Reading and Clearing Diagnostic Trouble Codes

The EBCM is comprised of two operational subsystems.
- Antilock Brake System (ABS)
- Dynamic Rear Proportioning (DRP)

It performs self-diagnostics on all of its subsystems when the ignition is first turned to ON. When the engine is running and the vehicle is in operation, the EBCM detects and isolates subsystem malfunctions. When a subsystem malfunction is detected, the EBCM sets a corresponding Diagnostic Trouble Code (DTC).
The detection of a malfunction can cause different responses for ABS and DRP. The DRP subsystem requires less functionality of the EBCM to operate properly, so it will be allowed to operate with malfunctions that are disabling to the ABS. This case is referred to as DRP Non-Critical.
In addition to these subsystem responses, the EBCM has special requirements for clearing a Wheel Speed Sensor (WSS) DTC, described below.

Antilock Brake System (ABS) Malfunction Responses
ABS responses to malfunctions fall into four classes:
- Permanent Latched Malfunction Response: This means that the ABS is disabled and the ANTILOCK indicator lamp is requested ON (whenever the ignition is turned ON) even if the cause of the malfunction goes away. This malfunction can not be cleared with a scan tool. The EBCM must be replaced and the module must be returned to the manufacturer.
- Ignition Latched Malfunction Response: This means that the ABS is disabled and the ANTILOCK indicator lamp is requested ON until the ignition is turned OFF even if the cause of the malfunction goes away. When the ignition is turned ON again, the ABS will not be disabled unless/until a subsequent malfunction is detected.
- Condition Latched Malfunction Response: This means that the ABS is disabled and the ANTILOCK indicator lamp is requested ON only as long as the apparent malfunction condition persists. Normal ABS operation resumes automatically and the ANTILOCK indicator is requested OFF as soon as the problem goes away; no service is necessary. The vehicle operator may choose, without being prompted further by the ANTILOCK indicator lamp, to take the vehicle to an authorized service center.
- Information Only Malfunction Response: This means that the ABS is not disabled and no indicator lamp is requested for this malfunction. ABS activity continues as it was before this malfunction occurred.

Dynamic Rear Proportioning (DRP) Malfunction Responses
DRP responses to malfunctions fall into three classes:
- DRP Critical Malfunction Response: This means that the DRP system is disabled and the BRAKE indicator lamp is requested ON. The DRP malfunction is latched the same as the ABS for a given malfunction (Permanent, Ignition, and Condition latched), i.e. a malfunction that is Ignition Latched for ABS activity is also ignition latched for DRP activity.
- DRP Non-Critical Malfunction Response: This means that if more than one of these malfunctions are detected, then DRP is disabled and the BRAKE indicator lamp is requested ON. The DRP malfunction is latched the same as the ABS for a given malfunction (Permanent, Ignition, and Condition latched), i.e. a malfunction that is Ignition Latched for ABS activity is also ignition latched for DRP activity. All DRP non-critical malfunctions are counted separately for purposes of DRP non-critical response, except for sensor malfunctions. All the sensor malfunctions for a particular wheel are counted as a single DRP non-critical malfunction, i.e. a DTC C0221 and C0222 are considered one DRP non-critical malfunction.
- Information Only Malfunction Response: This means that the DRP is not disabled and no indicator lamp is requested for this malfunction. DRP activity continues as it was before this malfunction occurred.

Wheel Speed Sensor (WSS) Malfunction Responses
Because the WSS inputs to the EBCM are of such critical importance to proper system operation, The EBCM requires the following in response to WSS DTCs. If a wheel speed sensor DTC is been set, the ANTILOCK lamp will turn ON to indicate the malfunction. The cause of the DTC must be identified and corrected, the DTC cleared, and the vehicle to have passed the self tests and sensor checks before the ANTILOCK lamp will turn OFF. This means that even after the wheel speed sensor malfunction has been corrected, the ANTILOCK lamp will remain ON until the vehicle is driven above the threshold speed for the EBCM to re-validate the wheel speed sensor inputs. The ANTILOCK lamp will then turn OFF unless or until the next occurrence of an ABS related DTC.