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 PIDs can be combined with specific 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 contains PIDs used to keep track of the number of TPMS messages received from the 4 trained TPMS sensors. These PIDs can provide insight on the performance of the TPMS, and help establish the presence of an RFI source.

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

To determine if a RFI issue has been affecting the TPMS, perform the following:

1. Collect the last 5 TPMS events and determine if they were due to system faults or low tire pressure.
2. Collect the TPMS Hit Rate PID counters and compare them to the last 5 TPMS events.
3. 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 the last 5 TPMS events and BCMDTC 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 BCM.
4. An intermittent RFI source can also be the case when all 4 TPMS sensors show up in the last 5 fault events and BCMDTC B1182:00 (Tire Pressure Monitoring System (TPMS): No Sub Type Information) is present. The possible cause would a strong source of RFI noise.