Backup for tire-pressure monitoring system
A computer includes a processor and a memory, and the memory stores instructions executable by the processor to, in response to a speed at which a vehicle is traveling exceeding a vehicle-speed threshold, determine a difference between wheel speeds of different wheels of the vehicle; and, in response to the difference exceeding a difference threshold, output a message indicating low pressure of a tire of one of the wheels.
1 . A vehicle system comprising:
a tire-pressure monitoring system of a vehicle; and
a computer of the vehicle, the computer comprising a processor and a memory, the memory storing instructions executable by the processor to:
determine that the tire-pressure monitoring system is inactive;
identify a fastest wheel speed and a slowest wheel speed of wheel speeds of at least four different wheels of the vehicle;
in response to a speed at which the vehicle is traveling exceeding a vehicle-speed threshold and the determination that the tire-pressure monitoring system is inactive, determine a difference between the fastest wheel speed and the slowest wheel speed; and
in response to the difference exceeding a difference threshold, output a message indicating low pressure of a tire of one of the wheels.
2 . The vehicle system of claim 1 , wherein the instructions further include instructions to, in response to the speed exceeding the vehicle-speed threshold and a steering angle of the vehicle being within a steering-angle range, determine the difference between the fastest wheel speed and the slowest wheel speed.
3 . The vehicle system of claim 2 , wherein the steering-angle range includes a straight-ahead steering angle.
4 . The vehicle system of claim 1 ,
further comprising a respective tire-pressure monitoring system for each tire; and
the instructions further include instructions to, in response to the speed exceeding the vehicle-speed threshold and at least one of the tire-pressure monitoring systems being inactive, determine the difference between the fastest wheel speed and the slowest wheel speed.
5 . The vehicle system of claim 1 , wherein the instructions further include instructions to, in response to the speed exceeding the vehicle-speed threshold for at least a time threshold, determine the difference between the fastest wheel speed and the slowest wheel speed.
6 . The vehicle system of claim 1 , wherein the instructions further include instructions to, in response to the speed exceeding the vehicle-speed threshold and a current operational mode of the vehicle being a first operational mode, determine the difference between the fastest wheel speed and the slowest wheel speed.
7 . The vehicle system of claim 1 , wherein the fastest wheel speed and the slowest wheel speed occur simultaneously.
8 . The vehicle system of claim 1 , wherein the difference is expressed as a proportion of the slowest wheel speed.
9 . The vehicle system of claim 1 , wherein the instructions further include instructions to, in response to the difference exceeding the difference threshold, set a flag in the memory.
10 . The vehicle system of claim 9 , wherein the instructions further include instructions to, in response to the vehicle starting with the flag set, output the message indicating low pressure of the tire.
11 . The vehicle system of claim 9 , wherein the instructions further include instructions to, in response to the difference being less than the difference threshold for at least a time threshold after setting the flag, remove the flag.
12 . The vehicle system of claim 1 , wherein the instructions to determine that the tire-pressure monitoring system is inactive include instructions to determine that the tire-pressure monitoring system is inactive in response to receiving a diagnostic trouble code indicating that the tire-pressure monitoring system is inactive.
13 . The vehicle system of claim 1 , wherein the instructions to determine that the tire-pressure monitoring system is inactive include instructions to determine that the tire-pressure monitoring system is inactive in response to not receiving data from the tire-pressure monitoring system for at least a time threshold.
14 . A method comprising:
determining that a tire-pressure monitoring system of a vehicle is inactive;
identifying a fastest wheel speed and a slowest wheel speed of wheel speeds of at least four different wheels of the vehicle;
in response to a speed at which the vehicle is traveling exceeding a vehicle-speed threshold and the determination that the tire-pressure monitoring system is inactive, determining a difference between the fastest wheel speed and the slowest wheel speed; and
in response to the difference exceeding a difference threshold, outputting a message indicating low pressure of a tire of one of the wheels.
15 . The method of claim 14 , further comprising, in response to the speed exceeding the vehicle-speed threshold and a steering angle of the vehicle being within a steering-angle range, determining the difference between the fastest wheel speed and the slowest wheel speed.
16 . The method of claim 14 , wherein the vehicle includes a respective tire-pressure monitoring system for each wheel;
the method further comprising, in response to the speed exceeding the vehicle-speed threshold and at least one of the tire-pressure monitoring systems being inactive, determining the difference between the fastest wheel speed and the slowest wheel speed.
17 . The method of claim 14 , further comprising, in response to the speed exceeding the vehicle-speed threshold for at least a time threshold, determining the difference between the fastest wheel speed and the slowest wheel speed.
18 . The method of claim 14 , further comprising, in response to the speed exceeding the vehicle-speed threshold and a current operational mode of the vehicle being a first operational mode, determining the difference between the fastest wheel speed and the slowest wheel speed.
19 . The method of claim 14 , wherein determining that the tire-pressure monitoring system is inactive includes determining that the tire-pressure monitoring system is inactive in response to receiving a diagnostic trouble code indicating that the tire-pressure monitoring system is inactive.
20 . The method of claim 14 , wherein determining that the tire-pressure monitoring system is inactive includes determining that the tire-pressure monitoring system is inactive in response to not receiving data from the tire-pressure monitoring system for at least a time threshold.