Tire Pressure Monitoring System (TPMS) - System Operation and Component Description

of each sensor based on the training (calibration) order. The BCM sends messages to the RTM by first sending the information along the HS-CAN1 to the GWM which then sends the information to the RTM along the MS-CAN.

The diagnostic scan tool is useful in diagnosing TPMS concerns and may be used to verify the accuracy of the tire pressure data transmitted by the TPMS sensors. This is accomplished by comparing the BCM tire pressure PID data to the actual tire pressure using a digital tire pressure gauge.

It is not necessary to train the sensors after a tire rotation on vehicles with the same front and rear tire pressures however, the BCM cannot recognize the sensor identifiers have been moved to different positions and retains the original position information for each sensor.

Wheel Rotation and Sensor Training Techniques

Training known good sensors from another vehicle can help determine whether the concern is with a sensor or the RTM. This technique cannot help determine whether the concern is due to RFI as some RFI source could be preventing the RTM from receiving the tire pressure status from the known good sensors as well as the original sensors.

If the RTM in the suspect vehicle cannot train any of the original sensors and, likewise, cannot train known good sensors from another vehicle, then the concern is with the module or RFI and not with the original sensors. The original sensors should not be replaced. If a sensor in a certain location has caused several events, yet the sensor trains and seems to operate normally, moving that particular wheel to a different location on the vehicle is a good way to isolate the concern to a certain sensor/wheel location. Rotate the wheels and road test the vehicle. This can be done in an attempt to replicate the concern and help determine if the concern followed the sensor or remained in the original sensor location.

If the vehicle has been stationary for more than 30 minutes, the sensors go into a "sleep mode" to conserve battery power and need to be "woken up" so they transmit the latest tire pressure information to the RTM. Refer to: Tire Pressure Monitoring System (TPMS) Sensor Activation (204-04B Tire Pressure Monitoring System (TPMS), General Procedures).

Training Sensors in a Different Order

If the first sensor fails the TPMS training procedure, the BCM aborts the entire procedure. Starting the training procedure at a different wheel is a technique which can be used to determine if the remaining sensors can train to the module. This can help save time determining if one sensor is damaged, other sensors are having concerns or the BCM is experiencing training difficulties with a certain TPMS sensor location.

TPMS Warning Indicator

The TPMS warning indicator is used to indicate both a low tire pressure event and a possible system fault condition. The message center displays additional information associated with the low tire pressure event or the system fault condition. Occasionally, the warning indicator and message center indicate faults that cannot be resolved by the customer. Treat these as TPMS faults that must be serviced.

TPMS Warning Indicator Illuminates Continuously

The TPMS warning indicator remains on continuously and the message center displays LOW TIRE PRESSURE when any of the tire pressures fall below the low pressure limit. When this condition exists, adjust the tire pressure to the recommended cold tire pressure indicated on the VC label.

Tire Pressure Monitoring System (TPMS) Warning Indicator Flashes

The TPMS warning indicator flashes for 70 seconds and then remains on continuously when the ignition is set to ON and the TPMS is malfunctioning. The TPMS status (TPMS_STATUS) PID can be used to determine why the TPMS warning indicator is flashing.

Tire Pressure Sensor Fault — The message center displays TIRE PRESSURE SENSOR FAULT when a TPMS sensor is malfunctioning. No communication with the BCM — The TPMS warning indicator illuminates when the IPC has not received any signals from the BCM for more than 5 seconds. The message center displays TIRE PRESSURE MONITOR FAULT. Tire Pressure Monitor Fault — The message center displays TIRE PRESSURE MONITOR FAULT when the TPMS is malfunctioning.

TPMS PID Definitions