P0842 and P0843: transmission fluid pressure sensor A circuit
Before believing the gearbox has lost pressure, check the instrument that measured it. A faulty sensor turns a healthy transmission into an expensive quote.
OBD-II · AI · Cloud
Car Diagnostics Platform
On-board OBD-II diagnostics with cloud analytics, AI assistant and fleet support.
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Articles on diagnostics, OBD-II and car maintenance
Isuzu D-Max and SsangYong/KGM: diesel OBD diagnostics
Working diesels bought for towing and load carrying. The emissions hardware is the recurring cost, and the drivetrain oils are the recurring omission.
P2031 to P2036: exhaust gas temperature sensor bank 1 sensor 2
A modern diesel carries several exhaust temperature sensors along its after-treatment system. Which one has failed determines what stops working.
P2195 and P2197: oxygen sensor signal biased or stuck lean
The sensor is not out of range and not dead. It is simply not moving the way a working sensor moves, and the ECU has noticed the difference.
Kia and Hyundai Common OBD-II Codes: Sportage, Tucson, i30, Ceed
Top DTC codes for Kia Sportage, Ceed, Hyundai Tucson, i30: Theta II engine failures, GDI direct injection carbon buildup, DCT wet clutch, P0011 CVVT — OBD-II diagnostics.
Turbocharger Boost Leak Diagnostics via OBD-II: P0299, P0234, Boost Live Data
How to detect boost leaks and turbocharger faults through OBD-II: P0299 underboost, P0234 overboost, Boost Pressure Live Data — systematic leak-finding algorithm without expensive equipment.
P0121 to P0123: throttle position sensor circuit faults
On a drive-by-wire engine the throttle sensor is a safety-critical input, which is why these codes send the car into limp mode rather than tolerating an error.
Water in the spare wheel well: seals, lights and drains
The lowest point in the boot collects everything that gets in. Finding the entry point is a systematic job, and the well itself is rarely the problem.
Wipers stop mid-screen: park switch and linkage
Blades that stop halfway up the glass instead of returning to the bottom point at one specific mechanism, and the fix is usually cheaper than the motor.
Subaru EJ Engine OBD Diagnostics: Outback, Forester, Impreza, WRX
OBD-II diagnostics for Subaru EJ20/EJ25 boxer engines: P0301 head gasket misfires, P0420/P0430 cats, STI flat-six knock detection, AWD DCCDcodes — complete guide.
Whistling from the engine bay: leak, bearing or belt
Three very different faults produce a whistle, and they are distinguishable by when the noise appears. That timing is most of the diagnosis.
Buying a car with LPG: what to check besides the gas equipment itself
Everyone inspects the gas system. Few check what it did to the engine over a hundred thousand kilometres — and that is where the difference between a good buy and an expensive repair lives.
What our users actually find
Check Engine on for 2 months
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Before: shop wanted $400 to replace the catalytic converter.
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After: scanned → P0420. Turned out to be a $15 oxygen sensor. Light stayed off.
Diesel lost power
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Before: no idea whether it's the DPF, EGR or an injector. Shop suggested "full diagnostics" for $180.
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After: P0401 — insufficient EGR flow. Cleaned the valve at home, power returned.
Battery drained every morning
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Before: a new battery didn't help. Electrician muttered about "wiring issues".
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After: U0140 — lost communication with BCM. Corroded terminals; cleaned them, problem solved.
Rough idle on a Corolla
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Before: mechanic suggested a full engine overhaul. Vibration at idle, no clear cause.
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After: P0303 — misfire on cylinder 3. Replaced one spark plug for $4. Idle smooth again.
Fuel consumption doubled
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Before: replaced filters, O2 sensor, injectors — nothing helped. Burning 14 L/100 km.
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After: P0171 — lean mixture, MAF out of range. Cleaned the sensor — dropped to 8 L/100 km.
Automatic jerked on 2nd gear
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Before: shop quoted a $900 transmission rebuild. Symptoms: jolts during acceleration.
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After: P0715 — turbine speed sensor. $35 part, 30-minute job. Jerking gone completely.
Engine overheated on the highway
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Before: replaced the radiator and coolant — temperature still crept up on long drives.
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After: P0128 — thermostat stuck open. $18 replacement fixed it; temp stays normal.
Fuel smell inside the cabin
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Before: mechanics shrugged. One suggested replacing the fuel tank — $400.
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After: P0456 — small EVAP leak. A cracked $6 nipple was the culprit. Smell gone.
ABS triggered on dry pavement
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Before: brakes checked twice — everything fine. ABS still kicked in randomly.
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After: C0035 — front left wheel speed sensor faulty. $22 replacement, no more false ABS.
Wouldn't start after rain
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Before: cranked fine but no start every rainy day. New plugs and coil did not help.
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After: P0335 — crankshaft position sensor with damaged insulation. $28 fix, starts every time.
Engine hesitated during overtake
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Before: tuning shop offered an ECU remap for $220. Power fell off sharply at 3000 rpm.
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After: P0101 — MAF out of range. $45 sensor swap. Acceleration became smooth and strong.
AC stopped cooling
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Before: recharged refrigerant 3 times in one summer — $120 wasted, lasted a week each time.
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After: P0530 — AC pressure sensor faulty. $16 part, no more leak, cold air all summer.
Sample scenarios based on common cases — real customer quotes will appear once we collect publication consent.
Saw a trouble code on your dashboard?
Enter the DTC and find out what it means, how severe it is and what causes it.
View all 150 popular codesOne platform, three use cases
DIY driver
You own the car and want to know what "Check Engine" means before the shop. Quick sessions from the phone, per-car history, plain-language AI explanations.
Personal tierShop mechanic
You own or work in a small garage. Web panel with concurrent sessions, branded PDF reports for customers, DTC library with explanations.
Pro tierFleet manager
You run 10 to 500+ vehicles. Roles and permissions, automatic alerts on critical DTCs, cross-vehicle comparison, exportable reports.
Fleet tierThe whole story on one screen
DTC + plain-English explanation
Why the light came on, how serious it is, and what to do next — no jargon.
Live telemetry
RPM, coolant temp, MAF, throttle — in real time, like a factory service manual.
AI assistant
Describe the symptom — the model cross-checks ECU data and suggests the likely cause.
How much you'll save per year
Shop diagnostic visits
$60 – $120 × 2–3 times/year
≈ $180 – $360
App + ELM327 adapter (one-off)
≈ $10 (adapter) + subscription from $3/month
≈ $46 / year
Difference
≈ $130 – $310 per year
Estimate for a single-car driver who deals with 2–3 unexplained warnings a year. Your savings depend on how often things go wrong.
Will your car work?
OBD-II is mandatory on passenger cars (USA since 1996, EU since 2001) and on light commercial vehicles (since 2005).
Yes, your car is supported
You need an ELM327-based OBD-II adapter (Bluetooth Classic SPP) — from $10–15. Pair and start a session.
Limited support
Your car may use a non-standard OBD-II variant. Try it — the app auto-detects the protocol (ISO 15765, KWP2000, ISO 9141).
Not supported
Before 1996 (US) / 2001 (EU) cars used OBD-I with a different connector and protocol. OBD-I is not supported.
What AI diagnostics looks like on a real code
- 01
What the scan sees
DTC P0301 confirmed, live data shows a +12% Long-Term Fuel Trim spike on cylinder 1, brief misfires under load.
- 02
What the AI says
Most likely cause — cylinder 1 ignition coil (44%), then spark plug (28%). Injector — 15%, compression — 10%. Recommendation: swap the coil first; the AI predicts P0301 will clear within 3 cold starts.
- 03
What to do next
Coil ~$45, 20-min DIY or ~$30 labour at a shop. Vs. a $150 scan-and-guess shop diagnostic — getting the right part first saves time and money.
Illustrative example — real findings depend on your car.
How our AI diagnostics work
Specialized knowledge base
Approximately 145,000 DTC codes with expert descriptions, stored server-side — never bundled into the mobile app. The AI is grounded in this data rather than answering from general training knowledge.
RAG: retrieval-augmented generation
A dedicated retrieval service backed by a vector database with text embeddings. Relevant technical material is retrieved and injected into the model context before it answers — the model does not answer from its general training knowledge alone.
The model
A large commercial language model accessed through a model-routing abstraction layer, so the provider can be swapped without altering the diagnostic pipeline.
Thin client by design
The mobile app is an Apache Cordova shell with a React UI layer. The diagnostic session is server-owned: the phone acts as a transparent proxy, not the decision-maker. Logic lives once, server-side — auditable and upgradable without an app-store release cycle.
- 1900+ DTC codes explained
- 1996+ Years of OBD-II vehicles
- 8 AI agents for diagnostics
What we won't do
No ECU flashing without consent
We read parameters and DTCs (Mode 01, 03, 09) — passive queries only. Writing to the ECU only happens with explicit consent and a risk disclosure.
We recommend a shop when needed
When a code points to pressurized fuel systems, brakes or airbags, the AI plainly says "go to a shop" — instead of pushing DIY to keep you subscribed.
No fake urgency, no upsell scripts
No "3 seats left" or "special price today". The tier price is the same tomorrow as it is now.
Quick answers
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Do I need to buy anything besides the app?
Yes, an OBD-II adapter on the ELM327 chip (Bluetooth Classic SPP) — starts around $10. We do not sell adapters, but we maintain a compatibility list in the docs.
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Which vehicles are supported?
All cars and light commercial vehicles with an OBD-II port — mandatory since 1996 in the US, 2001 in the EU. Heavy trucks on J1939 are on the roadmap.
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Is connecting to the ECU safe?
Reading data (Mode 01, 03, 09) is fully safe — passive queries only. Clearing DTCs (Mode 04) is safe but requires explicit confirmation. We do not perform write operations without certification.