Certified Service Advanced Diagnostics
Certified Service Expert Diagnosis
GM Original Equipment
GM Parts and ACDelco Parts Warranty

Car trouble symptoms can indicate minor or major car problems with your vehicle. Monitoring your vehicle’s key operating systems and components is critical for your vehicle’s health over the long term. That’s when our Certified Service technicians provide technical data for your GM vehicle with precision tuning.

This glossary of terms should help you identify your Chevrolet, Buick, GMC, and Cadillac vehicle's symptoms and assist you when discussing your concerns with your Certified Service technician. Check in at your local GM dealership to help conquer complex repair situations, putting data directly from your vehicle right at technicians’ fingertips. See below for more information about GM Factory Diagnostics.



Brake fade

Stopping distance seems to increase, causing longer braking distance, similar to braking at high speeds.

Low brake pedal

Brake pedal must be pushed unusually far to engage brakes.

Brake pedal pulsation

Brake pedal fluctuates while brakes are applied.


Vehicle has a tendency to move right or left when brakes are applied; brakes engage suddenly when applying steady pressure to brake pedal.


Cuts out

Temporary complete loss of power. Engine quits at irregular intervals. May occur repeatedly or intermittently, usually under heavy acceleration.


Mild to severe pings, usually worse under acceleration. Sounds like popcorn popping.


Engine runs after ignition switch is turned off. Runs unevenly and may make knocking noises.


Momentary lack of response as accelerator is pressed. Can occur at any speed. Usually most severe when starting from complete stop. May cause engine to stall.


Pulsation or jerking that changes with engine speed. Exhaust has a steady spitting sound at idle or low speed. Not normally felt above 30 mph.

Rough idle

Engine runs unevenly at idle. Car may also shake.


Engine delivers limited power under load or at high speed. Won't accelerate as fast as normal. Loses speed going up hills. Vehicle has less speed than normal.


Little or no increase in speed when accelerator is pushed down. Continuing to push pedal down will eventually give an increase in speed.


Engine stops running or dies out. May occur at idle or while driving.


Vehicle speeds up and slows down with no change on accelerator pedal. Can occur at any speed.



Suspension moves to extreme end of travel and hits compression bumpers. Feels like a heavy thud.

Excessive play

Steering wheel must be turned unusually far before vehicle responds.

Hard steering

Vehicle difficult to steer, especially during parking situations or when first started.


Vehicle moves to one side when steering wheel is released.


Rapid side-to-side motion of both front wheels felt in steering wheel.


Mushy or spongy ride; vehicle takes a long time to recover from bumps in the road.


Vehicle shakes.


Vehicle meanders, requiring frequent steering adjustments to maintain direction.


Antifreeze or coolant leak

Sweet odor, usually accompanied by steam from under the hood.

Axle leaks

Black stains with heavy, thick consistency.

Burning oil

Thick, heavy odor, sometimes accompanied by smoke from under the hood or from the exhaust.

Coolant streaks

Yellow, green, pink, or orange stains that are lighter and thinner than oil.

Crankcase, oil, power-steering
 fluid leaks

Brownish stains.

Electric short

Acrid odor, like burned toast.


Continuous, heavy sulfur odor, like rotten eggs.

Overheated brakes or clutch

Burning rubber odor.


Hot, metallic odor usually accompanied by antifreeze/coolant odor.

Transmission oil leaks

Reddish stains.

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