See Figure 1
The ABS Control Module (ABS CM) is programmed with a self-diagnostic routine, which constantly monitors the ABS components for problems or erratic behavior. If such a problem or behavior is noted, the control module saves a corresponding Diagnostic Trouble Code (DTC). The DTC, when retrieved, indicates in which component AND circuit the problem lies. Remember that the problem may not be in the component, rather in its circuit. Therefore, it is just as important to inspect the component's circuit as it is to inspect the component itself.
The driver of the vehicle is alerted whenever the ABS CM stores such a DTC: the ABS warning light illuminates during vehicle operation. Normally the warning light should illuminate for approximately 2 seconds when the ignition switch is turned ON , after which the light should turn off. If the light stays on after the 2 seconds, or if during driving, the light illuminates, the ABS CM has detected a problem and stored a DTC.
ABS WARNING LAMP CHECK
See Figure 2
Turn the ignition switch ON and observe the warning light. The light should turn off after 2 seconds. If the light does not turn on at all refer to the accompanying ABS light inspection chart.
READING DIAGNOSTIC TROUBLE CODES (DTC)
ABS Warning Light Method
See Figures 3, 4 and 5
- Locate the DIAG-2 connector, mounted next to the hydraulic unit in the engine compartment.
- Use a jumper wire to connect the diag. switch terminal to ground.
- Turn the ignition switch ON .
- Read and note the flashes of the warning light. Each of the DTC's is composed of two digits, which are represented by the warning light as flashes. Therefore, a code 21 would be comprised of two flashes close together, then one flash after a one second pause. Each code is flashed three times in a row (separated by 3 second pauses), then the control module flashes the next code (if another one is stored).
If the DTC No. 12 is flashed, this indicates that the system is functioning normally. If your warning light indicates that a DTC was stored, there may be a problem with the warning light circuit.
A scan tool can be used to read the DTC's for your ABS system. Follow the scan tool manufacturer's instructions to properly read the DTC's.
CLEARING DIAGNOSTIC TROUBLE CODES (DTC)
- Check the part supply No. on your ABS control module. If the part No. is 33940-77E00, skip to Step 4. If the ABS CM No. is 33940-77E01, proceed to the next step.
- If DTC's 21, 22, 25, 26, 31, 32, 35, or 36 existed prior to repairing the component or circuit, proceed to the next step. Otherwise, skip to Step 4.
- Drive the vehicle between 6.5-12.5 mph (10-20 km/h), then stop the vehicle and turn the ignition switch OFF . The ABS warning light should turn off at this point; if it does not, there are DTC's still stored in the ABS CM, or there is a circuit problem with the warning light. Proceed to the next step, if the warning light turned off.
- If not already done, turn the ignition switch OFF .
- Using a jumper wire, connect the diag. switch terminal of the DIAG-2 connector to the diag. output terminal.
- Turn the ignition switch ON , and leave it ON for at least 10 seconds.
- Perform the DTC reading procedure to ensure that only DTC No. 12 (system normal) is indicated by the ABS warning light.
If you have any continued problems, have the system inspected by a qualified automotive technician with ABS training. The brake system is a very important system to maintain at optimum performance to avoid an accident.