TPMS PID Definitions

WARNING: This page is about a different car, the 2015 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

The BCM monitors the TPMS status. Use the diagnostic scan tool to view the current status of the TPMS status (TPMS_STATUS) PID. This helps identify the current system status and may aid in diagnosing the system. The PID has 4 valid states:

TPMS_STATUS PID displays SENSOR FAULT if the BCM has not received the tire pressure data from 1 to 3 TPMS sensors for 20 minutes when vehicle speed is above 32.2 km/h (20 mph).
TPMS_STATUS PID displays SYSTEM FAULT if the BCM has not received the tire pressure data from all 4 TPMS sensors for 20 minutes when vehicle speed is above 32.2 km/h (20 mph).
TPMS_STATUS PID displays LOW if the BCM has detected that at least 1 TPMS sensor is reporting low tire pressure.
TPMS_STATUS PID displays SYSTEM ACTIVE if the TPMS is functioning normally.

Last Warning Event PID Definitions

The TPMS uses the TPMS last warning event Parameter Identifications (PIDs) to store detailed information about the last 5 times the TPMS warning indicator was activated. These Parameter Identifications (PIDs) can be used to acquire more information about a particular TPMS event, but must be used carefully.

PID	Definition
EVT1_AGE_IGN through EVT5_AGE_IGN	The number of key cycles since the TPMS was activated. This PID cycles from zero to 255 and then starts over from zero again. This can be used to determine how long ago a TPMS event occurred and the time (in key cycles) between events.
EVT1_TR_LOC through EVT5_TR_LOC	This is the last programmed location for the TPMS sensor identifier causing each TPMS event. Due to tire rotation, the sensor may no longer be at the original location. It is suggested that all the Parameter Identifications (PIDs) be recorded, the system retrained, and then the sensor identifier Parameter Identifications (PIDs) be used to pinpoint the actual location of each sensor.
EVT1_PRES_BP through EVT5_PRES_BP	This is the tire pressure associated with each TPMS indicator event. This can be used along with the function code to clearly identify the TPMS events that were strictly due to low pressure. It can also be used to determine when a sensor is transmitting inaccurate tire pressure.
EVT1_SNSR_ST through EVT5_SNSR_ST	Describes the warning status of each TPMS event by using the information received from the TPMS_STATUS PID. If there is a communication concern, the status could be NORMAL. UNKNOWN NORMAL (normal operation) LOW (low pressure event) FAULT (sensor fault or system fault)
EVT1_SNSR_ID through EVT5_SNSR_ID	This is the identifier of the sensor involved in each TPMS event. EVT1 is the most recent event that triggered the TPMS warning indicator.

Radio Frequency Interference (RFI)

RFI can be caused by:

Video equipment has been found to cause RFI especially when the video and power supply lines are near the TPMS.
Anti-theft alarms (even those installed by the dealership) have been found to create enough RFI to cause the TPMS to malfunction or lose considerable range. These anti-theft alarms can be difficult to locate, as they are usually hidden somewhere out of the way for reduced accessibility.
Many in-vehicle cell phone chargers have been found to cause considerable RFI. The vehicles with the power point closest to the RTM are the most affected. It must be noted that most cell phone chargers do not produce high levels of RFI all the time. This depends on the state of charge of the cell phone battery. The phone battery must be almost completely discharged in some cases.
Power supplies and DC/ AC inverters typically create a lot of RFI. Most consumer grade equipment has very little filtering or shielding.

Using Hit Rate Parameter Identifiers (PIDs) to Determine the Presence of RFI

If an intermittent RFI issue is suspected, the information contained in the last 5 TPMS warning event Parameter Identifiers (PIDs) can be combined with specific Parameter Identifiers (PIDs) from the BCM to determine which TPMS sensors are being affected and if a RFI source is currently present in the vehicle.

The BCM module contains Parameter Identifiers (PIDs) that keep track of the number of TPMS messages received from the 4 trained TPMS sensors. These Parameter Identifiers (PIDs) can provide insight on the performance of the TPMS, and can help establish the presence of an Frequency Interference (RFI) source.

TPM_HITS_LF (Tire Pressure Monitor Hit Rate Left Front) - The number of TPMS messages received by the BCM module from the LH front sensor
TPM_HITS_RF (Tire Pressure Monitor Hit Rate Right Front) - The number of TPMS messages received by the BCM module from the RH front sensor.
TPM_HITS_LRO (Tire Pressure Monitor Hit Rate Left Rear Outer) - The number of TPMS messages received by the BCM module from the LH rear sensor
TPM_HITS_RRO (Tire Pressure Monitor Hit Rate Right Rear Outer) - The number of TPMS messages received by the BCM module from the RH rear sensor.

Method for determining if a RFI issue has been affecting the TPMS:

Collect the last 5 TPMS events and determine if they were due to system faults or low tire air pressure.
Collect the TPMS Hit Rate PID counters and compare them to the last 5 TPMS events.
If the TPMS Hit Rate PID counters are significantly different from each other or if the locations with lower hit rate values show up as fault locations in last 5 TPMS events and BCM DTC B124D:02 (Tire Pressure Sensor: General Signal Failure) is present, an intermittent RFI source is most likely preventing the signals from these TPMS sensors from reaching the RTM.
An intermittent RFI source can also be the case when all 4 TPMS sensors show up in the last 5 fault events and BCM DTC B1182:00 (Tire Pressure Monitoring System (TPMS): No Sub Type Information) is present. The possible cause would a strong source of RFI noise.

Original Equipment Manufacturer (OEM) Modules

In some cases the RFI may actually be caused by a module or ground on the vehicle. Depending on the severity of the concern, a dirty ground, improperly built ground shield or module can disable the system. Modules which have microcontrollers using clock circuits to create timing pulses for the microprocessor may radiate RFI.

Using Customer Electronics to Pinpoint Radio Frequency Interference (RFI)

This method can be a way to determine the cause of a concern before the sensors and module are replaced with little or no effect on system performance. Discuss with the customer what types of devices were being used when the event occurred. Determine which power points were being used and, if necessary, ask the devices be activated to determine their affect on the TPMS.

Options for Eliminating Intermittent TPMS Operation Caused by