Understanding the difference between tire pressure monitoring systems (TPMS) and automatic tire inflation systems (ATIS), as well as proper maintenance for both systems, is an important part of supporting a well-run fleet.
“The function of TPMS is to alert drivers when a tire is low, but the system does not add air to the low tire. ATIS not only lets the driver know that a tire is low, but also adds air to the underinflated tire as the vehicle is running down the highway,” says Al Cohn, director of new market development and engineering support for Pressure Systems International.
“TPMS is a warning system that provides alerts when there is a problem. If maintenance is inspecting the vehicle and the OEM dash or the Bendix SmarTire display does not have an active warning or fault, then no action needs to be taken. If, however, there is an active alert or fault indicated by the system, action to correct the issue is required. Pressure or temperature warnings should be addressed accordingly,” adds Jon Intagliata, product manager of TPMS for Bendix Commercial Vehicle Systems.
In addition to tire pressure and temperature warnings, there are a couple of system warnings that should be addressed by maintenance: low battery alerts and sensor faults. Prior to a sensor battery failing, a low battery alert is issued indicating the sensor will need to be replaced in the near future. Sensor faults are typically the result of a missing or damaged sensor that has stopped communicating with the ECU. Sensor faults should be corrected quickly, as the tire position that is faulted is not being monitored by the TPMS system.
Both TPMS and ATIS are low maintenance systems, notes Cohn. “TPMS requires a battery on each of the tire/wheel sensors. It is necessary to confirm that the signal from each tire sensor is being sent to the hand-held reader or to the reader in the tractor. ATIS requires that the shop confirm that the warning light on the front of the trailer is working properly. Also during normal PMs make sure to check for any system leaks (rotary union or hoses) using soapy water,” he explains.
In ATIS, the rotary union is the only wearable component that will need to be replaced. Soapy water will identify a rotary union that is worn out. They typically last three to seven years, or more. Check hoses for damage and leaks. With TPMS, confirm that the sensors are working properly.
“Shop staff should be educating drivers about how to use the system while they are on the road,” says Chris Steph, ITMS product manager for Stemco LP. “Features like visual low tire alerts (at the wheel end); in-cab alerts and the low-tire-logging feature are critical to understanding when action should be taken. Further, drivers should be trained on the specific actions they need to take for low tire alerts. Each fleet will tend to have slightly different policies or procedures, so this really becomes fleet specific for their in-house procedures.”
Steph suggests monitoring the following key elements:
- Inspect hoses and valve stems for wear or abrasions
- Inspect sensors for damage
- If the maintenance tech has a HandBAT RF reader, sensors may be read and information inspected for diagnostic purposes
- Inspect brackets/mounting hardware for excessive corrosion