Tire Pressure Low and Critical Tire Pressure

When the TPM module senses that pressure is below one of two calibrated thresholds, Tire Pressure Low or Critical Tire Pressure, the TPM module will indirectly operate the "Lo Tire" LCD message through the BCM and the warning alert through the Instrument Cluster to the BCM.

If the tire pressure is low (20 to 14 psi), the Low Tire Pressure Signal circuit will be pulsed to ground by the TPM module for two seconds on and then two seconds off. The BCM will send the "Lo Tire" LCD message and the Instrument Cluster will send a single warning alert request to the BCM. The BCM will also set a Tire Pressure Low DTC.

If the tire pressure is critical (14 to 0 psi), the Low Tire Pressure Signal circuit will be pulsed to ground by the TPM module for one second on then one second off. The BCM will then enable the "Lo Tire" LCD message and the Instrument Cluster will send the PCI Bus message to the BCM to sound the warning alert at the rate of one second off and one second on. The BCM will also set a Critical Tire Pressure DTC.

The module will continue to pulse to ground the Low Tire Pressure Signal circuit until the ignition is turned off, or the tire pressure transmitter(s) transmits a pressure above the calibrated threshold.

NOTE: A low tire pressure condition does not set a DTC in the TPM module. The DRBIII® can be used to view the last 32 transmissions in the module's memory and to confirm which tire was reporting the low-pressure condition.

If more than one condition is set at the same time, the TPM module will prioritize when the "Lo Tire" LCD message will be enabled. The priority rankings are listed below:

Critical Tire Pressure: "Lo Tire" LCD message flashes at one second on and one second off.

Tire Pressure Low: "Lo Tire" LCD message flashes at two seconds on and two seconds off.

TPM Module Initialized and TPM Diagnostic: "Lo Tire" LCD message on.

Less than four ID's learned "Lo Tire" LCD message on.

Transmitter Failure: "Lo Tire" LCD message on.

Normal tire pressure: "Lo Tire" LCD message not on.

No faults: "Lo Tire" LCD message not on.