In accident reconstruction cases where there is a claimed brake failure, it is often debated whether a full mechanical inspection should be done or just an ACM (Airbag Control Module or “Airbag black box”) imaging of the vehicle. ARCCA recently had the opportunity to investigate a case where performing the full mechanical inspection significantly impacted the outcome.
A driver claimed that his anti-lock brake system (ABS) failed, causing him to lose control of his vehicle during a heavy rain storm. The driver had taken his vehicle to the dealership for service numerous times due to an intermittent ABS light coming on indicating a possible ABS system failure. During these visits the light was ‘off’, and the technician claimed a failure could not be determined. A few days after the last visit, the driver had an accident during the previously mentioned heavy rain storm, causing damage to the vehicle and injury to the driver.
When ARCCA received this case, we reviewed the recalls and technical service bulletins (TSBs) for the vehicle and found a TSB for an issue with the wiring in the wheel speed sensors. During the inspection, a bare wire was found on the left front wheel speed sensor that could cause an intermittent short, just as described in the TSB. This intermittent short would cause a failure of the ABS system. Yes, there was still braking, but no ABS function for the brake system, which would cause diminished stability control due to the wet road conditions.
During the inspection our expert used a scan tool to look into the history section of the diagnostic trouble codes (DTCs) to see if this defect caused a DTC to be set in the past. It revealed that an ABS fault code for the left front wheel speed sensor had occurred numerous times. This is a simple task and should have been performed during the technician’s diagnosis of the claimed ABS light illumination and failure, especially upon a repeated problem as in this case.
ARCCA also imaged the ACM that did have a non-deployment event recorded. There was no indication of an ABS failure or brake failure in the crash data retrieval (CDR) report. However, there was an indication of hydroplaning in the report that would indicate a stability problem occurred as claimed by the driver. In this case, if the CDR report was the only information gathered from the inspection and a further review of the recalls, TSBs and brake system was not performed, it is possible this failure would have been overlooked and the claim deemed to be unfounded or from human error.