C05A4 code meaning
Wheel Speed Sensors Supply Circuit Low
Chassis system Generic code C05xx codes Check engine light
What C05A4 means
The shared feed for the active wheel speed sensors is too low for them to work. In GM's hybrid tables of 2016 and 2019 the brake controller measures, via an internal comparator, the voltage between the sensor supply line and the signal line and sets C05A4 below 6.7 V for 0.06 s while system voltage is above 6.9 V, Type A with MIL; it also blocks the single-wheel codes such as C0500–C0504. A 2019 GM EBCM reads the supply through its ASIC, on units without a regulated sensor feed also against the 12 V input, and sets the code within 15 ms. Allegro's sensor IC needs at least 4 V, or 5.2 V for one variant. On the 2021 Jeep Wrangler 4xe a weak 12 V battery set C05A4 together with other low-voltage codes and a MIL; the fix was to charge, test and replace the battery (08-106-21). Check battery and charging before parts.
C05A4 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C05A4
- ABS, traction and stability control lamps on, MIL possible
- Several wheel speed codes at once, often with low-voltage codes
- Hard starting or no start when the 12 V battery is the cause
Common causes of C05A4
- Most likelyDischarged or failing 12 V battery (FCA 08-106-21)
- PossibleWheel speed sensor wiring shorted to ground, pulling the shared supply down
- Less likelySensor supply stage inside the brake module failing
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Wss supplyWheel speed sensorABS control module
What each part of C05A4 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A4 | The exact fault in that area. |
What to do next
- Note C05A4 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 C05A4
What does C05A4 mean?
C05A4 means "Wheel Speed Sensors Supply Circuit Low". The shared feed for the active wheel speed sensors is too low for them to work. It is a generic code, so it means the same on every make.
Is it safe to drive with C05A4?
Drive gently and only to a workshop. With C05A4 the car can go into limp mode (reduced power) to protect itself.
Will C05A4 fail an emissions test?
C05A4 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 C05A4 to fix?
Difficulty: medium. A typical repair takes 0.3 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will C05A4 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.