What Does P0386 Mean?
The ECM has detected that the crankshaft position sensor B signal is outside its expected range or performance parameters. The sensor is producing a signal, but the quality, amplitude, frequency, or pattern does not match what the ECM expects for the given operating conditions. This can cause subtle timing errors, intermittent misfires, and degraded fuel economy as the ECM compensates for the unreliable signal.
Common Causes
30%
Worn or weakened CKP sensor B producing low-amplitude output signal
25%
Excessive sensor-to-reluctor air gap due to sensor migration, bracket wear, or improper installation
20%
Partially damaged reluctor ring with worn or slightly chipped teeth
15%
High resistance in the CKP B signal circuit reducing voltage at the ECM
10%
Oil or metallic debris contamination on the sensor face or reluctor teeth
Diagnostic Steps
1
Using a dual-channel oscilloscope, compare the waveforms of CKP sensor A and sensor B simultaneously at idle and 2500 RPM. The amplitude, shape, and tooth-to-tooth consistency should be nearly identical between the two sensors.
2
Measure sensor B signal amplitude at various RPMs. For a magnetic sensor, amplitude should increase proportionally with speed (typically 0.5V at idle to 5V+ at 3000 RPM). Low amplitude at all speeds indicates a weak sensor or excessive air gap.
3
Verify the sensor air gap is within specification using a non-magnetic feeler gauge. If the gap has increased from the original installation, check the mounting bracket for wear or the sensor bore for debris preventing full insertion.
4
Measure total circuit resistance from ECM pins to CKP sensor B pins. The reading should closely match the sensor's internal resistance with less than 2 ohms additional from the wiring. Higher readings indicate a wiring issue.
5
Remove sensor B, clean the tip with brake cleaner, and inspect the reluctor ring teeth through the sensor bore. Look for excessive wear, partial tooth damage, or metallic debris buildup that could affect signal quality.
Estimated Repair Cost
$80 - $450
Parts + labor, varies by vehicle and location
The ECM has detected that the crankshaft position sensor B signal is outside its expected range or performance parameters. The sensor is producing a signal, but the quality, amplitude, frequency, or pattern does not match what the ECM expects for the given operating conditions. This can cause subtle...
The most common cause of P0386 (Crankshaft Position Sensor B Circuit Range/Performance) is: Worn or weakened CKP sensor B producing low-amplitude output signal
Typical repair costs for P0386 range from $80 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A range/performance issue means the sensor is partially working, so the risk of sudden stalling is lower than a complete failure. However, timing accuracy is compromised, which can cause misfires and potential catalytic converter damage over time. Schedule repair soon; the vehicle can generally be driven to a repair facility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0386 to identify the root cause.
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Quick Info
Category
Powertrain
System
Ignition / Engine Timing System
Difficulty
Type
Generic (SAE)
Recommended Tools
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