Tire Pressure Monitor Module: Notes

The TPM module is a microprocessor controller that monitors the transmissions from the transmitters at all times with the ignition on. The TPM module will store the last 32 transmissions from the tire pressure sensor/transmitters however, they cannot be observed as they occur using the DRBIII®. There are three important values included in these transmissions. They are listed as: why the transmission was sent, from which sensor it came from (LF, RF, RR, LR), and the tire pressure. There are four reasons why the tire pressure sensor/transmitter will send information to the TPM module:

TIRE PRESSURE SENSOR/TRANSMITTER INFORMATION SENDING REASONS

Supervisory	This is the normal mode, the transmitter will start to transmit information to the TPM module at 33 km/h (20 mph) and continue at a rate of one transmission per minute.
Pressure	If the pressure reading changes more than 10.34 kpa (1.5 psi) between the normal sampling period of 30 seconds, the transmitter will send this change information to the TPM module within 30 seconds.
Wake	This is the very first message that the tire pressure sensor/transmitter sends to the TPM module. This wake mode will only occur after the vehicle has reached 33 km/h (20 mph).
Magnet	When a magnet is placed on the transmitter it closes a reed switch inside the transmitter and enables the transmitter to send a RF signal to the TPM module. Placing a magnet on the transmitter would normally be done for programming purposes when the TPM module or the tire pressure sensor/transmitter is being replaced.

The TPM module compares the transmitted tire pressure to the two pressure thresholds, low and critical. If the module determines that the tire pressure transmitted is below the low or critical pressure, the module will request the "Lo Tire" LCD message to come on.

The TPM module performs diagnostic routines; store Diagnostic Trouble Code(s) (DTC), and provides the system status to the Body Control Module (BCM.) When the TPM module determines there is a fault present, the Low Tire Pressure Signal circuit will be pulled low (grounded.) The BCM intern sends a PCI Bus message to the Instrument Cluster to enable the "Lo Tire" LCD message. The cluster will then send the appropriate chime message to the BCM to sound a warning alert.

The TPM module retains its own ID number, each of the four transmitter ID numbers, module version, date of manufacture, and low/critical thresholds.

NOTE: Tire pressure sensor/transmitter replacement involves removal of the tire from the wheel. Service procedures can be found in the wheel. Service procedures can be found in SENSOR - TPM .