C05A8ABS Pump Motor Supply Voltage B Circuit Range/Performance
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Intermittent ABS/ESC warning, mostly during pump activity
- Message about reduced braking redundancy on brake-by-wire vehicles
- Likely causes
- 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
- Repair
- Medium · Usually a job for a workshop.Typical cost: €0 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.