Tire Pressure Monitoring System - Low-Pressure Situation

Since September 2007, federal law has required that every new domestic passenger vehicle with a gross vehicle weight rating (GVWR) of 10,000 pounds be factory-equipped with a tire-pressure-monitoring system (TPMS). The legislation requires that the system indicate when one or more tires has deflated beyond a preset threshold, usually 25 percent below the manufacturer-recommended pressure.

This mandate grew out of the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act, which passed in November 2000. TREAD was the result of congressional hearings prompted by a spate of rollover accidents involving Ford Explorers equipped with certain Firestone tires.

There are two types of TPMS: direct and indirect. Indirect systems use the vehicle's wheel sensors to compare the turning circumference of each tire with that of the other three. These systems aren't very accurate and will not issue a warning if all four tires lose air equally, as might happen when outside temperatures drop. For these reasons, indirect systems have mostly fallen out of use.

Direct systems, such as the ones used in Corvettes, use sensors fitted inside the tire's air chamber, where they read pressure directly. The C4 system uses a transmitting wheel sensor held in place by large band clamp. Each sensor has a separate identification color and frequency, which is transmitted as the wheel turns. The movement of the wheel provides the energy necessary to power the transmitter. If the tire pressure drops below 25 psi, the sensor stops transmitting to the receiver, and the "Service LTPWS" lamp illuminates. The sensors don't require batteries, and the receivers don't need to be reprogrammed.

The C5 and C6 systems use a transmitting wheel sensor attached to the tire's valve stem. A separate sensor/transmitter in each wheel shares its receiver with the keyless entry system. The receiver is programmed at the factory to recognize which sensor is at each wheel location. If the tires are rotated, a sensor is replaced, or the system simply loses its calibration, a warning light will illuminate in the instrument panel. At this point, the receiver must be reprogrammed.

Fortunately, reprogramming the receiver on a C5 or C6 is a simple task you can perform anywhere, whether at home or at the track. The C5 system can be reprogrammed using either a strong magnet or a wheel-sensor-reprogramming tool; the C6 system requires the latter method.

Follow along now as we cover the reprogramming procedure for both cars.

Special thanks to Gerhard Bunge at Eckler's Corvette Parts.

If you rotate your tires or replace a wheel sensor, your tire-pressure-monitoring sensors will need to be reprogrammed. The following is a step-by-step procedure for reprogramming the C5 sensors:

1. Let the vehicle sit for two minutes; then turn the ignition on.

2. Press the "Reset" button to clear any Instrument Panel Cluster (IPC) warning messages.

3. Press and release the "Options" button on the Driver's Information Center (DIC) and scroll through the display options until the IPC display is blank.

4. Press and hold the DIC "Reset" button for 3 seconds.

5. Press the "Options" button again until the "Tire Training" message appears.

6. Press the "Reset" button until the "Learn Left Front Tire" message appears on the IPC.

7. Place a large magnet over the left front valve stem. The horn will sound, indicating the left front TPMS sensor is programmed. If this takes more than 15 seconds, pull the magnet back and try again. If the procedure fails after three tries, you'll need to start the sequence over from the beginning. GM sells a special U-shaped magnet specifically for this job (PN J41760), but a large speaker magnet will usually work just as well.