errhive/carsFind a code

The automotive diagnostic field guide

Check engine.
Clear head.

A few characters on a scanner.
A better understanding of what comes next.

Explore a referenceP0300P0420P0171

Reference first. Diagnosis next.

DIAGNOSTIC REFERENCEOBD-II

EXAMPLE TROUBLE CODE

P0300

Random/Multiple Cylinder Misfire Detected

SOURCE CONTEXT

Community code reference

Read the reference

11,786dictionary entries

2diagnostic guides

33vehicle makes

Every reference has a source.See how the guide is built

Vehicle-specific diagnostic guides

The same code.
A different diagnosis.

All diagnostic guides
Audi · P0299 / P029900

Audi A4 P0299: confirm the CAEB wastegate diagnosis

A4 CAEB: distinguish intake faults, sporadic codes and confirmed wastegate wear before replacing a turbocharger.

Read the documented decision points
Porsche · P0299

2015 Porsche Macan Turbo P0299: software or hardware?

Use recorded rpm, engine load and DME version to guide diagnosis before parts.

Read the documented decision points

01 / Your vehicle, your context

Start with your make.

All vehicle makes
ToyotaVolkswagenAudiBMWMercedes-BenzPorscheFordHondaChevroletNissanHyundaiKiaJeepSubaruGMCMazdaLexusRam

Make labels help you find a reference. Year, engine and model documentation determine whether it applies.

02 / From the code library

Small code.
Useful context.

Open the code finder
Generic OBD-II
P0300

Random/Multiple Cylinder Misfire Detected

PowertrainRead the code
Generic OBD-II
P0420

Catalyst System Efficiency Below Threshold Bank 1

PowertrainRead the code
Generic OBD-II
P0171

System Too Lean Bank 1

PowertrainRead the code
Generic OBD-II
P0455

EVAP System Leak Detected - Large Leak

PowertrainRead the code
Generic OBD-II
P0A80

Replace Hybrid/EV Battery Pack

PowertrainRead the code
Generic OBD-II
U0100

Lost Communication With ECM/PCM A

NetworkRead the code

Read the first letter

Four systems.
A place to begin.

A code’s prefix puts the signal in context. Explore the reference by vehicle system.

P

Powertrain

Engine, transmission and powertrain diagnostic references. Exact vehicle and module context still matters.

B

Body

Body-system diagnostic references. Confirm the reporting module and vehicle-specific definition.

C

Chassis

Chassis-system diagnostic references. Read the vehicle warnings before deciding whether to continue.

U

Network

Communication and network diagnostic references. A communication code does not identify a failed module by itself.

03 / More than a make badge

Bring your vehicle into focus.

Explore model guides
Toyota

Camry

2018

V6 high-load misfire evidence.

Model scope & documented context
Toyota

Avalon

2019

V6 high-load misfire evidence.

Model scope & documented context
Ford

F-150

2018

2.7L EcoBoost misfire and lean-code evidence.

Model scope & documented context

Good diagnosis starts with good questions

Read the code.
Keep the context.

The name of a fault is not proof of a failed part. Use the reference to understand the signal, then build the evidence.

Into the field guides
01

Capture the full picture.

Keep the exact code, scan report, symptoms and vehicle details together.

02

Know what the source supports.

Code-definition data and a manufacturer’s model-specific guidance answer different questions.

03

Choose an informed next step.

Start with the documented checks. Understand the limits before buying a part or clearing a code.