A warning light comes on, so someone connects a scanner and reads a code. That sounds like a diagnosis. In practice, it is usually the beginning of one.
A diagnostic trouble code tells a technician what the vehicle’s computers have detected. It does not necessarily identify the failed part, and it certainly does not mean that the part named in an online search should be replaced. The same code can have several possible causes. Wiring, a loose connection, low voltage, a mechanical problem or another control module may all produce similar symptoms.
This is where the technician’s training—and the information available to that technician—makes a difference.
Modern vehicles do much more than turn on a check-engine light
Today’s vehicles contain computers that manage the engine, transmission, brakes, climate control, steering, safety equipment and many convenience features. These modules exchange information over communication networks running throughout the vehicle.
That arrangement makes vehicles more capable, but it can also make problems less obvious. A weak battery may create warnings in systems that appear unrelated to the battery. A damaged wire can interrupt communication between modules. A software issue may produce a symptom without leaving behind a visibly broken component.
The dashboard message is what the driver sees. Finding the condition that caused it requires a methodical diagnostic process.
What GM dealership diagnostic resources include
As a GM dealership service department, Curry Auto Center has access to manufacturer resources developed for Chevrolet, Buick, GMC and Cadillac vehicles. Those resources include GM diagnostic software, current service information, technical publications, manufacturer repair procedures and special service tools designed for GM vehicles.
That is more than a larger list of trouble-code definitions. Factory information can help a trained technician determine:
-
How a particular system is designed to operate
-
Which conditions must be present before a code is set
-
What tests should be completed and in what order
-
Whether GM has published updated information about a known condition
-
Whether a module requires programming or a software update
-
Which specifications and repair procedures apply to the exact vehicle
The vehicle’s model, model year, engine, drivetrain and installed equipment can all affect the correct procedure. Information written for a similar-looking vehicle is not always information written for yours.
Why reading the code is not the same as diagnosing the vehicle
Consider a code indicating that a sensor reading is outside its expected range. The sensor might have failed. It might also be reporting a real problem somewhere else in the system. Replacing it without testing can leave the original problem untouched.
A trained technician may need to examine live vehicle data, compare several readings, inspect wiring, test voltage or pressure, reproduce the condition and consult the applicable diagnostic procedure. Sometimes the most important result of a test is ruling out the part that initially seemed suspicious.
This is one reason Curry Auto Center continues to invest in technician education. Our mechanical technicians hold 43 ASE certifications and 43 General Motors factory certifications. The GM credentials include training in engine performance, diesel engine performance, engine repair, electrical systems, transmissions, brakes, steering and suspension, heating and air conditioning, and electric and hybrid vehicles.
Electrical and engine-performance training is especially relevant to modern diagnosis, but complicated concerns rarely remain confined to one neat category. A drivability complaint can involve the engine, transmission, fuel system, electrical system or communication among several modules. Broad training gives the technician a better foundation for following the evidence instead of guessing.
Some warning lights require immediate attention
Not every dashboard light means the same thing. A maintenance reminder is different from an oil-pressure warning, an overheating warning or a flashing check-engine light.
If a red warning appears, the engine is overheating, the oil-pressure light comes on or the check-engine light is flashing, continuing to drive may cause damage or create a safety concern. Move to a safe location and consult the owner’s manual for the appropriate action. If the vehicle is running poorly, making an unusual noise or showing several warnings at once, it is sensible to stop and ask for professional guidance.
For a steady amber check-engine light with no obvious change in operation, the vehicle may still be drivable, but the condition should not simply be ignored. A service advisor can help determine how promptly it should be inspected based on the light, the symptoms and the vehicle involved.
Factory information is useful on older GM vehicles, too
Dealership diagnostic resources are not valuable only while a vehicle is new or covered by warranty. Chevrolet, Buick, GMC and Cadillac vehicles that have been on the road for many years still benefit from technicians who understand GM systems and can consult manufacturer information.
Older vehicles may present intermittent problems, previous repairs, worn wiring or several issues at the same time. A disciplined diagnostic approach becomes more important—not less—when the answer is not immediately apparent.
Curry Auto Center also works on many non-GM vehicles. Our ASE-certified technicians apply the same basic principles to every diagnosis: verify the concern, gather information, test the system and identify the cause before recommending a repair.
Diagnosis before replacement
Customers understandably want to know what a repair will cost. Before that question can be answered accurately, someone must determine what actually needs to be repaired.
A scan tool is an important part of that process, but it does not replace the technician using it. The value comes from combining vehicle data, correct service information, appropriate testing and the judgment developed through training and experience.
Drivers can review Curry Auto Center’s 2026 Technician Certification Report, learn about our GM factory-trained technicians or schedule a service appointment at our Bloomington service department.