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Code pages, how-tos, comparisons and charts, newest first.
- XTOOL D8 vs Autel MK900XTOOL D8 vs Autel MK900BT compared on listing facts: ECU coding, active tests, resets, wireless VCI, topology and protocols, plus a verdict on who buys which.Comparison
- XTOOL D7 vs Autel MK808SXTOOL D7S vs Autel MK808S compared on listing facts: ECU coding, active tests, resets, protocols and updates, with a clear verdict on who should buy which.Comparison
- Why is my check engine light on? The common causes in orderWhy is your check engine light on? The most common causes from a loose gas cap to misfires, what the light means, and how to find the real reason with a scanner.Explainer
- Where is the OBD2 port? Finding the 16-pin connectorWhere is the OBD2 port? On most cars it is under the dash on the driver side near the steering column. Common spots and fixes if a scanner will not power up.How-to
- What ECU coding means and when a DIYer needs itWhat ECU coding is, how it differs from programming and adaptations, which repairs need it, and what kind of scan tool a DIYer needs to do it safely.Explainer
- What is a bidirectional scan tool and do you need oneA bidirectional scan tool sends commands to your car to run active tests and relearns, not just read codes. What it does, examples, and who actually needs one.Explainer
- U0101 code: Lost communication with TCMU0101 means a module stopped hearing from the transmission control module. Learn the common causes, how to diagnose the network, and if it is safe to drive.Fix
- U0100 code: Lost communication with ECM/PCM AU0100 means a module lost contact with the engine computer on the vehicle network. Causes, from a weak battery to CAN wiring faults, and how to diagnose it.Fix
- U0001 code: High speed CAN communication busU0001 means a fault on the high speed CAN network that lets modules talk. Learn the symptoms, common wiring and module causes, and how to diagnose it safely.Fix
- TPMS relearn: the three methods and when each appliesTPMS relearn explained: auto, stationary and OBD relearn methods, when your car needs one, and why the TPMS light stays on after a tire rotation or new sensor.How-to
- Topdon ArtiDiag Pro vs Autel MK808STopdon ArtiDiag Pro vs Autel MK808S compared on listing facts: bidirectional tests, ECU coding, service functions and gateway access, with a clear verdict.Comparison
- Scan tool updates and subscriptions: what you pay after year oneDo Autel and other scanners require a subscription? Update terms differ by brand and model. What updates add, what happens when they lapse, and how to update.Explainer
- Readiness monitors explained: how to pass an emissions testWhat OBD2 readiness monitors are, why a car shows not ready for an emissions test, how many incomplete monitors are allowed, and how to get them to complete.Explainer
- P2263 code: Turbo/supercharger boost system performanceP2263 means actual boost does not match what the engine computer expects. Learn the common causes, how to test for boost leaks, and how to fix it.Fix
- P0705 code: Transmission range sensor circuitP0705 means the computer got an invalid signal from the transmission range sensor. See the symptoms, causes, how to test it and the safety risks of driving.Fix
- P0606 code: Control module processor faultP0606 means the engine computer found an internal processor fault. Learn the common causes, from low voltage to software, how to diagnose it, and next steps.Fix
- P0496 code: EVAP flow during non-purge conditionP0496 means fuel vapor is flowing to the engine when the purge valve should be closed. Learn the causes, how to test the purge valve, and how to fix it.Fix
- P0456 code: Evaporative emission system small leak detectedP0456 means the EVAP system found a very small vapor leak. Learn the common causes, how to find the leak, and whether it is safe to keep driving.Fix
- P0455 code: Evaporative emission system large leak detectedP0455 means the EVAP system found a large leak. Learn the common causes, starting with the gas cap, how to diagnose it, and how urgent it is.Fix
- P0449 code: EVAP vent valve/solenoid circuitP0449 means the computer sees an electrical fault in the EVAP vent valve circuit. See the symptoms, common causes, how to test it, and how to fix it.Fix
- P0446 code: EVAP vent control circuitP0446 points to the EVAP canister vent valve or its circuit. Learn what it means, the common causes, how to diagnose it with a scan tool, and how to fix it.Fix
- P0442 code: Evaporative emission system small leak detected (0.040 in)P0442 means the EVAP system found a small leak. Learn the common causes, how to find the leak, what a scan tool shows, and whether it is safe to drive.Fix
- P0420 vs P0430: bank 1 and bank 2 catalyst codesP0420 and P0430 mean the same thing on different sides of the engine. How to find bank 1 and bank 2, what causes each code, and what to check first.Comparison
- P0420 code: Catalyst system efficiency below threshold (bank 1)P0420 means the bank 1 catalytic converter is not cleaning exhaust as well as it should. Causes, how to diagnose it, how to fix it, and whether you can drive.Fix
- P0401 code: EGR flow insufficientP0401 means the engine computer saw too little exhaust gas recirculation flow. Common causes like carbon-clogged passages, how to diagnose it, and how to fix it.Fix
- P0340 code: Camshaft position sensor A circuit (bank 1)P0340 means the computer is not getting a valid signal from camshaft position sensor A on bank 1. See the symptoms, causes, tests and whether you can drive.Fix
- P0335 code: Crankshaft position sensor A circuitP0335 means the engine computer has a problem with the crankshaft position sensor signal. Learn the symptoms, causes, how to test it, and if you can drive.Fix
- P0325 code: Knock sensor 1 circuit (bank 1)P0325 means a problem in the knock sensor 1 circuit. Learn the symptoms, common causes, how to test the sensor and wiring, and whether you can keep driving.Fix
- P0301 code: Cylinder 1 misfire detected (also P0302-P0306)P0301 to P0306 mean a misfire in one specific cylinder. Learn how to read the cylinder number, run a swap test, find the cause and fix it safely.Fix
- P0300 code: Random/multiple cylinder misfire detectedP0300 means the engine is misfiring in more than one cylinder or at random. See the causes, how to diagnose it, and why a flashing light means stop driving.Fix
- P0299 code: Turbocharger/supercharger underboostP0299 means the turbo or supercharger is making less boost than the engine computer expects. Causes, how to diagnose boost leaks, fixes, and driving advice.Fix
- P0174 code: System too lean (bank 2)P0174 means bank 2 is running lean and fuel trims have maxed out. Common causes, how to read fuel trims to find the problem, and how to fix it.Fix
- P0172 code: System too rich (bank 1)P0172 means bank 1 is running rich and the computer cannot pull enough fuel. Learn the symptoms, common causes, how to read fuel trims, and how to fix it.Fix
- P0171 code: System too lean (bank 1)P0171 means bank 1 is running lean. Learn what causes it, how to read fuel trims to find the problem, how to fix it, and whether it is safe to drive.Fix
- P0141 code: O2 sensor heater circuit (bank 1 sensor 2)P0141 means the heater in the downstream O2 sensor on bank 1 has a circuit problem. What it means, common causes, how to test it, and how to fix it.Fix
- P0135 code: O2 sensor heater circuit (bank 1 sensor 1)P0135 means a fault in the upstream O2 sensor heater circuit on bank 1. Learn the causes, how to test the fuse, heater and wiring, and how to fix it.Fix
- P0128 code: Coolant thermostat below regulating temperatureP0128 means the engine takes too long to warm up, usually from a thermostat stuck open. Learn the symptoms, causes, how to test it, and how urgent it is.Fix
- P0118 code: Engine coolant temperature sensor circuit highP0118 means the coolant temperature sensor signal is too high, so the PCM sees a very cold engine. Learn the causes, how to test it, and how to fix it.Fix
- P0101 code: Mass air flow sensor circuit range/performanceP0101 means the MAF sensor reading does not match what the computer expects. See the symptoms, common causes like a dirty MAF or air leak, tests and fixes.Fix
- P0016 code: Crankshaft/camshaft position correlation (bank 1 sensor A)P0016 means the crank and cam position signals do not line up on bank 1. Learn the causes, from low oil to timing chain wear, and how to diagnose it.Fix
- P0014 code: Camshaft position B timing over-advanced (bank 1)P0014 means the bank 1 exhaust camshaft is more advanced than the computer commanded. Learn the causes, from low oil to a stuck VVT solenoid, and how to fix it.Fix
- P0011 code: Camshaft position A timing over-advanced (bank 1)P0011 means bank 1 intake cam timing is more advanced than commanded. Learn the causes, from low oil to a sticking oil control valve, and how to fix it.Fix
- OBD2 scanner vs code reader: what the difference means for youA code reader reads and clears engine codes. A scanner adds live data and more systems, and a bidirectional scanner runs active tests. Which one you need.Comparison
- OBD2 scanner says no link or won't connect: what to checkOBD2 scanner says no link or won't connect? Check ignition, the port fuse, pins, battery voltage, protocol support and Bluetooth pairing in this order.Fix
- OBD1 vs OBD2: which your car has and which scanner worksOBD1 vs OBD2 explained: how to tell which your car has, why an OBD2 scanner cannot read OBD1, and what to use for pre-1996 cars instead.Explainer
- Launch X431 PRO Elite vs Autel MS906 ProLaunch X431 PRO3 V+ Elite vs Autel MS906 Pro compared from listing facts: J2534, ECU coding, services, screen, battery and price, with a clear verdict.Comparison
- Innova 7111 vs Autel MK808SInnova 7111 vs Autel MK808S compared from the listings: bidirectional tests, services, coverage, repair app and price. See which scan tablet suits your garage.Comparison
- How to use an OBD2 scanner, step by stepHow to use an OBD2 scanner: find the port, connect with the key on, read codes and freeze frame, check monitors, and decide what to fix before you clear anything.How-to
- How to read OBD2 codes and what each character meansLearn how to read OBD2 codes: what the letter and four digits mean, generic vs manufacturer codes, and how to look up any code before you buy parts.How-to
- How to clear a check engine light the right wayHow to clear OBD2 codes and reset the check engine light: read and record first, fix the cause, clear with a scanner, then drive so monitors complete.How-to
- Fuel trims explained: short term, long term and what's normalFuel trims explained: what short term and long term fuel trim mean, what numbers are normal, and how to use them to find vacuum leaks and fuel problems.Explainer
- Freeze frame data explained: what the snapshot tells youFreeze frame data is the snapshot your car saves when a code sets. Learn what each value means and how to use RPM, load, temperature, and fuel trims to diagnose.Explainer
- How long to drive after clearing codes before an inspectionHow long to drive after clearing codes before inspection: what a drive cycle is, why it varies by make, and how to check readiness monitors with a scanner.How-to
- Check engine light solid vs flashing: what each meansA solid check engine light means a fault was stored. A flashing light means an active misfire that can damage the catalytic converter. What to do for each.Comparison
- Check engine light on but the car runs fineCheck engine light on but the car runs fine? Here are the usual causes, how to read the code, and when it is still worth fixing soon even with no symptoms.Fix
- Check engine light after getting gas: the gas cap and EVAP codesCheck engine light after getting gas? A loose or worn gas cap often sets an EVAP leak code. How to confirm it, what codes to expect, and when it is something else.Fix
- Can you drive with the check engine light on?Can you drive with the check engine light on? Solid usually means drive carefully and scan soon; flashing means pull over. What to check and what to do next.Explainer
- Battery registration after replacement: which cars need itBattery registration tells a car's charging system a new battery is installed. Which cars need it, including BMW, what happens if you skip it, and how to do it.Explainer
- Autel vs Topdon scanners compared tier by tierAutel vs Topdon scan tools compared tier by tier: entry all-system scanners, bidirectional tools with coding, and pro tablets, with listing specs and a verdict.Comparison
- Autel vs Launch scanners: how the two lineups match upAutel vs Launch scan tools compared tier by tier: entry all-system scanners, bidirectional mid-range tools and pro tablets, with listing specs and a verdict.Comparison
- Autel TS508WF vs TS408 TPMS toolsAutel TS508WF vs TS408 compared from the listings: sensor activation, relearn options, MX-Sensor programming, updates and price, with a clear verdict.Comparison
- Autel MS906 Pro vs MK900: when MaxiSys makes senseAutel MS906 Pro vs MK900BT compared from the listings: ECU coding, services, active tests, hardware and price, plus who should pay for the MaxiSys tablet.Comparison
- Autel MK900 vs Launch CRP919XAutel MK900BT vs Launch CRP919X compared on listing facts: active tests, services, ECU coding, wireless VCI and protocols, with a clear verdict on who buys which.Comparison
- Autel MK808S vs MX808S: what the extra money buysAutel MK808S vs MX808S compared on listing facts: bidirectional tests, services, hardware and TPMS programming, plus who should pay more for the MX808S-TS.Comparison
- Autel MK808S vs MK900: is the upgrade worth itAutel MK808S vs MK900BT compared on listing facts: Bluetooth VCI, CAN FD and DoIP, active tests and services, plus who should pay for the upgrade.Comparison
- Ancel FX6100 vs Autel MK808SAncel FX6100 vs Autel MK808S compared from listing facts: bidirectional tests, service resets, updates, coverage and price, with a verdict on which to buy.Comparison
- Airbag light on: what it means and what not to doAirbag light on? The SRS system has found a fault and the airbags may not deploy. Common causes, how to read SRS codes safely, and why repairs belong with a pro.Fix
- ABS light on: common causes and how to read the codeABS light on? The common causes, from wheel speed sensors to low brake fluid, whether it is safe to drive, and how to read ABS codes with the right scanner.Fix