P1635 Ford Code - Tire / Axle Ratio Out of Acceptable Range

Vehicles may experience issues like poor fuel economy, hesitation during acceleration, or incorrect speedometer readings.

This code is typically triggered when there is a mismatch between the tire size and axle ratio programmed into the vehicle's powertrain control module (PCM).

You can start by checking the tire size and axle ratio settings in the PCM to ensure they match the actual specifications of the vehicle. Additionally, inspecting the speed sensor and related wiring can help identify any issues.

If the issue is simply a matter of correcting the tire size or axle ratio settings in the PCM, it may be possible for a knowledgeable DIYer to address the problem. However, for more complex issues, professional diagnostic equipment may be needed.

Ignoring this code can lead to inaccurate speedometer readings, which can affect driving safety and potentially cause further damage to the vehicle's drivetrain components.

While the vehicle may still be operable with this code present, it is not recommended to ignore it, as it can lead to performance issues and inaccuracies in speed and mileage readings.

The cost of repairing this code can vary depending on the root cause of the issue. It may range from a simple adjustment of settings to more complex repairs involving sensors or wiring.

Resetting the PCM may temporarily clear the code, but if the underlying issue, such as a tire size or axle ratio mismatch, is not addressed, the code is likely to reappear.

While a faulty speed sensor can contribute to this issue, simply replacing the sensor may not always resolve the problem. It's crucial to diagnose the root cause accurately before proceeding with any repairs.

Regularly checking and ensuring that the tire size and axle ratio settings are correctly programmed into the PCM, especially after any modifications or upgrades, can help prevent this code from reoccurring.