C05A8 code meaning
ABS Pump Motor Supply Voltage B Circuit Range/Performance
What C05A8 means
C05A8 means supply B is present but behaves implausibly: it sags too far once the pump starts, recovers too slowly, or does not match the state the module has commanded. That is different from a hard open (C05A5) or a steady high or low reading (C05A6, C05A7). No maker publishes a threshold for C05A8. Ford's hybrid brake module shows the logic on its single pump feed under C052B: below 6 V with the pump off or below 7.3 V with it on, each for 1.8 s. Mitsubishi lists 10–16 V for the motor feed on the 2023 Outlander PHEV, measured once with the motor switch off and once on. Systems with a second feed, such as the redundant brake-by-wire drive in an Ipgate patent, need this check to know whether the backup path is really usable. Load-test battery and feed.
C05A8 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C05A8
- Intermittent ABS/ESC warning, mostly during pump activity
- Message about reduced braking redundancy on brake-by-wire vehicles
Common causes of C05A8
- Most likelyExcessive voltage drop in the B feed when the pump starts
- PossibleRelay or semiconductor switch in the B path responding slowly or partly
- PossibleAged 12 V battery with high internal resistance
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ABS pump motor supply b
What each part of C05A8 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A8 | The exact fault in that area. |
What to do next
- Note C05A8 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 C05A8
What does C05A8 mean?
C05A8 means "ABS Pump Motor Supply Voltage B Circuit Range/Performance". C05A8 means supply B is present but behaves implausibly: it sags too far once the pump starts, recovers too slowly, or does not match the state the module has commanded. It is a generic code, so it means the same on every make.
Is it safe to drive with C05A8?
Drive gently and only to a workshop. With C05A8 the car can go into limp mode (reduced power) to protect itself.
Will C05A8 fail an emissions test?
C05A8 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 C05A8 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will C05A8 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.