P04CA: Fuel Fill Door Open Request Sensor or Switch Circuit Low
Same as P04C8 with the signal voltage shorted to ground or constantly low. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
What P04CA means
P04CA is a generic OBD-II powertrain code in the fuel & air group. In plain English: the computer sees a voltage on that circuit that is lower than it should ever be — often a short to ground, an open, or a failed sensor.
- Check engine light
- Usually off
- Emissions-related
- No
- Limp mode possible
- Not typical
- Drive cycle to clear
- Not required
Get it fixed
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Common causes
- 01Signal shorted to groundMost likely
- 02Connector pins corroded - high contact resistanceLess likely
- 03Harness chafing through insulationLess likely
Can I drive with P04CA?
Generally yes.
This fault is unlikely to affect how the car drives. Fix it when convenient.
Why we rate it low
- Does not normally turn on the check engine light
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose P04CA
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P04CA. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Fix other faults first
If other codes are stored, start with power-supply, sensor-circuit and communication codes. They can cause this code as a side effect.
- 3
Test the circuit
Inspect the wiring and connector at the fuel fill door request switch for damage, corrosion or chafing. With a multimeter, check supply voltage, ground and signal against the specifications in the service manual for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Signal shorted to ground; connector pins corroded - high contact resistance; harness chafing through insulation. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
P04CA repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Easy
- Good DIY job?
- Yes, with a scan tool
Basic hand tools; a common first DIY job.
Parts and systems involved
- Fuel fill door request switch
P04CA FAQ
What does P04CA mean?
P04CA means “Fuel Fill Door Open Request Sensor or Switch Circuit Low”. Same as P04C8 with the signal voltage shorted to ground or constantly low. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
Is P04CA serious? Can I keep driving?
We rate P04CA as low severity. Generally yes. This fault is unlikely to affect how the car drives. Fix it when convenient.
What causes P04CA?
The most common causes, from most to least likely: Signal shorted to ground; Connector pins corroded - high contact resistance; Harness chafing through insulation. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P04CA?
Typical labor is about $50–$125 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix P04CA myself?
DIY difficulty is easy. Many owners can handle it with a scan tool, a multimeter and basic hand tools. Always confirm the cause before buying parts.
Will P04CA clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.