Chassis, generic

C05A4 Wheel Speed Sensors Supply Circuit Low

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Discharged or failing 12 V battery (FCA 08-106-21)
Wheel speed sensor wiring shorted to ground, pulling the shared supply down
Sensor supply stage inside the brake module failing

Symptoms

  • 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

Repair estimate

DifficultyMediumDIY possible
Parts and labour€0–900
Time0.3–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

wss supplywheel speed sensorabs control module

Related codes

C05A3C0500C0502C0564P0562

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov, allegromicro.com.