1996 Subaru Legacy Tire Pressure Monitor Lamp Diagnosis Cost

Vehicles with the added benefit of tire pressure monitoring are able to tell the driver when the air pressure in a tire is too high, too low, and, in some vehicles, what the exact tire pressure is at all times. Manufacturers use sensors in the wheels to communicate wirelessly to the tire pressure monitoring system control module, and this module will illuminate the warning light when there is a tire air pressure issue. When the light comes on, diagnosis with a scan tool is only required if the air pressure is correct at the time the warning lamp appears while driving.

The tire pressure monitoring system (TPMS) control module will receive information from the tire pressure monitoring sensors at all times the vehicle is on. In most vehicles, the only purpose of the TPMS control module is to illuminate the TPMS warning light when the tire is under or overinflated. This makes diagnosing the system very easy with the right diagnostic scan tool.

The only symptoms requiring diagnosis for the tire pressure monitoring system warning lamp is if the warning lamp has illuminated while the tires have correct air pressure, or if the air pressure for the tires is out of specification and the warning lamp is off. This is because the overwhelming majority of cases where the TPMS lamp illuminates is due to the change in ambient temperature.

The TPMS warning light comes on all the time, but that does not mean it should be ignored. The light is designed to give you fair warning of deflation before damage is done to the tire or wheel, and to prevent unsafe driving when a tire goes flat. Anytime the light comes on, pull over and check the air pressure immediately when it is safe to do so.

As stated before, this occurs all of the time. In fact, this may be the most commonly seen warning light on the instrument cluster, but that does not mean it needs to be diagnosed. In fact, in nearly all cases the light will go off a few minutes after adjusting the air pressure in all four or six tires. This leaves a relatively small number of times where the TPMS warning lamp must be diagnosed to identify why it will not come on or turn off. Again, this is common, especially if the roads local to the vehicle have potholes and bumps.

After checking the air pressure, the technician will need to connect a diagnostic scan tool to test the wheel sensors first. In some vehicles, the sensors will not set an OBD-II code directing the technician to the faulty tire pressure sensor, and those must be checked manually. The tires can be inflated and deflated one at a time, and the sensor that does not register the change is faulty. However, if sensors fail to communicate with the control module or the control module is unresponsive, the control module will be diagnosed separately.

We always recommend contacting the repair center where the tires were last installed. Although the tire pressure sensors are fairly inexpensive, it is best to use the warranty if purchased.

It is essential to understanding where to locate the tire pressure information for the vehicle you drive in the event that you need to check, inflate, or deflate the tires. The information is likely posted on the driver door frame, inside the fuel tank lid, or in the owner's manual. Inflating a tire to the maximum allowable limit printed on the sidewall will be incorrectly overinflated every time.

Checking the air pressure in the tires is something anyone can do, and this solves the majority of issues arising with the TPMS warning lamp However, if a tire goes flat without the TPMS warning light being displayed, or the warning lamp does not turn off with correct pressure, diagnosis will need to be performed with a professional scanner.