Reading and Clearing Diagnostic Trouble Codes

A bi-directional scan tool connected to the assembly line diagnostic link (ALDL), is needed to access fault codes in the Delco-Moraine anti-lock braking system. Follow manufacturers directions for accessing fault codes. Refer to SCHEMATIC DIAGRAMS/ELECTRICAL AND ELECTRONIC DIAGRAMS for system wiring circuits and DIAGNOSTIC CHARTS for trouble code diagnosis.
The ABS controller, when accessed with a bi-directional scan tool, identifies faults as specifically as possible. This diagnosis will also determine whether or not the fault is intermittent. There are 58 diagnostic fault codes. The first five codes stored, are stored in order of occurrence, from least recent to most recent. Fault codes will not disappear when ignition is turned Off, or when the battery is disconnected. Fault codes can only be read and erased with a bi-directional scan tool. If no faults occur within 50 drive cycles, all fault codes will be cleared. A drive cycle is defined as turning the ignition switch to the On position and vehicle is driven at speeds over 10 mph.
if a fault is detected, which disables the front ABS, the rear anti-lock brakes will continue to operate. The front brakes will have use of the normal power brake system only. If a fault is detected, which disables the rear ABS, the entire ABS will shut down, leaving normal power brake capability only.
Always turn ignition switch to the Off position prior to troubleshooting. This will ensure all diagnostic data is preserved. If ignition switch is not turned to the Off position, any information stored for a fault, in the last drive cycle, will be lost.

NOTE ON INTERMITTENTS

If an intermittent fault cannot be diagnosed using Indicator Lamp Sequence chart, the problem will most probably be caused by a defective electrical connection or wiring. When an intermittent problem is encountered, check questionable circuits and electrical connectors for the following:
1. Poor mating of connector halves or terminals not fully seated in connector body.
2. Improperly formed or damaged terminals. All connector terminals in the problem circuit should be carefully removed to increase contact tension.
3. Poor terminal wire connection.
If a visual check does not locate cause of problem, operate vehicle with EBCM connected and attempt to duplicate condition and use Indicator Lamp Sequence chart to isolate potential cause.