Chevrolet T Series Warning Lights: What They Mean

Red: stop or act now

Hydraulic Brake System Warning Light

Master cylinder fluid is low or the hydraulic brakes have a problem; a warning tone also sounds.
What to do: Pull off the road and stop carefully. If the light stays on, have the vehicle towed for service. PDF page 104

Other warnings and indicators

Air Brake System Warning Light

Brake reservoir pressure has dropped below 60 psi. The parking brake may apply suddenly if pressure falls to 35-45 psi.
What to do: Drive only to the nearest safe point and stop the vehicle. Stop as soon as you can. PDF page 105

Service Transmission Warning Light

On Allison automatic transmissions, a transmission malfunction. The transmission may be stuck in one gear and unable to go fast or reverse.
What to do: Do not shift. Drive directly to an authorized dealer for service, or have the vehicle towed. PDF page 103

Service Brakes Soon Warning Light

There may be something wrong in the brake system; a warning tone also sounds.
What to do: Have the system repaired immediately. If it stays on, have the brake system inspected right away. PDF page 104

Low Coolant Warning Light

The system is low on coolant and the engine may overheat. It may also come on if automatic engine shutdown has begun.
What to do: Have the vehicle serviced as soon as you can. PDF page 108

Water-in-Fuel Indicator Light

Water has collected in the fuel filter, which can damage the fuel injection system and engine.
What to do: Drain the fuel filter. If it comes on right after refueling, turn off the engine and have the water drained at once. PDF page 160

Parking Brake Warning Light

Comes on when the parking brake is set. It stays on if the parking brake does not release fully. PDF page 105

Range Inhibit Warning Indicator

On Allison transmissions, a flashing bar, light, or gear display means transmission range shifts may not occur.
What to do: See the Allison Automatic Transmission Operator's Manual for shift inhibit limitations. PDF page 103

Wait to Start Light

The glow plugs are on while the ignition key is in ON/RUN or START.
What to do: Wait until the indicator turns off before turning the key to START. Below 0°C, wait no more than 10 seconds. PDF page 108

Summarized in our own words from the 2010 Chevrolet T Series owner's manual (AI-assisted; every light name was matched against its cited page 2026-10-18). Your vehicle may not have every light, and other years can differ. A red warning that stays on usually means stop safely and check: your manual has the final word.