P0297

P0297 means the ECM observed the vehicle speed signal exceed the manufacturer's programmed maximum speed threshold — typically 100-150 mph for stock passenger cars, 85-90 mph for stock light trucks, and higher (155-186 mph or fully delimited) for performance vehicles and exotics. The code stores when speed exceeded the limit AND when the ECM intervened (fuel-cut, ignition-cut, or throttle-close) to bring speed back into range. Cheapest-first ladder: this is almost never an electrical fault — read the freeze-frame data first and confirm the actual recorded speed at the time of the code; if freeze-frame shows 110-150 mph, the code is doing its job and there's no diagnostic to perform beyond confirming the driver knows the vehicle hit its limiter. If freeze-frame shows an implausibly high speed (say, 250 mph on a Camry), the issue is a VSS (vehicle speed sensor) signal fault, an ABS wheel-speed sensor reading high, or a CAN-bus speed-message corruption — scan all four wheel-speed sensors during a low-speed test drive and confirm they all agree within 1-2 mph of each other and of the dash speedometer. Some platforms set P0297 spuriously when one wheel-speed sensor reads high due to a damaged tone ring or a magnetized sensor (metal shavings sticking to the sensor face). The expensive misdiagnosis on P0297: shops chase wiring on a code that was simply triggered by a driver hitting the speed limiter on an empty highway or at a track day — verify with the owner whether the vehicle has been driven beyond legal speeds before pulling parts. Clear the code, drive normally, and if it doesn't return, it was a one-time event.

Vehicle-specific patterns: any vehicle driven beyond its OEM-programmed speed limiter will set P0297 — the code is essentially a tattletale, not a fault. Common platforms: BMW M-cars (M3, M4, M5, M8) ship with a 155 mph limiter that's commonly removed via M Driver's Package or aftermarket coding, and when the limiter is reinstated the code sets aggressively; Mercedes-AMG vehicles share the same 155 mph factory limiter and the same code pattern. Ford Mustang GT/Shelby, Chevrolet Camaro SS/ZL1, and Dodge Challenger Hellcat/SRT see P0297 commonly at track days where customers hit the factory limiter (typically 150-160 mph on stock tires for safety). Exotics with delimited or higher-set limits (Porsche 911 Turbo, Lamborghini Huracan, Ferrari 488) still set P0297 if pushed beyond their programmed ceiling, which on some platforms is keyed to tire-speed-rating data. Modified vehicles with aftermarket tunes that increase the speed limiter while the ECM's secondary safety-check threshold remains stock will set P0297 because the safety threshold is below the new limiter — a tune-recheck at the tuner clears the disagreement. Estimated repair: $0 (no fault, driver-induced) to $400 (VSS or wheel-speed sensor replacement if actually electrical).