Stop Guessing. Get the Problem Diagnosed Right.
Most mechanics guess.
Terrence diagnoses.
Other shops replace parts and hope for the best. Terrence Blake has been diagnosing vehicles since 1997 — cars, pickups, box trucks, semis. He finds the problem first, then quotes the fix.
Diagnosing
Specialties
Direct-Hit
In-Shop
- 01· Pull live fuel trims, knock data ✓
- 02· Scope coil-on-plug primary signal ✓
- 03· Injector balance · cylinder 6 ●
- 04· Cross-ref Identifix · TSB …
Bring us your hardest problem.
The one nobody else can solve.
These are the calls we get most often — the cars and trucks that have been to two or three shops already. Walk us through the symptom. We'll start at the scan and work back to the cause.
Won't Start
Crank, no fire. We trace the path.
Check Engine Light
Past the code, into the cause.
AC Not Cooling
Pressure tested. Leak located.
Suspension Issues
Knocks, sway, pull — diagnosed.
Transmission Slipping
Fluid, solenoid, or internal.
Engine Misfires
Cylinder isolated. Cause confirmed.
Electrical Issues
Voltage drops. Parasitic draws.
Unknown Symptoms
The "I don't know what it is" call.
We find the problem first.
Then we quote the fix.
Other shops guess and replace until something works — on your dime. Every Big Tee repair starts here, with the same five steps. No skipping. No shortcuts. No assumptions.
Document the symptom
When it happens. What it sounds like. What changed. The story matters before the scan does.
Full system scan
All modules — engine, transmission, ABS, body, chassis. Live data, freeze frames, history.
Isolate with real tools
Scope, multimeter, pressure, smoke, compression. We confirm, we don't assume.
Cross-reference Identifix
Same vehicle, same code, same fix — verified against real-world repair data. No guessing.
Honest, itemized quote
Exact parts. Exact labor. Exact time. You approve before a wrench turns.
Guess. Replace. Repeat.
- Read the code. Replace the part the code names.
- Problem comes back. Replace another part.
- You pay for parts and labor on guesses.
Test. Confirm. Quote.
- Pull codes. Test the system the codes point to.
- Cross-reference against verified repair data.
- Quote the actual fix — once.
Every repair. One mechanic.
From a no-start sedan to a fleet semi. Diagnostic work, scheduled maintenance, and full engine and transmission swaps — done by the same hands. No referrals out.
We come to you.
Driveway, jobsite, parking lot — Terrence arrives in a fully equipped service truck. Diagnostics, brakes, suspension, electrical, AC, and most routine repairs can be completed on-site, often in a single visit.
- Bidirectional scanner + scope on board
- Most common parts stocked in truck
- Same-day appointments when available
Or roll into the bay.
Engine swaps, transmission swaps, suspension overhauls, fleet work. Bigger jobs and heavy diagnostics move into the Decatur shop, where the lift, the press, and the full bench live.
- Full-service bay · cars to semis
- Engine + transmission swap specialist
- Pre-purchase inspections by appointment
Cars to semis. All years.
Most "mobile mechanic" listings stop at passenger cars. Terrence works the full range — sedans, dailies, work trucks, box trucks, semis, and fleets.
Passenger Cars
All makes · all years
Pickup Trucks
1/2 ton · 3/4 ton · 1 ton
Box Trucks
Class 3 - 6 commercial
Semi Trucks
Class 7 - 8 over-the-road
Work Vans
Cargo · service · shuttle
Fleets
Recurring maintenance plans
The case for diagnosis.
The cheapest repair is the one done right the first time. Big Tee runs on professional estimating tools, real diagnostic equipment, and 29 years of pattern recognition.
Pattern recognition at scale
Since 1997. Tens of thousands of vehicles. Most problems Terrence has already solved twice.
Cars to semis — covered
From a no-start sedan to a fleet box truck. One mechanic. No referrals out.
Direct-Hit accuracy
Industry-standard repair database. Your VIN, your symptom, the verified fix.
Real diagnostic tooling
Bidirectional scanners, oscilloscope, smoke machine, pressure testers. Beyond a code reader.
Mobile or in-shop
We come to your driveway, your jobsite, your lot — or roll it into the bay.
Itemized before approval
You see the parts, the labor, the time. Nothing starts until you sign off.
"Two shops told me my transmission was gone. Terrence ran the scan, hooked up the scope, and found a wiring harness rubbing through. Fix was forty dollars. Saved me a four-thousand-dollar replacement."
"My check engine light had been on for a year. Three mechanics couldn't figure it out. Big Tee diagnosed it in forty minutes — bad ground on the engine block. Light's been off for eight months now."
"I run six box trucks. Whatever Terrence quotes, I approve, because the numbers are right and the work holds up. He found a transmission cooler leak on Truck 4 nobody else caught."
Decatur and the east-side metro.
Based in Decatur. Mobile service across the east-side metro. Bigger jobs come into the shop. Not on the list? Call — we cover more than we list.
Straight answers. No filler.
FAQ-001 How do you actually know what's wrong with my vehicle?
How do you actually know what's wrong with my vehicle?
Diagnosis is a process, not a guess. We pull every code from every module, capture live data while the symptom is happening, then confirm with the right physical test — pressure, voltage, scope trace, compression. Identifix Direct-Hit cross-references our findings against thousands of verified repairs on the same vehicle. The answer comes from data, not a hunch.
FAQ-002 What if the problem is electrical?
What if the problem is electrical?
Electrical is where most shops give up and start "throwing parts." That's exactly where Terrence does his best work. Voltage drop testing, parasitic draw isolation, oscilloscope analysis on sensor and signal wires — done in the order an electrical fault actually requires.
FAQ-003 Do you just read codes, or actually diagnose?
Do you just read codes, or actually diagnose?
A code is a starting point — it tells us where the symptom showed up, not why. A P0420 doesn't mean "replace catalytic converter." It can mean a bad O2 sensor, an exhaust leak, an injector issue, or yes — a converter. We test which one it is before we quote the repair.
FAQ-004 How do your estimates work?
How do your estimates work?
Itemized and honest. Each line shows the part, the source, the labor time (verified against Identifix and Mitchell), and the total. You approve in writing before any work starts. If the repair changes mid-job, you hear about it before we proceed — not after.
FAQ-005 Can you work on diesel, semi, or heavy-duty trucks?
Can you work on diesel, semi, or heavy-duty trucks?
Yes — class 3 through class 8. Box trucks, dump trucks, semis, work vans, and fleets are part of regular work. Most "mobile mechanic" listings stop at passenger cars. Big Tee doesn't.
FAQ-006 What does a mobile diagnostic call look like?
What does a mobile diagnostic call look like?
We arrive with a fully equipped service truck. Scan, test, and diagnose on-site. Many repairs can be completed in your driveway. Major work — engine swaps, transmission swaps, suspension overhauls — moves to the shop.
Ready for a real
diagnosis?
Describe the symptom. We'll handle the rest. Mobile in the metro Atlanta area, in-shop in Decatur.