OBD2 Car ScannerWhat does P04A4 mean?
P04A4 stands for Exhaust Pressure Control Valve B Stuck Open. A part of the emission control system is not working as expected. These codes rarely affect how the car drives, but the car may fail an emissions test.
Powertrain codes cover the engine, transmission and emissions. When the car's computer sees a reading outside its normal range, it stores this code and may turn on a warning light on the dashboard.
Common causes
- Loose or damaged fuel cap (EVAP codes)
- Worn catalytic converter
- Faulty EGR valve or blocked EGR passages
- Faulty oxygen sensor
- Cracked hoses or a leaking purge valve
What to do
- Read all stored and pending codes with a scanner. Several codes together often point to one cause.
- Note the freeze frame data (speed, temperature, load) recorded when the code was set.
- Inspect the wiring and connectors of the part named in the code for damage, corrosion or looseness.
- Fix the most likely and cheapest cause first, then clear the code and drive to see if it comes back.
Read this code from your own car
Plug in a cheap ELM327 adapter and the app shows every fault code, what it means and how to fix it.
Frequently asked questions
What does P04A4 mean?
P04A4 means “Exhaust Pressure Control Valve B Stuck Open”. It belongs to the emission controls group: A part of the emission control system is not working as expected. These codes rarely affect how the car drives, but the car may fail an emissions test.
Is it safe to drive with P04A4?
Usually yes in the short term, but get it fixed so the car passes inspection and doesn't waste fuel.
How do I clear P04A4?
Fix the cause, then clear the code with an OBD2 scanner or app. If the fault is still there, the code will come back.
Related codes
- P04A0Exhaust Pressure Control Valve B Range/Performance
- P04A1Exhaust Pressure Control Valve B Low
- P04A2Exhaust Pressure Control Valve B High
- P04A3Exhaust Pressure Control Valve B Intermittent
- P04A5Exhaust Pressure Control Valve B Stuck Closed
- P04A6Exhaust Pressure Control Valve B Position Sensor/Switch Circuit
- P04A7Exhaust Pressure Control Valve B Position Sensor/Switch Circuit Range/Performance
- P04A8Exhaust Pressure Control Valve B Position Sensor/Switch Circuit Low
Code meanings can vary by manufacturer. This page is general guidance, not a repair manual. Always confirm the cause before replacing parts.