Diagnostics
Reading a fault code tells you where the car logged a problem. Diagnosing it tells you what's actually wrong. We do the second thing.
Reading Codes Is Not
the Same as Diagnosing.
A fault code tells you which system logged an event and under what conditions. It doesn't tell you which component failed, whether the component itself is at fault or a sensor monitoring it is, or whether the code is a symptom of something else entirely. A P0420 catalyst efficiency code could be a failed catalytic converter, an oxygen sensor reading incorrectly, an exhaust leak skewing the sensor data, or a fuel trim issue affecting combustion upstream. Parts-swapping based on the code number is how you replace multiple components and still have the light on.
We use dealer-level scan equipment that accesses every module in Subaru's CAN bus network — not just the powertrain codes a generic reader sees. We read live data streams, perform bidirectional component tests, and correlate findings across systems before recommending a repair. You get a clear explanation of what the car is telling us and what we recommend — not a parts list generated by a code number.
- Full-system scan — every module on the CAN bus, not just powertrain
- Live data analysis — sensor readings, fuel trims, misfire counts, and more
- Bidirectional component testing — we confirm function, not just the absence of a fault code
- Plain-language explanation of findings — what the code means, what caused it, what fixes it
- Diagnostic fee credited toward any repair work you authorize with us
What We Diagnose
Every module in your Subaru's network — not just the ones a generic scanner can reach.
Check Engine Light
The most common diagnostic request — and the most commonly mishandled. We read powertrain fault codes, review freeze frame data to understand conditions at the time of the fault, analyze live sensor data to confirm what the code is actually reporting, and verify the repair before clearing the light. We don't clear codes and return the car; we fix the fault that set them.
ABS, Traction & Stability Control
These systems share wheel speed sensor inputs and communicate across modules — a single failed sensor can light up all three simultaneously. Diagnosis requires reading the ABS and VDC modules directly, not inferring from powertrain codes. We identify which wheel speed sensor is at fault, whether the issue is the sensor itself, the tone ring, or the wiring between them, and we verify wheel speed readings in live data before and after repair.
EyeSight & Driver Assistance
EyeSight faults can stem from camera obscuration, voltage irregularities, physical damage to the camera bracket, or calibration drift after windshield or suspension work. We read EyeSight module fault codes directly, distinguish between camera-related faults and upstream electrical causes, and advise on whether a calibration procedure is required. EyeSight warning lights are not always a camera problem — accurate diagnosis prevents unnecessary and expensive camera replacements.
Transmission & CVT
Transmission control module faults, CVT ratio errors, torque converter codes, and shift quality issues. CVT faults in particular require live data analysis — monitoring fluid temperature, input and output speeds, gear ratio, and line pressure simultaneously to understand what the transmission is actually experiencing. A CVT code without live data context leads to premature and expensive transmission replacement on cars that needed a fluid service or a solenoid.
Airbag & SRS
Airbag warning lights require module-level access to diagnose accurately — the SRS module is invisible to generic OBD readers. Common causes include a faulty clock spring (which also causes horn and steering wheel control failure), a seat occupancy sensor, or a fault logged from a previous minor impact. We read the SRS module faults and provide a clear diagnosis rather than recommending airbag component replacement based on guesswork.
Pre-Purchase Scan
A full-system scan before buying a used Subaru surfaces stored codes that were cleared before the sale, pending faults that haven't yet triggered a warning light, and module data that reveals the car's actual history. Combined with our multi-point inspection, it's the most complete picture you can get of a Subaru's condition before committing to a purchase. See our Inspection page for more detail on pre-purchase evaluations.
The Equipment to Read It.
The Knowledge to Understand It.
Dealer-Level Equipment
Generic scan tools read SAE-standard powertrain codes. Subaru's proprietary modules — ABS, SRS, EyeSight, CVT, body control, TPMS — require equipment that speaks Subaru's protocol. Our diagnostic tooling accesses the complete network, reads live data from every module simultaneously, and performs the same bidirectional tests a Subaru dealer would. The difference in diagnostic accuracy is significant.
Plain Language, Every Time
We explain what we found, what it means, and what we recommend — in terms that make sense without a background in automotive electronics. You'll understand the diagnosis before we ask you to authorize a repair. If the finding is a simple fix, we tell you that. If it's complex or expensive, we explain why and give you the information you need to make a real decision.
Diagnostic Fee Applied to Repair
Our diagnostic fee is credited in full toward any repair work you authorize with us. You're not paying twice — the diagnostic cost becomes part of the repair cost. If the diagnosis reveals that the repair isn't cost-effective or isn't something we're the right shop for, you get a straight answer and pay only for the diagnostic time. No obligation, no pressure.
Diagnostics FAQ
My check engine light is on but the car seems to drive fine. Do I need to worry?
It depends on the fault. Some check engine codes indicate conditions that reduce efficiency or increase emissions without affecting drivability — an evaporative emissions leak, for instance, or a minor fuel trim issue. Others indicate active engine or transmission problems that will worsen if ignored and eventually cause damage or leave you stranded. A steady light is lower urgency than a flashing one — a flashing check engine light means an active misfire severe enough to damage the catalytic converter and warrants stopping as soon as it's safe. Either way, reading the code is the first step. Don't clear it and wait.
The auto parts store read my codes for free. Why would I pay for diagnostics?
Parts store code reads retrieve SAE-standard powertrain fault codes — a small subset of the data available from your car. They don't access ABS, airbag, transmission control, body, or EyeSight modules. They read the code number but don't analyze freeze frame data, live sensor values, or cross-module correlations that distinguish the fault from its cause. It's the difference between knowing a smoke alarm went off and knowing what's actually on fire. The free code read is a starting point, not a diagnosis — and acting on it as if it were a diagnosis is how expensive parts get replaced unnecessarily.
My EyeSight light came on after I got my windshield replaced. Are they related?
Very likely yes. The EyeSight stereo camera system is mounted to the windshield and requires calibration after windshield replacement — a procedure that involves a specific target pattern and scan tool calibration routine. If the shop that replaced the windshield didn't perform this calibration, the system will log a fault and disable itself. This is one of the most common EyeSight fault causes we see. The fix is a calibration procedure, not a camera replacement. We perform EyeSight recalibration as a standalone service.
Can you diagnose an intermittent problem that doesn't always act up?
Intermittent faults are the hardest diagnostic challenge — but they're also where thorough module scanning and live data monitoring matters most. Intermittent faults often leave stored fault codes even when the symptom isn't present, and live data can reveal marginal sensor readings or borderline component behavior that hasn't yet crossed the threshold to set an active code. We also use freeze frame data to understand the exact conditions under which the fault occurred, which narrows the cause significantly. If the car is acting up when it arrives, that's ideal. If it isn't, we still have tools to work with.
How long does a diagnostic appointment take?
A full-system scan and initial fault code review takes 30–60 minutes. Deeper diagnostic work — live data analysis, component testing, wiring diagnosis, or chasing an intermittent fault — takes longer and varies by system. We'll give you an honest time estimate when you schedule and keep you updated if the diagnosis is taking more time than expected. For complex electrical faults, plan to leave the car for the day.