SEAL 1252990 - Caterpillar

System Operation Description:Use this procedure to determine if the auxiliary brake circuit is operating properly. No diagnostic codes are provided for the auxiliary brake output. There may be a problem with the circuit if the operator notes that the vehicle's braking is poor.Background InformationThe Engine Control Module (ECM) has an output that can be configured to activate an auxiliary brake. The "Auxiliary Brake Output" must be programmed to "J1/P1:12" in order to enable the auxiliary brake output. The OEM provides the wiring from terminal P1-12 to the system's components.Typically, the ECM output energizes a relay. The relay's contacts apply battery power to the other components in the system. A switch on the dashboard interrupts the signal from the relay. This allows the operator to deactivate the system, if necessary.The ECM continuously monitors the vehicle's operating conditions. The ECM provides battery voltage to terminal P1-12 when all of the following conditions are met:
Engine speed is above 800 rpm.
The percent of accelerator pedal position is less than eight percent.
The clutch pedal is released.When the cruise control is ON, the auxiliary brake output is related to the position of the service brake pedal. The ECM response depends on the mode of operation of the cruise control:Coast Mode - Depressing the service brake pedal disengages the cruise control. The auxiliary brake output is activated. The output is deactivated when the driver releases the service brake pedal.Latch Mode - Depressing the service brake pedal disengages the cruise control. The auxiliary brake output is activated. The output remains active until the ECM detects a change in the conditions that are monitored. For example, the accelerator pedal is above seven percent.Manual Mode - Depressing the service brake pedal has no effect on the auxiliary brake output.If the "PTO Configuration" is programmed to "Cab Switches", "Remote Switches", or "Remote Throttle", the auxiliary brake output is disabled whenever the PTO On/Off circuit is ON.If the vehicle is equipped with an Anti-Lock Brake System (ABS), the vehicle may have an additional relay in the circuit for the auxiliary brake. This allows the ABS system to disable the auxiliary brake, if necessary.Engines that are equipped with engine retardersThe auxiliary brake output is disabled when the vehicle speed is below the value that is programmed for the "Engine Retarder Minimum Vehicle Speed" parameter. The "Engine Retarder Minimum VSL Type" parameter provides the following two options:Hard Limit (default) - As the vehicle speed decreases, the auxiliary brake output is deactivated when the vehicle speed goes below the "Engine Retarder Minimum Vehicle Speed".Soft Limit - As the vehicle speed decreases, the auxiliary brake output remains activated when the vehicle speed goes below the "Engine Retarder Minimum Vehicle Speed".The "Engine Retarder Delay" parameter provides a programmable delay after all of the basic conditions that are required to turn on the auxiliary brake are met. Once the conditions are met the ECM will delay the activation of the auxiliary brake by the programmed additional time. The programmable range is 0 to 3.0 seconds in