P0389 indicates the Powertrain Control Module (PCM) is receiving an intermittent or erratic signal from the crankshaft position sensor B. This sensor monitors engine speed and crankshaft position for proper ignition timing and fuel injection control. When the signal drops out or becomes unreliable, the code is set.
The sensor itself is the most common cause of intermittent failures due to internal wear, contamination, or thermal stress.
Damaged, chafed, or corroded wiring between the sensor and PCM, including loose or oxidized connector pins.
Loose or corroded ground connections, or issues with the sensor's power supply circuit causing intermittent signal dropout.
The tone ring or reluctor wheel on the crankshaft may be damaged, contaminated with debris, or have missing teeth, causing intermittent signal loss.
Loose sensor mounting, damaged mounting bracket, or improper sensor gap can cause intermittent signal problems.
A faulty PCM can cause this code, but this is rare and should only be considered after all other causes are ruled out.
No. The PCM is almost never the cause of P0389. While a faulty PCM can set this code, it is extremely rare. The overwhelming likelihood is a failing sensor, wiring issue, or electrical connection problem.
Driving is not recommended as the intermittent signal can cause the engine to stall unexpectedly or fail to start. The vehicle may run roughly or lose power, potentially creating a safety hazard.
Intermittent codes indicate the problem is not constant. This is typically caused by wiring that fails under certain conditions (heat, vibration, moisture), a sensor that is starting to fail, or loose connections that move during driving.
No. The crankshaft position sensor monitors crankshaft speed and position, while the camshaft position sensor monitors camshaft position. They serve different functions, though both can cause similar starting and running symptoms if they fail.