C0504 code meaning
Left Front Wheel Speed Sensor A Intermittent/Erratic
Chassis system Generic code C05xx codes Check engine light
What C0504 means
C0504 points to a left front speed signal that jumps or produces far too many edges, not one that is missing. GM's 2016 hybrid brake module stores a time stamp for every sensor edge in a buffer and sets C0504 within 0.03 s when that buffer overflows; the 2023 tables apply the same idea to a DMA transfer unit receiving time stamps too often. For 2020 Chevrolet Silverado and GMC Sierra 2500/3500HD, GM preliminary information PIT5707 ties C0504 and its right-hand twin C050A to manufacturing debris on the reluctor ring: clean it without using a magnet, which may mean removing the hub bearing. Mitsubishi (C1061-38) checks the signal between 10 and 60 km/h, needs two trips for the MIL and lists the sensor rotor among the causes.
C0504 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of C0504
- ABS lamp and service stability message on the driver display
- Fault comes and goes with road surface or steering angle
Common causes of C0504
- Most likelyMetal debris or dirt on the reluctor ring (GM PIT5707)
- PossibleLoose contact in the sensor plug or a wire breaking under movement
- PossibleDamaged tone ring or encoder
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Wss lfTone ring lfSensor wiring
What each part of C0504 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 04 | The exact fault in that area. |
What to do next
- Note C0504 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C0504
What does C0504 mean?
C0504 means "Left Front Wheel Speed Sensor A Intermittent/Erratic". C0504 points to a left front speed signal that jumps or produces far too many edges, not one that is missing. It is a generic code, so it means the same on every make.
Is it safe to drive with C0504?
Drive gently and only to a workshop. With C0504 the car can go into limp mode (reduced power) to protect itself.
Will C0504 fail an emissions test?
C0504 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C0504 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will C0504 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.