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Air pressure will not build

Updated: 2026-11-10

Slow build-up or falling pressure points to a leak, the compressor, or the air dryer. Without full pressure the brakes will not release fully, and on a long downgrade there may not be enough braking at all. This is one case where you do not head out.

How to approach it

An engine that does not build boost has a problem in the intake or the turbo: the turbocharger, intercooler, air filter or hoses. First inspect the air filter and the boost hoses for cracks and leaks, then check the boost pressure sensor. If there are intake and pressure codes, do not work the engine hard until the leak is found. A sudden loss of power is usually accompanied by a torque limit.

Stop if the reading shows any of these codes: SPN 117, SPN 118, SPN 1087, SPN 1351, SPN 82.

These codes usually come with it: SPN 1048.

Codes that mean stop now

Other codes for this system

What happens if you keep driving

Time you have: Minutes

Part of the brake circuit or ABS/EBS is out of service. The pedal may still feel normal — until the first emergency stop or descent.

Next comes longer stopping distance, a skid on a slick surface, failure on a long downgrade. This is the case where "I will take it slow" does not work.

What to check on the spot

Let the air system build to working pressure and listen for leaks. Don’t drive with faulty brakes.

Can I keep driving

The answer depends on the code, not the light. A yellow light is a warning; a red one means do not move. But even under a yellow light there are faults that require stopping right away — low oil pressure, overheating, lost brake pressure. Enter the code — the reference will tell you plainly whether to keep driving or stop.

Know the code number? Type it into the search — or paste the whole list from the scanner and we will show which fault is the real one.