DOCUMENTED DIAGNOSTIC CONTEXT

Diagnostic code articles — Page 9.

Understand what the recorded fault means, which findings change the diagnosis, and what the cited documentation can confirm. Each article states the system or vehicle scope it covers.

Some sources leave details unresolved. Those articles include a visible source note; a code match alone does not establish applicability to your vehicle.

Secondary-air flow compared with a pressure-based model

Secondary-air valve circuit feedback versus command

a small current threshold identifies an open secondary-air valve circuit

Audi's air-valve fault is evaluated as a ground-short voltage

valve B's open-circuit code needs electrical path identification

the CTUA valve-B fault points to a low electrical signal

Secondary-air pump control is an electrical test

EGR temperature fails a post-soak response check

low-range EGR temperature feedback depends on sensor type

high-range EGR temperature circuit evidence

erratic EGR temperature changes between samples

AIR valve circuit low during an off command

Catalyst oxygen storage measured through a controlled mixture change

diesel oxidation-catalyst efficiency during regeneration

This catalyst efficiency check depends on an eligible regeneration event

high-pressure EGR remains open after drive removal

EGR stuck closed uses actuator-position evidence rather than flow alone

bank-2 catalyst oxygen-storage assessment

bank 2 warm-up catalyst efficiency and the firmware branch

main catalyst bank 2 efficiency needs exhaust and sensor evidence

Excess vacuum across the EVAP pump's reference orifice

Too little reference vacuum in an EVAP leak-detection check

Altima small-leak testing requires a working vent seal

when Titan purge flow fails the pressure-response check

A small EVAP leak judged against a measured reference opening

Purge-valve open-circuit logic in a row marked disabled

Titan purge-valve circuit open and the low-voltage branch

why Titan purge-solenoid high feedback needs circuit diagnosis

Vent restriction detected while purge operates normally

Titan vent-valve electrical fault versus a valve left open

Volkswagen EVAP vent circuit short classification

The EVAP vent open-load fault can arrive as a CAN status message

low-pressure EGR position signal below electrical range

upper-range low-pressure EGR SENT feedback

AIR valve voltage high when commanded on

Maxima EVAP pressure sensing includes its hose connection

Fuel-tank pressure compared with the leak-pump pressure sensor

Fuel-tank pressure voltage below the electrical lower limit

Fuel-tank pressure voltage exceeds the permitted signal range

An apparent refueling event caused by an unstable pressure signal

Weak EVAP vacuum can mean a large leak or a purge blockage

A small EVAP leak can be detected after the engine is switched off

A refueling event changes the interpretation of an EVAP gross-leak result

Purge-solenoid control output low while the driver is off

Purge-solenoid high feedback during an active low-side command

low-pressure EGR command circuit open-load evidence

low-pressure EGR position tracking outside tolerance

low-pressure EGR short-to-ground indication during drive

low-pressure EGR command short toward the power supply

low-pressure EGR does not return to its closed default

Volkswagen CJAA low-pressure EGR stuck-closed monitor

A broad fuel-level circuit code can represent either electrical extreme

A fuel-level reading that barely changes while fuel is consumed

Low fuel-level sender data received through the tank module

High fuel-level signal on an ECM-connected float circuit

A fuel-level jump that falsely resembles refueling

EGR position differs from the commanded target

A short EGR position excursion differs from a valve stuck open

EGR pressure-sensor performance and its pressure hose

Ford 6.0L exhaust pressure is implausibly high before running

Exhaust pressure offset is compared with ambient pressure after shutdown

Exhaust-pressure low-circuit evidence must retain the source’s labeling caveat

A high exhaust-pressure circuit signal is separate from real overpressure

An erratic exhaust-pressure code can be a model disagreement

exhaust throttle open circuit with an off-state driver

exhaust throttle position-tracking performance

exhaust throttle command short-to-ground detection

exhaust throttle command circuit short to power

exhaust-flap binding can remain after an ECU update

Fan 1 relay-control opening detected with the driver off

Fan relay channel two reports an electrical command mismatch

The third fan relay output has its own feedback check

Fan performance uses weighted command-following evidence

Volkswagen CJAA low-pressure EGR position-sensor circuit

Ford 6.0L EGR throttle actuator circuit fault

Ford throttle open-position learning is outside its limits

high-pressure EGR short-to-ground current signature

exhaust throttle fails its spring-return position check

Volkswagen CJAA exhaust-flap position signal low

Volkswagen CJAA exhaust-flap closed-position learning