ABS voltage · Chassis code
ABS low or abnormal voltage codes
The anti-lock brake module measured its supply voltage and found it too low, too high, or unstable. The ABS module is usually reporting a problem elsewhere — most often the battery, charging system or a ground connection.
What this code means
The ABS module has a powerful pump motor and valves, and it needs steady voltage to run its self-checks and operate safely. It constantly monitors the supply it's getting.
C0564 means the module saw its system voltage drop below its acceptable range; C0565 means voltage went above it. U3003 is a general battery voltage fault that ABS and other modules can store. You'll often find similar voltage codes stored in several modules at once — a strong sign the problem is the car's electrical supply, not the brake system.
Low-voltage codes commonly appear after a jump start, a battery that's been run flat, or during long cranking on a weak battery. High-voltage codes usually point to an alternator that's overcharging.
Symptoms you may notice
- ABS, traction control or brake warning lights, sometimes several dash lights at once
- Slow cranking or a no-start
- Dim or flickering headlights
- Battery or charging warning light
- Warning lights that come and go with engine speed or electrical load
Common causes, most likely first
- Weak or failing batteryThe most common cause, especially if the battery is more than 3–5 years old or has been drained.
- Loose or corroded battery terminalsPoor connections cause voltage drops under load, which the ABS pump puts a lot of.
- Failing alternator or voltage regulatorUndercharging sets low-voltage codes; overcharging sets high-voltage codes.
- Bad ground connectionA corroded or loose ground strap near the ABS module or between the engine and body.
- Damaged ABS power feed, fuse or connectorLess common; often after a collision or water intrusion near the module.
What to check first
- Have the battery load-tested and the charging system checked. Most parts stores do this for free. With the engine running, charging voltage should typically sit around 13.5–14.7 volts.
- Clean and tighten both battery terminals, and inspect the main ground straps.
- Check whether other modules have stored voltage codes too. If so, focus on the electrical supply rather than the ABS.
- If the code appeared right after a jump start or battery replacement, clear it and see whether it returns.
- If the battery and charging system test fine, a shop can check voltage at the ABS module connector and its fuses and grounds.
Typical repairs and rough cost
| Repair | Typical cost | Notes |
|---|---|---|
| Battery replacement | $150–$350 | AGM batteries on start-stop vehicles cost more, and some need registering with a scan tool. |
| Terminal or ground cleaning/repair | $0–$150 | Often a do-it-yourself fix. |
| Alternator replacement | $400–$900 | |
| ABS power feed or connector repair | $100–$400 | Rarely the ABS module itself. |
Rough US shop prices for parts and labor. Your cost depends on the vehicle, the parts brand and local labor rates.
Official code definitions
| Code | Applies to | Definition |
|---|---|---|
| C0564 | Generic | ABS Control Module System Voltage Low |
| C0565 | Generic | ABS Control Module System Voltage High |
| U3003 | Generic | Battery Voltage |
“Generic” codes mean the same thing on every make. Manufacturer entries are that brand’s own description. Look up any other code in the code library.
Common questions
Do I need a new ABS module?
Rarely. Voltage codes in the ABS module almost always trace back to the battery, alternator or a connection. Rule those out first; ABS modules are expensive.
Why did my ABS light come on after a jump start?
Voltage drops and spikes during a jump or a long crank can set low-voltage codes. If the battery and charging system test fine, clearing the code often fixes it.
Can a bad alternator cause ABS problems?
Yes. An alternator that undercharges sets low-voltage codes, and one that overcharges sets high-voltage codes, in the ABS module and others.
Related codes
This guide explains what the code usually means and how it’s typically diagnosed. Every car is different, and a code points to a system, not always a specific part. For anything affecting brakes, steering or a car that feels unsafe, have a qualified mechanic confirm before you rely on it.