-voltage codes for the MAP, throttle position or fuel tank pressure sensors appeared at the same moment, the shared 5-volt reference is being pulled down and the crank sensor may be innocent.
Tools: OBD-II scanner
Do the unplug test on the signal pin
Key on, engine off, disconnect the crank sensor and measure the harness signal pin to battery negative. It should rise to about 5 volts from the computer's pull-up. If it now reads 5 volts, the sensor itself was pulling the line down and is shorted; if it stays near 0 volts with the sensor unplugged, the wire or the computer is holding it low.
Tools: Multimeter
Check the reference and ground pins
On the same unplugged connector, the reference pin should show about 5 volts (12 on some engines) and the ground pin should read under 0.1 volt against battery negative. A reference of 0 to 1 volt points to a short elsewhere on the shared supply.
Tools: Multimeter
Find a shorted neighbor on the shared reference
With the multimeter on the crank sensor reference pin, unplug the other sensors fed from the same 5-volt circuit one at a time. The moment the voltage jumps back to 5 volts, the sensor you just disconnected is the one shorting it.
Tools: Multimeter
Resistance-check the signal wire to ground
Disconnect the battery and the computer connector, then measure from the signal wire to engine ground. It should read open (megohms). A few ohms or a few hundred ohms means the insulation is broken somewhere along the run; flex the harness section by section until the reading changes.
Tools: Multimeter
Trace the harness route
Follow the wire from the sensor toward the computer and look where it passes the oil pan rail, starter, bellhousing, engine mount and exhaust pipe. Shiny copper, a melted loom or chewed insulation marks the spot. Repair with solder and heat-shrink, then clip the harness away from the rubbing point.
Tools: Flashlight, Pliers
Test a two-wire magnetic sensor
Measure winding resistance against the spec (often several hundred up to about 1,500 ohms), then from each pin to the metal body, which must read open. Replace the sensor if it is open, far out of range or leaks to its body, and confirm cranking rpm on the scan tool afterward.
Tools: Multimeter
Where the parts are
- 1Ignition coil
- 2Spark plug
- 3Fuel injector
- 4Camshaft sensor
- 5Crankshaft sensor
- 6Engine computer (ECM)
- 7Intake manifold
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Repair chafed or shorted sensor wiring | No | $120–$400 |
| Replace crankshaft position sensor (easy access) | Yes | $140–$330 |
| Replace crankshaft position sensor (under intake, behind starter or at bellhousing) | No | $280–$620 |
| Replace another sensor that is shorting the shared 5-volt reference | Yes | $80–$300 |
| Tow to a shop | No | $75–$200 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Emissions / smog test impact
Will fail
A car with P0337 stored and the check-engine light on fails an OBD emissions test, and with a hard short it won't even run long enough to be tested. After the repair, drive several warm-up cycles so the misfire and other monitors report ready.
Frequently asked questions
Does 'circuit low' mean the sensor is getting weak?
Usually not. It describes the voltage the computer sees on the signal wire, not the sensor's health. The line is stuck near ground, which most often comes from a damaged wire or a short inside the sensor, not from gradual wear.
Why does the engine die exactly when I hit a bump?
A wire that has rubbed through its insulation can touch metal only when the engine rocks on its mounts or the harness flexes. Each contact pulls the signal to ground and the engine loses spark instantly. That pattern is a strong pointer to a chafed harness rather than a failed sensor.
Can a bad MAP or A/C pressure sensor really cause a crank sensor code?
Yes, on engines where several sensors share one 5-volt supply from the computer. If one of them shorts internally, the whole supply collapses and each sensor on it can report low. Unplugging them one by one while watching the reference voltage finds the culprit in minutes.
Should I just replace the crank sensor first?
Do the two-minute unplug test first. If the signal pin rises to about 5 volts with the sensor disconnected, the sensor is the problem and replacement is justified. If it stays at 0 volts, a new sensor won't fix anything.