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Discussion Starter · #1 · (Edited)
While the news in this article by GM TechLink is, in one sense, really old news, at our Corvette club meeting last week, a week in which temperatures dropped 20 degrees, three people spoke up about their DIC's telling them low air pressure (meaning that at least one of their tires was down a full five PSI from spec).

These are all Corvette lovers, and this is a subject we discuss each fall and each Spring, that a ten degree change in temperature corresponds, roughly, to a one PSI difference in tire pressure. A study by the US Dept. Of Energy showed that at any one time, approximately, 35% of all vehicles have at least one tire with at least five pounds lower air pressure than recommended. And, as we all know, lower air temperature than desired is costly in terms of both fuel economy and prematurely wearing out our tires. With our Corvettes all we have to do is to press a button, and we know what the tire pressure is in each tire.

Sorry about my "soap box." I am off it now, and here's that info and more from GM's TechLink on its application to our vehicles.

GMTechLink said:
As the temperature drops in the winter months, more customers will see the low tire light on their instrument cluster illuminate indicating low tire pressure.

As a rule of thumb, tire pressure will change about 7 kPa (1 psi) for every 10°F (6°C) decrease or increase in temperature; so tire pressure will drop when it gets colder outside and rise when it gets warmer.

If the low tire pressure light illuminates, customers that are not familiar with the operation of the Tire Pressure Monitor system in their vehicle may come to the dealership for service.

TPM Low Tire Light

If the TPM low tire light on the instrument panel is illuminated, determine if the light is due to low tire pressure or if it is the result of a TPM malfunction.

Turn the key on, without starting the engine:

• If the low tire light illuminates and stays on solid (a low tire pressure message may be displayed on the Driver Information Center), tire air pressure is low. Properly adjust all tire air pressures to the recommended levels. Driving the vehicle will turn off the light.

• If the low tire light illuminates for a few minutes when the vehicle is started and then goes off after driving, the tire air pressure is likely low in one or more of the tires. After driving awhile, the tires will heat up, allowing air pressure to increase above the threshold, causing the light to go off. Properly adjust all tire pressures to the recommended levels.

• If the low tire light flashes for one minute and then stays on solid (a service tire monitor system message may be displayed on the Driver Information Center), a TPM system condition exists. The vehicle will require further diagnosis.

Dashes Indicate System Malfunction

If dashes (—) are displayed in only one or two of the tire pressure readouts, it is likely caused by a previous TPM system relearn that was performed incorrectly due to interference from another vehicle’s TPM system during the relearn process. Each tire monitor sensor is learned to a specific vehicle corner. When performing a TPM relearn (only after a tire rotation or replacement of a TPM sensor or module), use a scan tool (GDS 2 or the Tech 2), the J-46079 TPM Tester (Fig. 10) or the EL-50448 TPM Activation Tool (Fig. 11) to initiate the relearn process and lock out other vehicle TPM signals that may be broadcasting in the area. This method avoids storing false TPM I.D.s and will prevent vehicles from returning with dashes displayed in the tire pressure readouts and/or a flashing low tire light. Check the four TPM I.D.s with a scan tool prior to and following the relearn procedure to verify they are the same.

If dashes (—) are displayed in all four of the tire pressure readouts, there is a system condition. Follow the appropriate Service Information procedures.

- Thanks to Dave MacGillis.
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