What Does P0321 Mean?
The ignition/distributor engine speed input signal is present but falls outside the expected range or shows erratic performance characteristics. The PCM is receiving an RPM signal, but it is inconsistent, noisy, or does not match expected patterns for the operating conditions. The driver may notice rough running, intermittent stalling, or surging at various RPMs.
Common Causes
30%
Intermittent crankshaft position sensor failure with signal dropout under certain conditions
25%
Damaged crankshaft reluctor ring causing irregular pulse spacing
20%
Excessive CKP sensor air gap due to sensor movement or reluctor wheel wear
15%
Electromagnetic interference from nearby ignition components or corroded shielding
10%
Worn distributor shaft bushings causing wobble and inconsistent pickup signal
Diagnostic Steps
1
Monitor the engine RPM PID while driving at various speeds — look for sudden drops, spikes, or fluctuations that don't correspond to actual engine speed changes.
2
Capture the CKP sensor waveform with an oscilloscope at idle and at 2,500 RPM — verify uniform pulse amplitude and spacing. Flag any pulses that are significantly different in height or width.
3
Inspect the crankshaft reluctor wheel through the sensor bore or inspection port for cracks, debris accumulation, or damaged teeth.
4
Check the CKP sensor mounting torque and verify the air gap is within specification. A loose sensor can vibrate and cause intermittent range/performance issues.
5
Wiggle-test the CKP sensor connector and wiring while monitoring the RPM signal live to check for intermittent connection problems.
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
The ignition/distributor engine speed input signal is present but falls outside the expected range or shows erratic performance characteristics. The PCM is receiving an RPM signal, but it is inconsistent, noisy, or does not match expected patterns for the operating conditions. The driver may notice ...
The most common cause of P0321 (Ignition/Distributor Engine Speed Input Circuit Range/Performance) is: Intermittent crankshaft position sensor failure with signal dropout under certain conditions
Typical repair costs for P0321 range from $100 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle may stall intermittently, which could be dangerous in traffic. Drive cautiously and avoid highway driving if possible. The engine may run rough or hesitate. Have this repaired soon to avoid the risk of a stall in an unsafe situation.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0321 to identify the root cause.
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Quick Info
Category
Powertrain
System
Ignition System / Engine Management
Difficulty
Type
Generic (SAE)
Recommended Tools
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