P CODE FAMILY

Powertrain code references — Page 13.

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

Generic OBD-II

P04B4

These are code references, not a list of confirmed faults on every vehicle. Read the source and applicability notes, then match the exact vehicle, year, engine and scan report.

Refueling Vapor Control Valve Stuck Closed

F-150 PowerBoost fuel-door latch checks before deeper diagnosis

Cherokee stored fuel-door fault and false-setting logic

Fuel Fill Door Position Sensor/Switch Circuit Intermittent/Erratic

fuel-door position has entered an invalid signal band

fuel-door position feedback is below its allowed range

fuel-door position feedback is above the calibrated limit

fuel-door lock driver reports an electrical fault

the commanded fuel-door lock transition did not occur

Fuel Fill Door Lock Control Circuit Low

Fuel Fill Door Lock Control Circuit High

Fuel Fill Door Unlock Control Circuit/Open

fuel-door unlocking failed to produce the expected transition

Fuel Fill Door Unlock Control Circuit Low

Fuel Fill Door Unlock Control Circuit High

fuel-door lock position has an invalid electrical reading

fuel-door lock feedback changed without an unlock command

lock-position signal is low rather than simply unlocked

high lock-position feedback can represent an open circuit

Fuel Fill Door Lock Position Sensor/Switch Circuit Intermittent/Erratic

fuel-door open-request switch reports an invalid signal

Fuel Fill Door Open Request Sensor/Switch Performance/Stuck Off

a low refuel-request signal is different from a stuck fuel door

fuel-door request input is electrically high

Fuel Fill Door Open Request Sensor/Switch Circuit Intermittent/Erratic

Fuel Fill Door Open Request Sensor/Switch Stuck On

EGR Temperature Sensor C Circuit

low-pressure EGR temperature disagrees after an overnight soak

upstream low-pressure EGR temperature resistance too low

EGR temperature raw resistance above the high boundary

intermittent upstream low-pressure EGR temperature behavior

Exhaust Brake Input Circuit

Exhaust Brake Input Circuit Range/Performance

Exhaust Brake Input Circuit Low

Exhaust Brake Input Circuit High

Exhaust Brake Input Circuit Intermittent/Erratic

Excessive Time To Enter Closed Loop EGR Control

Low EGR flow reaches the closed-loop control limit

Excessive EGR flow is detected as a control-ratio error

Crankcase ventilation judged by pressure offset and pulsation

Fuel Fill Door Position Sensor/Switch Circuit Range/Performance

cold-start EGR insufficient flow uses an operating-point-dependent limit

cold-start EGR excessive flow compares modeled and measured air mass

bank-1 purge-valve response during intrusive testing

EVAP System Purge Control Valve A Stuck Closed

Crankcase Ventilation Hose Connection Sensor Circuit

PCV hose pressure signal low from an open or ground short

PCV hose pressure output above its electrical ceiling

Crankcase Ventilation Hose Connection Sensor Circuit Intermittent/Erratic

EGR Temperature Sensor D Circuit

EGR Temperature Sensor D Circuit Range/Performance

EGR Temperature Sensor D Circuit Low

EGR Temperature Sensor D Circuit High

EGR Temperature Sensor D Circuit Intermittent/Erratic

EVAP System Small Leak Detected - Fuel Tank Side

EVAP System Small Leak Detected - Fresh Air Side

EVAP System Large Leak Detected - Fuel Tank Side

EVAP System Large Leak Detected - Fresh Air Side

Wrangler tank-side leak from a trapped cap tether

EVAP System Very Small Leak Detected - Fresh Air Side

High-load EVAP purge behavior is tested under boost

EVAP System Purge Line Performance

Catalyst Heater Supply Voltage Bank 1

Catalyst Heater Supply Voltage Bank 2

Catalyst Heater Circuit Low Bank 1

Catalyst Heater Circuit Low Bank 2

Catalyst Heater Circuit High Bank 1

Catalyst Heater Circuit High Bank 2

Catalyst Heater Circuit Intermittent Bank 1

Catalyst Heater Circuit Intermittent Bank 2

high-pressure EGR drive electronics overtemperature

PCV pressure should approach atmosphere after engine rotation stops

Chrysler 300 crankcase-ventilation performance software case

EGR Actuator A Control Processor Performance

Catalyst Heater Circuit Performance Bank 1

Catalyst Heater Circuit Performance Bank 2

A diesel vehicle-speed code can describe missing CAN information

An implausibly high vehicle-speed report in a manual-transmission example

Two vehicle-speed paths disagree in the Duramax monitor

Abrupt transmission output-speed changes need context