OBD-II trouble code
U045B: Invalid Data Received From Anti-Lock Brake System (ABS) Control Module B
A module is receiving messages from a second ABS control module ('B'), but the data — wheel speeds or brake status — is implausible or out of range. The link is alive; the content is wrong. Base braking still works, but ABS and stability control may switch off.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $90 – $1,200
- DIY difficulty
- Advanced DIY
What does U045B mean?
U045B means a module is still receiving messages from the anti-lock brake system (ABS) control module 'B', but the data in those messages is invalid — out of range, implausible, or in conflict with other information. The 'B' designation identifies a second ABS/brake controller on vehicles that split braking control across more than one module — for example some heavy-duty, dual-circuit, all-wheel-drive, or trailer-equipped platforms, and certain vehicles that separate front and rear brake control. This is not a lost-communication fault; module 'B' is talking, but what it reports doesn't make sense, so the receiving module rejects the data and stores U045B. That is the defining difference from U015A, the lost-communication version, where the module goes completely silent.
Because the problem is bad content rather than a dead link, the causes center on whatever makes the ABS module send implausible values. A failing or out-of-range wheel speed sensor is one of the most common reasons — a damaged sensor, a contaminated or damaged tone ring, excessive wheel bearing play, or wiring problems can make one wheel's reported speed implausible relative to the others. The module's calibration or internal circuitry can be at fault, particularly after it was replaced or a tire, wheel, or axle change altered the expected signal. Low system voltage can push modules to report implausible data, and electrical noise or marginal bus wiring can corrupt otherwise-valid messages. There are usually companion ABS codes naming the specific wheel or signal at fault, and those should be read first.
Symptoms typically include the ABS, stability control (ESC/ESP), and traction control warning lights, since those systems disable themselves when they can't trust the wheel speed data — and the speedometer can behave oddly if it relies on that data. Base braking still works: you keep normal hydraulic brakes, just without ABS and stability assistance. The vehicle remains driveable, but driving without those safety features, especially in rain, snow, or on loose surfaces, is a good reason to diagnose U045B promptly rather than ignore it.
Common causes
- Failing or out-of-range wheel speed sensor feeding implausible data
- Damaged or contaminated tone/reluctor ring, or excessive wheel bearing play
- Low system voltage, a weak battery, or a poor ground at the module
- Corroded, loose, or damaged connectors at the ABS module or sensors
- Chafed or damaged bus wiring corrupting messages in transit
- ABS module 'B' replaced without correct configuration or calibration
- Outdated, corrupted, or mismatched module software
- Internal ABS control module 'B' fault
Symptoms
- ABS warning light on
- Stability control (ESC/ESP) and traction control lights on or disabled
- Speedometer occasionally erratic if it relies on wheel speed data
- Companion wheel speed sensor or ABS codes stored alongside U045B
- Normal hydraulic braking retained, but no ABS/stability assist
Diagnostic steps
- 1.Read all stored codes and address any wheel-specific ABS or wheel speed sensor codes first — they usually name the fault.
- 2.Load-test the battery and verify charging voltage and the module's grounds.
- 3.Inspect the wheel speed sensors, tone rings, and their wiring for damage, contamination, and corrosion.
- 4.Check for excessive wheel bearing play that can distort the wheel speed signal.
- 5.Confirm whether the ABS module, a sensor, or a wheel/axle component was recently serviced — a missing configuration is a common cause.
- 6.Inspect bus wiring and connectors to the module for chafing, corrosion, and bent pins.
- 7.If inputs and wiring check out, suspect an internal module fault and verify with manufacturer service data.
Repair cost
$90 – $1,200
Cost depends on the cause. A wheel speed sensor is often $150-$400 installed. Repairing a connector, ground, or wiring fault is typically $90-$400. Reprogramming or configuring the module after a replacement is usually $100-$300. ABS control module replacement with programming is the higher end at roughly $500-$1,200 depending on the vehicle. Confirm a sensor, wiring, or software fix before replacing the module.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with module communication / can bus diagnosis preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an advanced DIY job. It typically requires specialty tools, scan-tool access, lifting equipment, or careful sequencing to avoid causing new failures. Plan for extended downtime and have a backup vehicle. Most owners are better served by a shop that has done this repair before.