Car Diagnostics in Stevenage
We Find the Fault.
We Fix It Right.
Warning light on? Something feels wrong? TGPP Autocare uses state-of-the-art diagnostic equipment to pinpoint exactly what's going on with your vehicle — quickly, accurately, and without guesswork. No unnecessary parts. No inflated bills.
What Our Diagnostics Cover
Our Diagnostic Services
What We Diagnose
We cover the full spectrum of modern vehicle diagnostic work. Every check starts with a clear explanation of what we're looking for and a quote before any further work is agreed.
01 — Foundation Service
Diagnostic Fault Code Check
The starting point for almost every diagnostic investigation
When a warning light appears or something doesn't feel right, a full fault code scan is the essential first step. We connect to your vehicle's OBD port and interrogate every module — engine, transmission, ABS, airbag, body control and more — reading and interpreting all stored and pending fault codes. We then give you a clear, plain-English report of exactly what we found and what it means.
What We Do
- →Full multi-system OBD scan
- →Reading and interpreting all stored and pending fault codes
- →Live data analysis of key sensors and parameters
- →Detailed written report of all findings
What You Get
- →Clear explanation of every fault found
- →Honest advice on what needs fixing and what doesn't
- →Written quote for any recommended repairs
- →No unnecessary work carried out without your approval
04 — Engine
Engine Performance Diagnostics
Misfires, poor economy, loss of power — pinpointed
Beyond simply reading fault codes, we analyse live engine data — fuel trims, sensor behaviour, ignition timing, injector performance — to find exactly what's causing a power loss, rough idle or economy drop.
What We Do
- →Fuel trim and mixture analysis
- →Misfire diagnosis and cylinder balance testing
- →Ignition system and timing analysis
- →Injector performance testing
- →MAF, MAP and lambda sensor analysis
- →Performance data logging under load
05 — Electrical
Electrical System Diagnostics
Battery, charging, wiring, modules and beyond
Modern vehicles are as much computer as car. Electrical faults can be tricky to track down without the right equipment. We test systematically from the battery and charging system through to individual modules and wiring harnesses.
What We Do
- →Battery and charging system testing
- →Alternator load testing
- →Wiring harness inspection and continuity testing
- →Body control module (BCM) diagnostics
- →Parasitic drain testing
- →Component and relay testing
06 — Transmission
Transmission Diagnostics
Auto and manual gearbox issues diagnosed properly
Slipping, rough shifting, delayed engagement or gearbox warning lights — transmission problems are expensive to fix if misdiagnosed. We use specialist tools to read transmission data and identify the fault before any dismantling.
What We Do
- →Gearbox fault code scan
- →Fluid pressure testing
- →Solenoid and valve body testing
- →Transmission performance data logging
- →Clutch pack and torque converter assessment
07 — Safety Systems
ABS & Traction Control Diagnostics
Critical safety systems checked and restored
ABS and traction control faults often share the same wheel speed sensors and modules. A warning light for either system means these safety-critical features may not function correctly in an emergency. Don't drive on a lit ABS light without getting it checked.
What We Do
- →ABS and TCS fault code scan
- →Wheel speed sensor testing
- →ABS pump and modulator testing
- →ABS module diagnostics
- →ESP / stability control diagnostics
08 — Comfort Systems
Air Conditioning Diagnostics
Not blowing cold? Smells odd? We'll find out why
Air conditioning faults range from simple refrigerant loss to compressor failure or electrical issues. We diagnose before we repair — so you're not paying for parts that aren't the actual problem.
What We Do
- →Refrigerant leak detection
- →System pressure testing
- →Compressor testing and clutch check
- →Condenser and evaporator inspection
- →Electrical circuit and control testing
- →R134a and R1234yf regas
09 — Safety Systems
Airbag & SRS Diagnostics
Airbag warning light? Don't ignore it
An illuminated airbag or SRS warning light means the system may not deploy correctly in a collision. This is one of the most important warning lights on your dashboard — it should never be ignored or reset without diagnosing the underlying cause.
What We Do
- →SRS module fault code scan
- →Airbag sensor and clock spring testing
- →Seat belt pretensioner diagnostics
- →Crash data and deployment history check
- →Module replacement and coding
10 — Security
Key Programming & Immobiliser Diagnostics
Can't start? Won't unlock? We can help
Immobiliser faults, lost or damaged keys, and key fob issues can leave you completely stranded. We have the equipment to diagnose immobiliser problems and carry out key programming across most popular makes and models.
What We Do
- →Immobiliser system diagnostics
- →Key fob programming
- →Transponder key coding
- →ECU and BCM security coding
- →Fault code scan and immobiliser reset
11 — Buying a Used Car?
Pre-Purchase Vehicle Inspection
Don't buy a car with hidden problems — get it checked first
Buying a used car is one of the most significant purchases most people make, and a car that looks great can be hiding thousands of pounds worth of faults. Our pre-purchase inspection gives you a full diagnostic picture of a vehicle before money changes hands — potentially saving you from an expensive mistake.
What We Check
- →Full multi-system OBD scan — all fault codes, including hidden and pending
- →Engine live data — misfires, fuel trims, sensor health
- →Battery and charging system test
- →Brake, ABS and suspension check
What You Receive
- →Detailed written report of all findings
- →Clear list of any faults found and their likely cost to fix
- →Honest recommendation on whether the vehicle represents good value
- →Peace of mind — or solid grounds to renegotiate the price
Dashboard Warning Lights
Got a Warning Light On?
Don't ignore a warning light and don't panic either. Most warning lights have a specific meaning that our diagnostic equipment can identify immediately. Here are the most common ones we see — and what they typically indicate.
Engine Cooling System
Engine Oil Pressure
Charging System
Brake System
ABS System
Brake Pad Wear
DPF Fault
Glow Plug System
Engine Management
EPC System
ESP / Stability
Tyre Pressure (TPMS)
Oil Level Low
Suspension Fault
Check Engine / Engine Management
The most common warning light — can indicate anything from a loose fuel cap to a serious fault. Always get it scanned promptly.
Oil Pressure Warning
Low oil pressure can destroy an engine very quickly. Stop safely as soon as possible and do not drive further without having this checked.
Coolant Temperature Warning
Engine overheating is serious. Pull over safely, switch off and let the engine cool. Do not remove the coolant cap. Call us.
Battery / Charging Warning
Indicates a problem with the battery, alternator or charging system. Your vehicle may cut out without warning if ignored.
Brake Warning Light
Could indicate low brake fluid, a handbrake issue, or a serious brake system fault. Don't ignore this — brakes are your primary safety system.
ABS Warning Light
Your ABS system may not function in an emergency stop. Normal braking usually still works, but get it diagnosed promptly.
DPF Warning Light
Diesel particulate filter is blocked or regeneration has failed. A longer motorway run may clear it — but if the light persists, get it scanned.
Airbag / SRS Warning
The airbag system may not deploy in a crash. This is a safety-critical fault — do not ignore it or reset it without diagnosing the cause.
TPMS Warning
One or more tyres are significantly underinflated or the system has a sensor fault. Check pressures first — if the light stays on, we can reset or replace the sensors.
Glow Plug Warning (Diesel)
If this light stays on after starting, one or more glow plugs has failed — making cold starts difficult and potentially causing rough running.
Got a warning light on right now? Don't guess what it means — call us on 01438 232556 or book a diagnostic online and we'll identify the fault quickly, explain it clearly, and give you an honest quote to fix it.
📅 Book a DiagnosticWhy TGPP Autocare
Why Choose Us for Diagnostics?
Good diagnostic work isn't just about plugging in a reader and hoping for an answer. It takes the right equipment, the experience to interpret results correctly, and the honesty to tell you what you actually need.
State-of-the-Art Equipment
We invest in professional-grade diagnostic tools — not generic plug-in readers. The difference is the depth of data we can access, the live parameters we can monitor, and the accuracy of our results.
We Interpret, Not Just Read
Any garage can read a fault code. We analyse what it actually means — cross-referencing live data, sensor behaviour and symptoms to find the real cause, not just the symptom.
RAC Approved Garage
Independently inspected and approved by the RAC every year. Our diagnostic work is carried out to the same exacting standard as every other job — with transparent pricing and a 12-month guarantee.
Plain-English Results
We don't hand you a printout and leave you to Google it. We explain what every fault means, what it's likely to cause if not addressed, and what it would cost us to fix. Then you decide.
No Unnecessary Repairs
We only recommend what's actually needed. Our pricing is transparent before any work begins and nothing is carried out without your approval. No pressure, no upselling.
Fast Turnaround
A diagnostic check is usually completed the same day. We'll tell you what we found, what it means, and what the options are — so you can make a decision quickly and get back on the road.
Warning Light On? Something Feel Wrong?
Don't guess. Book a diagnostic at TGPP Autocare and we'll tell you exactly what's going on — clearly, honestly, and without the jargon. Serving Stevenage and Hertfordshire.