Info - Tire Pressure Monitoring (TPM) System - System Messages

When diagnosing a customer concern related to the TPM system on the above vehicles, the following information may be helpful in determining if the concern is normal operation, related to a system fault or a low tire pressure(s). All of the above vehicles are equipped with a Driver Information Center (DIC) and may display one of three TPM system messages. It is very important to determine which message the customer is reporting.

Cause:

Scrolling through DIC information using steering wheel controls.

Correction:

None -- normal DIC message that precedes the individual tire pressures.

Explanation: 2005 model year utility vehicles with steering wheel controls have the ability of displaying the individual tire pressures on the DIC. The message "Tire Pressures" is the selection displayed on the DIC to view these pressures. This message does NOT illuminate the "Low Tire Pressure" light or set TPM system codes. A customer who is not familiar with the different DIC messages may perceive this normal system message as a system fault.

Cause:

One or more tire pressures are low when the message is present.

Correction:

Check and adjust tire pressures with tires cold.

Explanation: The DIC will display a "Check Tire Pressure" message on the DIC and illuminate the Low Tire light in the instrument cluster when any road tire pressure is lower than 25% of the placard value displayed on the tire pressure label. The "Check Tire Pressure" message does not indicate a system fault. The cause of a "Check Tire Pressure" message is most likely a low tire pressure. Vehicles that display this message are operating properly and tire pressures should be accurately adjusted (cold) to avoid the message and light.

Cause:

Various system faults.

Correction:

Follow diagnostics provided in Service Information.

Explanation: The DIC will display a Service Tire Monitor Message and illuminate the tire light in the IPC when a system fault is detected. TPM DTC's will also be set when this message is displayed. Normal diagnosis using Service Information should be performed when the Service Tire Monitor message is displayed.

Information About Setting Tire Pressures:

It is very important to set tire pressures to the placard value when the tires are cold. It is also very important to use an accurate tire pressure gauge when adjusting cold tire pressures. The rule of thumb is that tire pressure will rise approximately 6.9 kPa (1 psi) for every 5.6°C (10°F) temperature increase.

Consider the following example:

A customer comments that a message and light are displayed when the vehicle is first driven. The message and light goes out after the vehicle is driven. The customer is unsure of which message was displayed. The technician finds no codes in the TPM system and tire pressures appear to be only slightly lower than specifications. The customer believes they have properly set tire pressures to the 206 kPa (30 psi) specification displayed on the tire pressure label.

This condition is most likely caused by a tire pressure which is just below the 25% low point when the tires are cold. As the tire warms up (during driving) the tire pressure rises and is within the acceptable operating range.

In our example above, the true cold tire pressure may be less than expected due to the following controllable factors:

In this example, the "Check Tire Pressure" message will be displayed until the tire warms up during driving. The customer will see a message and a light until tire pressure exceeds 155 kPa (22.5 psi). This TPM system is operating properly but will still be a concern to a customer.