C15 – Engine Retarder (Compression Brake) Will Not Turn ON

Probable Causes

The probable root causes are listed in order below:
• Customer Specified Parameter (Engine Retarder)

• Cruise Control On/Off Switch
• Engine Retarder On/Off Switch
• Retarder Off/Low/Medium/High Switch
• Accelerator Pedal Position Sensor
• Clutch Switch
• Additional Customer Specified Parameters
• PTO On/Off Switch

Recommended Actions

Perform the following diagnostic procedures in order:
1. Check the Engine Retarder Mode.
If the Engine Retarder Mode is programmed to Latch or Coast, the engine retarder will not activate unless the service brake pedal is depressed.
If the Engine Retarder Mode is programmed to Manual, service brakes are not required.

2. Check the Engine Retarder On/Off Switch and the Retarder Off/Low/Medium/High Switch.
Note: The Engine Retarder On/Off Switch must be in the ON position in order to permit engine retarder operation.
a. Connect an Electronic Service Tool to the Cab Data Link Connector.
b. Turn the ignition key to the ON position while the engine is OFF.
c. Access the status screen for the Engine Retarder Switch.
d. Move the engine retarder switches to each of the available levels while the status of the switch is being watched on the Electronic Service Tool. The available levels of the engine retarder switches have the following designations:
• Off
• Low
• Medium
• High

Note: Some vehicles may have a set of switches on the dash and the shift lever.

If the status for the Engine Retarder Switches does not correspond to the position of the Engine Retarder Switches, refer to Troubleshooting, “Retarder (Compression Brake) Solenoid circuit – Test”.

3. Check the Accelerator Pedal Position Sensor and the Clutch Switch.
a. Connect an Electronic Service Tool to the Cab Data Link Connector.
b. Turn the ignition key to the ON position while the engine is OFF.
c. Access the status screen for the Accelerator Pedal Position.
d. Depress the accelerator pedal and release the accelerator pedal several times while the status screen for the accelerator pedal is being watched.

The Accelerator Pedal Position should be in a range of 3 to 100 percent. If the Accelerator Pedal Position is not in a range of 3 to 100 percent, refer to Troubleshooting, “Accelerator Pedal (Throttle) Position Sensor Circuit – Test”.

e. Access the status screen for the Clutch Switch.
f. Depress the clutch pedal and release the clutch pedal several times while the status screen for the Clutch Switch is being watched.

The status screen for the Clutch Switch should indicate that the clutch pedal is being
depressed and released. When the clutch pedal is being depressed the status screen
should indicate ON. When the clutch pedal is being released the status screen should
indicate OFF. If the status of the Clutch Switch does not correspond to the position of the clutch pedal, refer to Troubleshooting, “Accelerator Pedal (Throttle) Position Sensor Circuit – Test”.

4. Check additional Customer Specified Parameters.
a. Connect an Electronic Service Tool to the Cab Data Link Connector.
b. Turn the ignition key to the ON position while the engine is OFF.
c. Access the Customer Specified Parameters screen.
d. Review the programming of the following parameters:

• “Engine Retarder Minimum Vehicle Speed”
• “Engine Retarder Minimum Vehicle Speed Type”
• “Engine Retarder Delay”

“Engine Retarder Minimum Vehicle Speed” – The engine retarder will not turn ON below
the programmed value when the programmed value is greater than 0 km/h (0 mph).

“Engine Retarder Minimum Vehicle Speed Type” – When vehicle speed drops below the Engine Retarder Minimum Vehicle Speed and this parameter is programmed to Hard Limit the engine retarder turns OFF. When vehicle speed drops below the Engine Retarder Minimum Vehicle Speed and this parameter is programmed to Soft Limit the engine retarder remains ON.

“Engine Retarder Delay” – This parameter provides a programmable delay after the
conditions that turn ON the Engine Retarder are met.

If the problem is due to the programming of any of the listed parameters, refer to
Troubleshooting, “Customer Specified Parameters”.

5. Check the PTO On/Off Switch.
Note: If the “PTO Configuration” (Customer Specified Parameter) is programmed to Cab Switches, Remote Switches or Remote Throttle, the Engine Retarder is disabled when the PTO On/Off
circuit is in the ON position.

a. Connect an Electronic Service Tool to the Cab Data Link Connector.
b. Turn the ignition key to the ON position while the engine is OFF.
c. Access the status screen for the PTO On/Off Switch.

If the status of the PTO On/Off Switch does not correspond to the position of the PTO
On/Off Switch, refer to Troubleshooting, “PTO Switch Circuit – Test”.

 

Leave a Reply

Your email address will not be published. Required fields are marked *