What Does P0389 Mean?
The crankshaft position sensor B circuit is producing an intermittent signal. This means the sensor B output is cutting in and out, producing an unreliable position reference. Intermittent CKP faults are among the most challenging to diagnose because the fault may not be present during testing. The driver may experience random brief engine stumbles, occasional stalling, sporadic misfires, or intermittent rough idle that resolves on its own.
Safety Warning
Intermittent CKP sensor failures can cause sudden, unpredictable engine stalling. Because the fault is random, it could occur during highway driving or in an intersection. This is a serious safety concern. Minimize driving until diagnosed; if the engine stalls more than once, have the vehicle towed.
Common Causes
30%
Intermittent connection at the CKP sensor B connector due to worn, spread, or corroded pins
25%
CKP sensor B failing intermittently due to heat-related internal breakdown
25%
Damaged wiring with broken conductor that makes contact intermittently with vibration
10%
Loose sensor mounting allowing the air gap to vary with engine vibration
10%
Intermittent ECM connection or internal circuit fault on the sensor B input
Diagnostic Steps
1
Set up continuous data logging of CKP sensor B RPM PID and misfire counters. Drive the vehicle under varied conditions to capture the intermittent event. Note engine temperature, RPM, and load when the fault occurs.
2
Perform a thorough wiggle test on the entire CKP sensor B circuit while monitoring the oscilloscope waveform. Start at the sensor connector, work through the harness, and finish at the ECM connector. Any signal disruption during the test pinpoints the fault location.
3
Check the CKP sensor B connector pins with a pin-tension gauge or by inserting the mating terminal and checking for a secure fit. Spread or worn female terminals are a common cause of intermittent connections. Terminal tension should require moderate force to separate.
4
Verify the CKP sensor B mounting bolt is tight and the sensor is fully seated in the bore. Apply a small amount of thread-locking compound to the mounting bolt to prevent vibration-induced loosening.
5
Heat-test the sensor by running the engine until fully warm, then monitoring the waveform with an oscilloscope. Many intermittent sensor failures occur only at operating temperature. If the signal drops out when hot, replace the sensor.
6
Check the ECM connector pins for the CKP B circuit. Back-probe and verify a solid connection. Look for green corrosion or signs of water intrusion in the ECM connector.
Estimated Repair Cost
$100 - $550
Parts + labor, varies by vehicle and location
The crankshaft position sensor B circuit is producing an intermittent signal. This means the sensor B output is cutting in and out, producing an unreliable position reference. Intermittent CKP faults are among the most challenging to diagnose because the fault may not be present during testing. The ...
The most common cause of P0389 (Crankshaft Position Sensor B Circuit Intermittent) is: Intermittent connection at the CKP sensor B connector due to worn, spread, or corroded pins
Typical repair costs for P0389 range from $100 to $550, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Intermittent CKP sensor failures can cause sudden, unpredictable engine stalling. Because the fault is random, it could occur during highway driving or in an intersection. This is a serious safety concern. Minimize driving until diagnosed; if the engine stalls more than once, have the vehicle towed.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0389 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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