Tire Pressure Monitoring System Description, Operation and Diagnostics

The purpose of this bulletin is to further explain information found in SI and the Owner's Manual about the function of the Tire Pressure Monitoring (TPM) System.

The Tire Pressure Monitor (TPM) system warns the driver when a significant loss of tire pressure occurs in any of the four tires while the vehicle is being driven.

The system uses the passenger door module (PDM), Body Control Module (BCM), driver information center (DIC), instrument panel cluster (IPC), a radio frequency (RF) transmitting pressure sensor inside each wheel/tire assembly and the serial data circuit to perform the system functions. When the vehicle speed is less than 32 km/h (20 mph), the sensors go into stationary mode. In this mode, the sensors transmit once every 60 minutes to minimize sensor battery consumption. As the vehicle speed increases, centrifugal force closes the sensor's internal roll switch causing the sensors to go into drive mode. In this mode the sensor transmits once every 60 seconds. The PDM receives and translates the data contained in each sensor's RF transmission into sensor presence, sensor mode and tire pressure. If the TPM system detects a significant loss of tire pressure, or any of the tire pressures are 25% below the vehicle's recommended tire pressure, the CHECK TIRE PRESSURE warning message is displayed on the DIC and the low tire pressure warning indicator is displayed on the IPC, which appears as a cross section of a tire with an exclamation mark inside. Both the DIC message and the IPC indicator can be cleared by adjusting tire pressures to the recommended kPa/psi. The PDM has the ability to detect malfunctions within the TPM system. Any malfunction detected will cause the DIC to display the SERVICE TIRE MONITOR warning message.

Sensors

The sensor, with built-in valve stem, is inserted from the inside, through a hole in the wheel. The sensor is retained by a nut and is sealed by a grommet. The sensors are located within the drop well of the wheel. It is important to be careful when using a tire machine when mounting or dismounting a tire. The sensor could be damaged in two ways; either by direct contact with the machinery or by the bead of the tire as it is stretched over the wheel rim.

The sensor is powered by a 3 volt lithium battery with an expected life of 10 years, or 160,000 km (100,000 mi). When the battery in a sensor runs down, it is necessary to replace the sensor. Batteries are not serviceable.

Valve Stem

The valve stem cap is made of aluminum and the valve core is nickel-plated to resist corrosion. The end of the stem serves as the sensor's antenna.

Important :  DO NOT replace either the cap or the valve with standard parts. This will interfere with the sensor's ability to transmit.

Control Module Set-up

The service replacement PDM/Switch assembly comes with the TPM system disabled to allow the same part number PDM to be used in both TPM and non-TPM equipped vehicles. Verify that the vehicle is TPM equipped (RPO UJ6). After a PDM/Switch replacement, the TPM System Enable procedure (SI Document ID #1311194) must be performed for the Tire Pressure Monitor system to function properly.

Important: Once the TPM option is enabled in the PDM, it cannot be disabled.

After PDM/Switch assembly replacement, each of the tire pressure sensors unique identification codes must be learned into the PDM's memory.

Sensor Relearn

Once the learn mode has been enabled, each of the sensor's unique identification codes can be learned into the PDM's memory. Each sensor takes a pressure measurement sample once every 20 seconds while in stationary mode. If the tire pressure increases, or decreases by more than 11 kPa (1.6 psi) from the last pressure measurement, another measurement will occur immediately to verify the change in pressure. If a pressure change has indeed occurred, the sensor transmits a remeasure mode transmission. When the PDM receives a remeasure mode transmission while in sensor learn mode, it will assign that sensor ID to the location on the vehicle relative to the order in which it was learned. When a sensor's ID code has been learned, the PDM sends a serial data message to the BCM to sound a horn chirp. This verifies the sensor has transmitted its ID code and the PDM has received and learned it. The PDM must learn the sensor's ID codes in the proper sequence in order to determine sensor location. The first learned ID is assigned to the left front, the second to right front, the third to right rear and the fourth to left rear. The TPM system will cancel the learn mode if more than 2 minutes have passed and no sensors have been learned, or if the system has been in learn mode for more than 5 minutes. If the learn mode is cancelled before any sensor has been learned, the PDM will remember all current sensor IDs and their locations. As soon as the first sensor ID code is learned, all other IDs are erased from the PDM's memory. Refer to the Owner's Manual or SI Document ID #1311203 for the Tire Pressure Sensor Learn procedure.

J 46079 - Tire Pressure Monitor (TPM) System Diagnostic Tool

The J 46079 TPM diagnostic tool will test the TPM system and can also be used to activate the sensors after a tire rotation, so the receiver can learn the new sensor locations. In addition, J 46079 can be used for the Tire Pressure Sensor Test and Receiver Test.

Tire Pressure Sensor Learn Procedure

The sensor learn procedure must be performed after every tire rotation, sensor replacement, or receiver replacement.

1. Enable the tire pressure sensor learn mode in the receiver.
2. Starting with the left front tire, hold the antenna of the J 46079 against the tire sidewall close to the wheel rim at the valve stem location.
3. Press and release the "Activate" button. The main display will show moving waves during activation and then the sensor will transmit. The tool will display the sensor's transmission data and signal strength and a horn chirp will sound within 3-5 seconds.
4. After a horn chirp has sounded, proceed as in step 3 for the remaining 3 sensors in the following order:

•	Right Front

•	Right Rear

•

Left Rear

After all 4 sensors have been learned, exit the learn mode.

Tire Pressure Sensor Test

The sensor test procedure is used to verify that the sensors can transmit valid data after they have been activated with a Low Frequency (LF) transmission from the J 46079. During this procedure, the J 46079 will receive sensor transmissions and display the transmission data on the screen.

1. Hold the antenna of the J 46079 against the tire sidewall close to the wheel rim at the valve stem location.
2. Press and release the "Activate" button on the tool. The circling symbol indicates the tool is scanning for the sensor's transmission.
3. With the J 46079, observe the screen and wait 3-5 seconds for the sensor's transmission to be received. The screen should display an 8-digit ID number, tire pressure within 13 kPa (2 psi) of actual tire pressure, learn mode and good signal strength.
4. Proceed as in step 3, for the remaining sensors to verify all sensors are operating properly.

The Tire Pressure Sensor test cannot verify if the sensors internal roll switch is functioning. The vehicle must be test driven to determine if the internal roll switch is functioning. Refer to the electronic Service Information for further diagnostic information.

Receiver Test

The receiver test procedure is used to verify the receiver can receive and translate the data from simulated sensor transmissions.

1. Enable the learn mode in the receiver.
2. Locate the J 46079 in a central location in the passenger compartment of the vehicle.
3. Press and release the "Simulate" button.
4. Press and release the "Start" button and the J 46079 will begin to transmit a simulated sensor transmission. When the receiver receives the simulated sensor transmission, a horn chirp will sound, or the DIC will display the next sensor to be learned.
5. Press and release the "Next" button then the "Yes" button after a horn chirp has sounded or DIC message is displayed.
6. Repeat step 5 for the remaining 3 sensor locations until all 4 simulated sensor transmission have been learned into the receiver's memory. The J 46079 will display the preset ID numbers and tire pressures for each location.
7. With the scan tool, observe the TPM data list and verify the sensor IDs and tire pressures match what is displayed on the J 46079 screen and all 4 sensor modes are "Learn".

After-Market Wheels/Tires

Due to the wheel and tire profile of some after-market wheels and tires, the TPM sensor may not seat into the rim. It's important to be careful when using a tire mounting machine. The sensor could be damaged in two ways; either by direct contact with the machinery or by the bead of the tire as it is stretched over the wheel rim. If the vehicle is equipped with a TPM system, it cannot be disabled. Failure to install the TPM sensors will result in the system setting codes and a message appearing on the IP or DIC.

Tire Pressure Sensor Grommet Replacement

Any time a Tire Pressure Sensor is being reinstalled, it is important to replace the grommet on the sensor. The grommet is compressed during installation. Reuse of a grommet can cause an improper seal and result in an air leak. Refer to SI Document ID #131207 for the grommet replacement procedure.

Use of Tire Sealants

Tire sealants can be used on vehicles with tire pressure sensors. However, the sensor must be replaced after a sealant is used. The sealant can obstruct the small pressure sensing port on the front of the sensor body, causing the TPM system to display incorrect/false tire pressure readings.

Tire Rotations

Each TPM sensor has a unique identification code. Any time the vehicle's tires are rotated, the identification codes will need to be learned to the new tire/wheel location. If the learn procedure is not performed, the system will continue to report the correct pressures, but will assign them to the wrong locations on the vehicle. If a system malfunction has occurred and a DTC has set, it will also indicate the wrong sensor location in the DTC descriptor when performing system diagnosis. Follow the procedure as outlined in the Owner's Manual or SI Document ID #1311203.

Parts are currently available from GMSPO.