The OBD2 code P0297 indicates a “Vehicle Overspeed Condition,” suggesting that the vehicle has exceeded a predetermined speed limit set by the manufacturer. While it might seem like a straightforward issue related to driving habits, this code can sometimes uncover underlying problems affecting vehicle performance, ranging from sensor malfunctions to more serious mechanical issues.
P0297 quick overview
| Meaning | P0297: Vehicle Overspeed Condition |
| Is it serious? | Yes, it can indicate potential safety issues or underlying mechanical problems. |
| Possible causes | – Faulty vehicle speed sensor – Malfunctioning throttle body or accelerator pedal sensors – Issues with the vehicle speed control module – Aftermarket modifications affecting speed regulation |
| How to diagnose? | Check the vehicle speed sensor for malfunctions or wiring issues. Inspect the throttle body and accelerator pedal sensors for proper functionality. Test the vehicle speed control module for faults. Verify speedometer accuracy against a GPS reading. Look for aftermarket modifications that could affect speed regulation. |
P0297 Meaning
When you see the P0297 code, it means your car thinks it’s going faster than it’s supposed to, according to the computer that runs the car. This might sound like something that happens if you’re speeding, but it can also mean there’s a glitch in the system that tells your car how fast it’s going.
It could be a problem with a sensor that measures speed or even with the parts of your car that control how fast it goes. Fixing this issue is important not just to avoid speeding but to make sure your car is running right and safely.
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How to fix P0297 – learn from mechanics
I looked into P0297 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Ford
Vehicle Information 2006 Ford E-250 4.6L
Issue + Repair History
- Engine running rough at idle, feels like misfire.
- Only OBD2 trouble code: P0297.
- No previous repair history mentioned.
Other OBD2 Codes + Test Results
- Only the P0297 trouble code mentioned.
- No additional test results provided.
Mechanic Suggestions
- Use the scan tool to check for RPM drop while the engine is running to identify specific cylinders affected.
- Utilize Generic Functions, Mode 6, test 53 to diagnose misfires for each cylinder.
- Refer to Technical Service Bulletins (TSBs) for potential issues related to misfires, such as fouled spark plugs or injector problems.
Final Fix After performing diagnostics, it was found that cylinders 8 and 5 had no RPM drop. Both ignition coils and spark plugs were replaced, resolving the misfire issue.
Case #2: Ford
Vehicle Information 2010 Ford F-450 Super Duty XLT 6.4L
Issue + Repair History
- Vehicle shut off on the highway, followed by white smoke upon restart.
- Freeze frame data shows engine temperature at 203°F.
- Catalyst temperature readings show a significant difference between sensors 1 and 2.
- Live data indicates exhaust absolute back pressure sensor reading of 16PSI, with desired reading at 4PSI.
- No previous repair history mentioned.
Other OBD2 Codes + Test Results
- Trouble codes:
- P200E (Catalyst Overtemp)
- P0297 (Overspeed vehicle over 81 mph)
- Other test results:
- EGT sensors reading close during comparison.
- Exhaust back pressure readings: 16PSI (engine running), 12PSI (engine off).
Mechanic Suggestions
- Perform regeneration to clean out soot buildup in the DPF (Diesel Particulate Filter).
- Insert a manual probe to obtain a true back pressure reading, as elevated back pressure can indicate a clogged DPF or other issues.
- Consider altitude adjustments for absolute exhaust back pressure readings.
- Investigate the cause of white smoke, potentially indicating an over-fueling issue or external fuel source entering the cylinder or exhaust.
- Check DPF reading for restriction to assess the condition of the filter.
- Look for blow-by and conduct power balance or fuel trim checks to identify potential cylinder-related issues.
- Consider EGT sensor failure as a common issue, especially with intermittent failures.
- Perform power balance test and check for over-contributing cylinders, suspecting injector or compression issues if the truck is running rough.
- Monitor fuel trims for variances indicating faulty components.
Final Fix The vehicle was taken to the dealer, where it was diagnosed with a faulty turbo and a clogged DPF filter. Repairs were conducted accordingly, resolving the excessive emissions issue.
Case #3: Dodge
Vehicle Information 2015 Dodge Ram 1500 SLT 5.7L
Issue + Repair History
- Experiencing an overspeed condition without check engine light illumination.
- No previous repair history mentioned.
Other OBD2 Codes + Test Results
- OBD2 trouble code: P0297
- No additional OBD2 codes or test results provided.
Mechanic Suggestions
- Check the vehicle speed sensor for any malfunctions or wiring issues that could cause erroneous speed readings.
- Inspect the throttle body and accelerator pedal sensors for proper functionality and calibration.
- Test the vehicle speed control module for any faults that could lead to an overspeed condition.
- Check for any aftermarket modifications that could affect vehicle speed regulation.
- Verify the accuracy of the speedometer by comparing it with a GPS speed reading.
Final Fix After thorough diagnostics, it was found that the vehicle speed sensor was faulty, providing incorrect speed readings to the control module. The speed sensor was replaced, resolving the overspeed condition and restoring normal vehicle operation.
How to diagnose P0297
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Brief Explanation |
|---|---|
| Check the vehicle speed sensor | Ensure it’s providing accurate speed readings. |
| Inspect throttle body and accelerator pedal sensors | Verify they are functioning correctly and calibrated. |
| Test vehicle speed control module | Look for any faults that could lead to overspeed. |
| Compare speedometer to GPS speed | Confirm the accuracy of the vehicle’s speed reading. |
| Check for aftermarket modifications | Identify any changes that could impact speed regulation. |
In the service cases from a Ford E-250, Ford F-450 Super Duty, and Dodge Ram 1500, the P0297 code was triggered by different issues, from engine misfires and DPF clogging to a faulty vehicle speed sensor. These examples highlight the importance of thorough diagnostics to uncover and address the root cause of the overspeed condition, ensuring the vehicle operates safely and efficiently.
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)