Low Tire Pressure Indicator: Service and Repair
Tire Pressure Sensor Learn
Special Tools
J-46079 Tire Pressure Monitor Diagnostic Tool
TPM Learn Mode Description
The tire pressure monitor (TPM) system uses the liftgate module (LGM), body control module (BCM), exterior lamp switch, 4 RF transmitting pressure sensors, and the serial data circuit to perform the TPM learn mode functions. The sensor learn procedure must be performed after every tire rotation, LGM replacement, or sensor replacement. Once the TPM learn mode has been enabled, each of the sensor's unique identification (ID) codes can be learned in to the LGM memory. When a sensor's ID has been learned, the LGM sends a serial data message to the BCM to sound a horn chirp. This verifies the sensor has transmitted its ID and the LGM has received and learned it. The LGM must learn the sensor IDs in the proper order to determine correct sensor location. The first learned ID is assigned to the left front location, the second to right front, the third to right rear, and the fourth to left rear.
Sensor Functions Using J-46079
Each sensor has an internal low frequency (LF) coil. When the J-46079 is used in activate mode it produces an LF transmission that activates the sensor. The sensor responds to a LF activation by transmitting in learn mode. When the LGM receives a learn mode transmission while in TPM learn mode, it will assign that sensor's ID to the location on the vehicle relative to the order in which it was learned.
Sensor Functions Using Pressure Increase/Decrease Method
Each sensor takes a pressure measurement sample once every 30 seconds while in stationary mode. If the tire pressure increases, or decreases by more than 8.3 kPa (1.2 psi) from the last transmitted pressure, another measurement will occur immediately to verify the change in pressure. If a pressure change has indeed occurred, the sensor transmits in re-measure mode. When the LGM receives a re-measure mode transmission while in TPM learn mode, it will assign that sensor's ID to the location on the vehicle relative to the order in which it was learned.
Learn Mode Cancellation
The learn mode will cancel if the ignition is cycled to OFF or if more than 2 minutes has elapsed for any sensor that has not been learned. If the learn mode is cancelled before the first sensor is learned, the original sensor IDs will be maintained. If the learn mode is canceled for any reason after the first sensor is learned, all IDs are erased from the LGM memory and if equipped, the DIC will display dashes for tire pressures.
TPM Learn Procedure
Important: Stray signals from other TPM equipped vehicles just driving by can be inadvertently learned. If any random horn chirps are heard from the vehicle while performing the learn procedure, most likely a stray sensor has been learned and the procedure will need to be cancelled and repeated. Under these circumstances, performing the TPM Learn Procedure away from other vehicles would be highly recommended. In the event a particular sensor activation does not cause the horn to chirp, it may be necessary to rotate the wheel valve stem to a different position due to the sensor signal is being blocked by another component.
Before proceeding with the steps below, verify the following:
* No other sensor learn procedure is being performed simultaneously within close proximity.
* Tire pressures are not being adjusted on another TPM equipped vehicle within close proximity.
* Park Brake and Headlamp Switch input parameters are functioning correctly.
1. Turn ON the ignition, with the engine OFF.
2. Apply the parking brake.
3. Cycle the exterior lamp switch from OFF to parking lamps 4 times within 4 seconds. A double horn chirp will sound and the low tire pressure indicator will begin to flash indicating the learn mode has been enabled.
4. Starting with the left front tire, learn the tire pressure using one of the following methods:
* Hold the antenna of the J-46079 against the tire sidewall close to the wheel rim at the valve stem location then press and release the activate button and wait for a horn chirp.
Caution: Over inflating tires may cause personal injury or damage to the tires and wheels. When increasing tire pressure do not exceed the maximum inflation pressure as noted on the tire sidewall.
* Increase/decrease the tire pressure for 8-10 seconds then wait for a horn chirp. The horn chirp may occur before or up to 30 seconds after the 8-10 second pressure increase/decrease time period has been reached.
5. After the horn chirp has sounded, repeat step 4 for the remaining 3 sensors in the following order:
* Right front
* Right rear
* Left rear
6. After the LR sensor has been learned, a horn chirp will sound indicating all sensors have been learned.
7. Turn OFF the ignition to exit the learn mode.
8. After the learn mode has been exited, adjust all tires to the recommended pressures. Refer to Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label (Vehicle Certification, Tire Placard, Anti-Theft, and Service Parts ID Label).