Support · Fault Code Lookup

OBD-II Fault Code Guides

Mechanic-written repair guides for every trouble code — what it really means, what actually causes it, and how to fix it before you replace expensive parts.

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P2402 Code That Cold-Start Rattle Is the EVAP Pump, Not a Leak P0236 Code Lost Boost on Your EcoBoost? Check Vacuum First P0351 Code Cylinder 1 Won't Spark — Here's the 5-Minute Test P2099 Code Sensor Reads Rich, But the Trim Is the Real Story P2271 Code Skip the O2 Sensor — Inspect the Catalyst First P2509 Code 9 Times Out of 10, It's the Battery — Not the PCM P2196 Code Why a New O2 Sensor Often Won't Fix It P0742 Code Why Your Car Stalls & How to Fix It P0449 Code Check for Spider Webs Before Buying Any Part P0368 Code That Long Crank on Chrysler V6/V8 Engines, Fixed P0354 Code The "D" Is Cylinder 4 — Start Here Before Buying P0328 Code Why GM 5.3L Vortec Owners See This So Often P0133 Code It's Often an Exhaust Leak, Not the O2 Sensor P0036 Code A $15 Fuse Before a $150 O2 Sensor P061A Code Fix It Without Replacing Your PCM P2004 Code The $20 Plastic Lever That Saves a $4,000 Engine P0191 Code Your Fuel Pressure Is Lying to the PCM (or Vice Versa) P2723 Code Stuck in Limp Mode? Fix It Without Rebuild P0420 Code Catalyst System Efficiency Below Threshold P2407 EVAP Leak Can You Fix It Yourself? (Toyota Prius) P203B on BMW E90 The Cheap Fix Shops Often Skip P257D Throttle Fault What It Actually Costs to Fix (Audi A3 8P) P2176 Code Throttle Actuator Control System — Idle Position Not Learned — Don't Replace Your Throttle Body Yet P0595: Cruise Control Servo Control Circuit/Open — What It Really Means P0070 Nissan Teana J32 Ambient Air Temp Sensor Fix P0196 Code Engine Oil Temperature Sensor Range/Performance — Don't Replace Your Sensor Yet P0748 Code Pressure Control Solenoid A Electrical — Don't Replace Your Transmission Yet P2231 Code O2 Sensor Positive Current Control Circuit Range/Performance — Don't Replace Your O2 Sensor Yet P257F Code Idle Air Control Performance — Don't Replace Your Throttle Body Yet P219D Code Cylinder 2 Air/Fuel Imbalance — Don't Replace Your O2 Sensor Yet P0472: Exhaust Pressure Sensor Circuit Low Input | Fast Fix with ICARZONE UR1000 P2107 Throttle Actuator Circuit Open Fix with ICARZONE UR1000 P0428 — Catalyst Temperature Sensor High Voltage (Bank 1, Sensor 1) Diagnose P1447 EVAP System Purge Flow Monitoring Malfunction with ICARZONE UR1000 P0137 Code O2 Sensor Low Voltage – Fix & Cost P0141 Code O2 Sensor Heater Circuit Malfunction P0604 Code Fix 60% Are Battery or Wiring, Not PCM Hardware P0411 Code Find the Secondary Air Flow Failure P2005 Code Fix Intake Manifold Runner Control Stuck Open (Bank 2) Fix P0440 Evaporative Emission Control System Malfunction with ICARZONE UR1000 Fix P0708 Transmission Range Sensor Circuit High Input with ICARZONE UR1000 Fix P0729 Torque Converter/Brake Switch B - Performance/Stuck Off with ICARZONE UR1000 Diagnostic Tool Fix P2102 Throttle Actuator Control System - Stuck Closed with ICARZONE UR1000 Diagnostic Tool Fix P2177 System Too Lean Off Idle Bank 1 with ICARZONE UR1000 Diagnostic Tool Fix P2048 Reductant Delivery Module Performance with ICARZONE UR1000 Diagnostic Tool Fix P0217 Engine Over Temperature Condition with ICARZONE UR1000 Diagnostic Tool P1400 Code Meaning Varies by Make—Diagnose It Correctly P0422 BMW 3 Series (F30/F31) Fix Catalytic Converter Efficiency with ICARZONE UR1000 P2033 Code Ford F-150 10R80 (2017-2023) Fix EGR Temp Sensor with ICARZONE UR800 P0454 Code in Audi Q3 2019-2024 Fix EA888 Gen4 EVAP Fault with ICARZONE UR800
655 codes · page 4 of 14
01 Read your code

Every code is four signals in five characters.

P
System
P = Powertrain (engine & transmission)
0
Type
0 = generic SAE standard · 1 = make-specific
4
Subsystem
The subsystem the code points to
2
Fault
The specific fault
0
Index
Index within that subsystem
P
Powertrain

Engine, fuel, ignition, emissions and transmission. By far the most common — most check-engine lights start with P.

B
Body

Interior comfort and safety: airbags, lighting, power windows, seats, climate control.

C
Chassis

Mechanical systems outside the body: ABS, traction control, steering, suspension, wheel-speed sensors.

U
Network

Communication between control modules over the car's data bus (CAN). Often points to wiring or a module that has gone quiet.

Generic vs manufacturer-specific: a 0 in the second position means the code follows the SAE standard and means the same on every car — those are the ones in this library. A 1 (and sometimes 3) means the carmaker defined it themselves, so the same code can mean different things on a BMW and a Toyota. For those, read the exact definition on your scan tool.

02 When the light comes on

Four moves, in order.

  1. Is it flashing?

    A flashing check-engine light usually means an active misfire that can damage the catalytic converter — ease off the throttle and get it looked at promptly. A steady light is rarely an emergency; investigate soon.

  2. Scan for the codes

    Plug in a scan tool and read the stored codes. Note every code and its freeze-frame data — the first one set is often the root cause of the rest.

  3. Look it up

    Search the code here to understand what system it points to, how serious it is, and the parts most often behind it — before you spend a cent on parts.

  4. Fix, clear, confirm

    Repair the root cause, clear the code, then drive and re-scan. If it comes straight back, the underlying fault is still there — keep diagnosing, don't just keep clearing.

From code to cause

A code tells you the system. A scanner tells you the part.

Reading the code is step one. ICARZONE tools go further — live data, bidirectional actuator tests and OE-level access pinpoint the actual faulty component, then clear the code once it's fixed.

Explore the toolsCompare models

Can't find your code, or got a P1/B1/C1/U1 code? Those are manufacturer-specific. Tell our team the code and your vehicle (make, model, year) and we'll help you read it — or grab the exact OE definition with an ICARZONE tool. Contact support →