What do P0403 and P0405 together mean?
Quick answer
For Ford’s 2005 model-year diesel application, P0403 identifies an EGR control-circuit fault, while P0405 identifies an EGR position-sensor A circuit-low code. They concern different monitored aspects and do not, by themselves, prove a particular part has failed. These definitions and the P0405 threshold are specific to that application. Provide your year, make, model, engine, code status, and freeze-frame context so a technician can consult the applicable service information. [S1]
The question, the details, the next step.
What do P0403 and P0405 together mean? Does that mean the EGR valve is bad?
For Ford’s 2005 model-year diesel application, P0403 is an EGR control-circuit fault: the monitor flags actuator-driver status indicating an open or short. P0405 is an EGR position-sensor A circuit-low code. The document gives a Ford-specific threshold for P0405, but that threshold is not a general specification for other vehicles. [S1]
The pair therefore describes two different monitored aspects in that application; it does not establish that the EGR valve or another particular part has failed. If your vehicle is not that application, its exact definitions need to be checked against service information for its year, make, model, and engine. [S1]
What details should I collect before asking a shop to check it?
Write down the year, make, model, and engine. Record both codes exactly as displayed, including any status your scan tool shows, and save available freeze-frame information. Note when the warning appeared and any changes you have noticed. This information gives a technician context for checking the correct vehicle-specific definitions and service information. The supplied Ford document does not establish that its definitions or P0405 voltage threshold apply to other vehicles. [S1]
You can use this note:
“Vehicle: [year] [make] [model], [engine]. Codes: P0403 [displayed status], P0405 [displayed status]. Freeze-frame: [available details or not available]. Warning first noticed: [when]. Observed changes: [what you noticed, or none]. Codes cleared: [yes/no/unknown].”
What should I ask the technician to check, without guessing at a failed part?
Ask the technician to interpret both codes for your exact vehicle and explain what evidence supports any proposed repair. For example:
- “What do P0403 and P0405 mean for this year, make, model, and engine?”
- “What do the displayed code status and freeze-frame information show?”
- “What vehicle-specific checks distinguish the EGR control-circuit finding from the low position-sensor signal?”
- “What evidence points to the proposed repair, and how will you confirm the result?”
The source identifies the two monitored aspects for one Ford application; it does not diagnose your vehicle or provide a test procedure. A qualified technician should use the applicable service information for any circuit or component testing. Do not treat the code pair as a reason to bypass or disable emissions equipment. [S1]
If the codes were cleared and have not come back yet, can I call it fixed?
The information available here cannot establish that. The Ford document defines the codes for a specific application, but it does not explain how to interpret a cleared-code situation for your vehicle. Tell the technician that the codes were cleared, when that happened if known, and whether they have returned. Share any saved code details and freeze-frame information, and ask for an assessment based on service information for your exact vehicle. Do not infer a failed part—or a confirmed repair—from the code pair alone. [S1]
A practical checklist
Record the vehicle’s year, make, model, and engine.
Write down both codes and the status displayed by your scan tool.
Save available freeze-frame information and note when the warning appeared.
Record observed changes and whether the codes have been cleared.
Ask for vehicle-specific definitions, diagnostic checks, and evidence supporting any repair.
Have a qualified technician use applicable service information; do not bypass emissions equipment.
A few more useful answers
Does P0405 always mean the position sensor itself has failed?
No. In the Ford 2005 model-year diesel document, P0405 identifies an EGR position-sensor A circuit-low code; that definition does not confirm a failed part or establish the cause for another vehicle. [S1]
Does the Ford document’s 0.30-volt threshold apply to my vehicle?
The document gives that threshold for its Ford 2005 model-year diesel application. It does not establish a threshold for other years, makes, models, or engines. [S1]
Should I replace an EGR component because both codes appeared?
The pair alone does not prove a component has failed. Ask a qualified technician to confirm the definitions for your exact vehicle and explain what evidence supports any proposed repair. [S1]
Sources
References used for this guide.
- [S1] Ford 2005 Model Year Diesel OBD-II System Operation Summary fordservicecontent.com · Checked