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.

NH3 Sensor Supply Voltage Circuit Low

NH3 Sensor Supply Voltage Circuit High

NH3 Sensor Calibration Memory

NH3 Sensor Processor Performance

Control-module wake-up output is open in its off state

Wake-up output voltage is low during an on command

Wake-up circuit remains high with the command off

EGR Temperature/Charge Air Cooler Temperature Correlation

Reductant Tank Temperature/Fuel Temperature Correlation

NOx Sensor Delayed Response - High to Low Bank 1 Sensor 1

NOx Sensor Delayed Response - High to Low Bank 1 Sensor 2

Exhaust Aftertreatment Fuel Air Purge Valve Stuck Open

Exhaust Aftertreatment Fuel Air Purge Valve Stuck Closed

Exhaust Aftertreatment Fuel Air Purge Valve Control Circuit

Exhaust Aftertreatment Fuel Air Purge Valve Control Circuit Range/Performance

Exhaust Aftertreatment Fuel Air Purge Valve Control Circuit Low

Exhaust Aftertreatment Fuel Air Purge Valve Control Circuit High

Particulate Matter Sensor Heater Control Circuit Driver Current/Temperature Too High

Particulate Filter A Incorrect

An incorrect SCR catalyst code uses cumulative conversion evidence

Reductant Temperature Too High

Generator Lamp/L-Terminal Circuit Low

Generator Lamp/L-Terminal Circuit High

Charging-system voltage fault with several hybrid battery triggers

Low voltage at a Mazda M Hybrid charging-system node

High voltage across the hybrid charging network

Interrupted permanent ECM supply affects engine-off timing

ECM/PCM Power Input Signal Range/Performance

Mazda transport-mode starts can leave a low-voltage history code

Ford internal ECU five-volt supply is too high

ECM/PCM Power Input Signal Intermittent

Oil-level sensor errors can also result from excessive oil

Engine Oil Level Sensor Circuit Range/Performance

Hyundai oil-level circuit-low warning and ROM matching

Engine Oil Level Sensor Circuit High

Engine Oil Level Sensor Circuit Intermittent/Erratic

Venue oil-level warning: the dipstick decides the branch

ECM relay faults can mean power ends too late or too early

ECM/PCM Power Relay Sense Circuit Intermittent

Event Data Recorder Request Circuit/ Open

Event Data Recorder Request Circuit Low

Event Data Recorder Request Circuit High

A/C Refrigerant Pressure Sensor B Circuit

Low-side refrigerant pressure must respond after compressor start

Low-side refrigerant sensor voltage is below its valid range

High refrigerant sensor voltage has its own sample and trip logic

A/C Request A Circuit

PTO Enable Switch Circuit/Open

PTO Enable Switch Circuit Low

PTO Enable Switch Circuit High

PTO Engine Shutdown Circuit/Open

PTO Engine Shutdown Circuit Low

PTO Engine Shutdown Circuit High

A/C Request A Circuit Low

A/C Request A Circuit High

A/C Request B Circuit

A/C Request B Circuit Low

A/C Request B Circuit High

Vacuum Reservoir Pressure Sensor Circuit

Vacuum Reservoir Pressure Sensor Circuit Range/Performance

Vacuum Reservoir Pressure Sensor Circuit Low

Vacuum Reservoir Pressure Sensor Circuit High

Vacuum Reservoir Pressure Sensor Circuit Intermittent

The DME loses communication with the oil-condition sensor

Engine Oil Quality Sensor Circuit Range/Performance

Engine Oil Quality Sensor Circuit Low

Engine Oil Quality Sensor Circuit High

Engine Oil Quality Sensor Circuit Intermittent/Erratic

Diesel oil level too high, dilution and reset history

Mazda CX-50 Hybrid startup failure and campaign eligibility

Ignition Switch Run Position Circuit Low

Ignition Switch Run Position Circuit High

Why an ignition-state fault can appear in throttle supervision

Transmission controller sees run/crank low while the ECM reports it active

Run/start input stays high after the reported run/crank state becomes inactive

Transmission controller sees accessory input disagree with power mode

Accessory-line voltage disagrees with the wakeup state

accessory-input diagnosis includes the network power-mode state

Transit KOEO self-test code versus a running-engine fault

PTO Sense Circuit/Open