P0297 is an OBD-II fault code indicating the Powertrain Control Module (PCM) has detected a vehicle overspeed condition. This means the engine RPM is higher than what the calculated vehicle speed should allow, suggesting the vehicle is traveling faster than the engine's power output should permit or the PCM is receiving erroneous speed data. The code is typically triggered when vehicle speed exceeds a manufacturer-defined threshold, often due to drivetrain slippage or sensor malfunction.
The VSS sends incorrect high-speed signals to the PCM, causing it to interpret the data as an overspeed condition even when the vehicle is stationary or moving slowly.
This sensor monitors transmission output shaft speed; if it malfunctions, it can send erratic or falsely high speed data to the PCM.
When the transmission slips, engine RPM can increase without corresponding vehicle speed increase, triggering the overspeed code.
Damaged, corroded, or loose wiring/connectors for speed sensors can cause intermittent or false high-speed signals.
Modified ECM tunes that alter speed governors or raise RPM limits can cause this code to set under certain conditions.
Rarely, the PCM itself may misinterpret sensor data or have a software glitch; this is the least likely cause and should be ruled out only after all other possibilities are exhausted.
It depends on the underlying cause. If caused by a sensor fault, the vehicle may still be driveable but may exhibit reduced power. If transmission slipping is the cause, continued driving could cause transmission damage. Have it diagnosed promptly.
Almost never. The PCM is rarely the cause of P0297. Many shops incorrectly recommend PCM replacement as a first step, but this is usually unnecessary and wasteful. The actual cause is almost always a sensor or transmission issue.
Yes. If the vehicle speedometer is malfunctioning or has been modified (such as with a speedometer healer for different tire sizes), it can cause the PCM to receive incorrect speed data and set the overspeed code.
Yes. Some aftermarket tunes that modify speed governors, remove factory speed limiting, or alter transmission shift strategies can cause this code to trigger, especially under wide-open throttle conditions.