C0870
Adaptive Cruise Control Brake Request Performance
A brake request from adaptive cruise control or AEB cannot be executed within the expected response time.
- Check engine light: Not always
- Emissions related: No
- Repair difficulty: hard
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Common causes
Ordered by how often each turns out to be the cause.
- Bus communication latencyCommon
- Hydraulic block slow to build pressurePossible
Parts involved
- ABS Control Module
- Acc Radar Module
- Communication Bus
C0870 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.