C13 and C15 Engines for Combat and Tactical Vehicles Caterpillar


Retarder (Compression Brake) Solenoid Circuit - Test

Usage:

C13 EMS
System Operation Description:

Use this procedure to troubleshoot any suspect problems with the circuits for the engine retarder solenoids.

This procedure covers the following diagnostic codes:

  • 121-05 Low/High Retarder current low

  • 121-06 Low/High Retarder current high

  • 122-05 Med/High Retarder current low

  • 122-06 Med/High Retarder current high

The engine retarder solenoids are usually factory installed at Caterpillar and the switches are installed by the vehicle OEM. The Engine Control Module (ECM) directly drives the retarder solenoids, eliminating OEM installed relays and circuit protection. The ECM reads the status of the OEM installed engine retarder switches in order to determine the following modes of operation:

  • OFF

  • Low

  • Medium

  • High

Operation of the retarder solenoids is inhibited during undesirable engine operating conditions.

All of the following conditions must be met in order to ensure the proper retarder operation regardless of the settings of the customer specified parameters:

  • Engine speed is above 800 rpm.

  • The "Accelerator Pedal Position" is less than eight percent.

  • The clutch pedal is released.

Additional factors may affect retarder operation. The additional factors are based on the programming of certain customer specified parameters. Refer to Troubleshooting, "Customer Specified Parameters" for more information. The following parameters may affect retarder operation:

  • "Engine Retarder Mode"

  • "Auto Retarder In Cruise"

  • "Auto Retarder In Cruise Increment"

  • "Engine Retarder Minimum Vehicle Speed"

  • "Engine Retarder Minimum Vehicle Speed Type"

  • "Engine Retarder Delay"

Note: If the "PTO Configuration" is programmed to "Cab Switches", to "Remote Switches", or to "Remote Throttle", the engine retarder is disabled whenever the PTO On/Off circuit is On.

Trucks that are equipped with SAE J1939 systems may also control the engine retarder. For an Anti-Lock Brake System (ABS) that does not use SAE J1939 with the engine retarder solenoids, a relay may be connected into the retarder switch circuit in order to disable the engine retarder or a relay may be connected into the clutch switch circuit in order to disable the engine retarder.

Note: If the vehicle is equipped with an ABS, the vehicle may have an additional relay in the switch circuit for the engine retarder switches or the clutch switch. This is installed so the ABS can turn off the engine retarder, if necessary. The relay should have normally closed contacts. The ABS cannot turn on the engine retarder. The Caterpillar ECM must still activate the retarder.

Note: If the "Transmission Style" parameter is programmed to "Eaton Top 2", normal engine retarder operation can be inhibited by the ECM. Normal engine retarder operation can be inhibited by the ECM when the driver is attempting to make a shift in Top 2 mode in order to provide better control of torque during the process of shifting.

"Retarder Brake Test"

The "Retarder Brake Test" is a diagnostic test that is available on the Caterpillar Electronic Technician (ET). Use the "Retarder Brake Test" to assist in troubleshooting problems in the circuit for the engine retarder. The ECM will only detect shorts in the circuit for the engine retarder when the test is active. "Current high" diagnostic codes (short circuits) will be logged once the test has been deactivated. The ECM will only detect opens in the circuit for the engine retarder when the test is not active. The test must be activated and then deactivated before the ECM will detect an open circuit. "Current low" diagnostic codes (open circuits) will be active once the test has been deactivated.

The following conditions must be met before the "Retarder Brake Test" will function:

  • Engine speed is 0.

  • Vehicle speed is 0.

  • The neutral switch is in the Neutral position.


Illustration 1g01100303
Schematic for C15 engine retarder

Note: For C13 engines for Combat and Tactical Vehicles, refer to Schematic, KENR9594.



Illustration 2g01100305
P1 ECM connector
(P1-5) "AP Sensor/Switch Sensor Common"
(P1-23) "Retarder Solenoid LOW/HI Switch"
(P1-40) "Retarder Solenoid MED/HI Switch"


Illustration 3g01100308
P2 ECM connector
(P2-1) "Retarder solenoid LOW/HI"
(P2-8) "Retarder solenoid MED/HI"
(P2-14) "Retarder solenoid common"


Illustration 4g01100311
Valve cover connectors for C15 engines
(1) Terminal 12 Retarder solenoid common
(2) Terminal 11 Retarder solenoid LOW/HI
(3) Terminal 10 Retarder solenoid MED/HI
(4) Terminal 1 Retarder solenoid MED/HI
(5) Terminal 2 Retarder solenoid common

Test Step 1. Inspect Electrical Connectors and Wiring

  1. Thoroughly inspect the J1/P1 and J2/P2 ECM connectors, the valve cover connectors and the firewall bulkhead connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

  2. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the connections for the engine retarder solenoids and for the engine retarder switch:

  3. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

  4. Check the harness and wiring for abrasion and for pinch points from the accelerator pedal position sensor to the ECM.

Expected Result:

All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion or of pinch points.

Results:

  • OK - The harness and wiring are OK. Proceed to Test Step 2.

  • Not OK - There is a problem in the connectors and/or wiring.

    Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.

    Verify that the repair eliminates the problem.

    STOP

Test Step 2. Check for Active Diagnostic Codes and/or Logged Diagnostic Codes

  1. Connect Cat ET to the service tool connector.

  2. Turn the key switch to the ON position.

  3. Access the "Special Tests" under the "Diagnostics" menu.

  4. Start the "Retarder Brake Test" on Cat ET.

  5. Once Cat ET displays the status of the engine retarder solenoid, stop the "Retarder Brake Test".

  6. Check for active diagnostic codes and/or logged diagnostic codes that are associated with the retarder solenoids.

Expected Result:

No diagnostic codes are active.

Results:

  • OK - No diagnostic codes are active. If a problem is suspected with the "Engine Retarder Solenoid Selector Switch", proceed to Test Step 9.

  • Not OK - A low current diagnostic code (05) is active at this time. Proceed to Test Step 3.

  • Not OK - A high current diagnostic code (06) is logged at this time. Proceed to Test Step 5.

Test Step 3. Short the Wires of the Suspect Engine Retarder Solenoid at the Valve Cover Connector

  1. Turn the key switch to the OFF position.

  2. Disconnect the valve cover connector for the suspect engine retarder solenoid.

  3. Fabricate a jumper wire in order to create a short between the supply and the return for the suspect engine retarder solenoid.

  4. Turn the key switch to the ON position.

  5. Access the "Special Tests" under the "Diagnostics" menu.

  6. Start the "Retarder Brake Test" on Cat ET.

  7. Once Cat ET displays the status of the engine retarder solenoid, stop the "Retarder Brake Test".

  8. Check for active diagnostic codes and/or logged diagnostic codes that are associated with the retarder solenoids.

Expected Result:

A high current diagnostic code (06) is logged at this time.

Results:

  • OK - A high current diagnostic code (06) is logged at this time. The harness wiring between the valve cover connector for the suspect engine retarder solenoid and ECM connector P2 is OK. Proceed to Test Step 7.

  • Not OK - A low current diagnostic code 05 is active at this time. The ECM did not see the short at the valve cover connector for the engine retarder solenoid. Proceed to Test Step 4.

Test Step 4. Create a Short Circuit at the ECM

  1. Turn the key switch to the OFF position.

  2. Disconnect the J2/P2 ECM connector.

  3. Inspect the terminals on the J2 and P2 ECM connectors for damage.

    Note: Refer to the Figure 3 for pin locations.

  4. Remove the return wire and the supply wire for the suspect engine retarder solenoid from the P2 ECM connector.

  5. Fabricate a jumper wire in order to short the two pins for the suspect engine retarder solenoid at the ECM. Crimp a socket to each end of the jumper wire. Insert the jumper wire into the P2 ECM connector.

  6. Reconnect the P2 ECM connector.

  7. Turn the key switch to the ON position.

  8. Access the "Special Tests" under the "Diagnostics" menu.

  9. Start the "Retarder Brake Test" on Cat ET.

  10. Once Cat ET displays the status of the engine retarder solenoid, stop the "Retarder Brake Test".

  11. Check for active diagnostic codes and/or logged diagnostic codes that are associated with the retarder solenoids.

Expected Result:

A high current diagnostic code (06) is logged at this time.

Note: Disconnecting the supply wire for the suspect engine retarder solenoid will cause an "Open" in the engine retarder solenoid that shares the supply wire with the suspect engine retarder solenoid.

Results:

  • OK - A high current diagnostic code (06) is logged at this time. The ECM recognized the short.

    Repair: Check continuity of the supply wire for the suspect engine retarder solenoid between the valve cover connector for the suspect engine retarder solenoid and P2. If the wire is open, replace the wire.

    Check continuity of the return wire for the suspect engine retarder solenoid between the valve cover connector for the suspect engine retarder solenoid and P2. If the wire is open, replace the wire.

    STOP

  • Not OK - A low current diagnostic code 05 is active at this time. The ECM did not recognize the short circuit.

    Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

    Verify that the repair eliminates the problem.

    STOP

Test Step 5. Open the Wires of the Suspect Engine Retarder Solenoid at the Valve Cover Connector

  1. Turn the key switch to the OFF position.

  2. Disconnect the valve cover connector for the suspect engine retarder solenoid.

  3. Turn the key switch to the ON position.

  4. Access the "Special Tests" under the "Diagnostics" menu.

  5. Start the "Retarder Brake Test" on Cat ET.

  6. Once Cat ET displays the status of the engine retarder solenoid, stop the "Retarder Brake Test".

  7. Check for active diagnostic codes and/or logged diagnostic codes that are associated with the retarder solenoids.

Expected Result:

A low current diagnostic code (05) is active at this time.

Results:

  • OK - A low current diagnostic code (05) is active at this time. The ECM recognized the open at the valve cover connector for the engine retarder solenoid. The harness wiring between the valve cover connector for the suspect engine retarder solenoid and ECM connector P2 is OK. Proceed to Test Step 8.

  • Not OK - A high current diagnostic code (06) is logged at this time. The ECM did not see the open at the valve cover connector for the engine retarder solenoid. Proceed to Test Step 6.

Test Step 6. Create an Open at the ECM

  1. Turn the key switch to the OFF position.

  2. Disconnect the P2 ECM connector.

  3. Inspect the terminals on the J2 and P2 ECM connectors for damage.

    Note: Refer to the Figure 3 for pin locations.

  4. Remove the return wire and the supply wire for the suspect engine retarder solenoid from the P2 ECM connector.

  5. Reconnect the P2 ECM connector.

  6. Turn the key switch to the ON position.

  7. Access the "Special Tests" under the "Diagnostics" menu.

  8. Start the "Retarder Brake Test" on Cat ET.

  9. Once Cat ET displays the status of the engine retarder solenoid, stop the "Retarder Brake Test".

  10. Check for active diagnostic codes and/or logged diagnostic codes that are associated with the retarder solenoids.

Expected Result:

A low current diagnostic code (05) is active at this time.

Results:

  • OK - A low current diagnostic code (05) is active at this time. The ECM recognized the open at the ECM.

    Repair: Disconnect the P2 ECM connector. Measure the resistance between the supply wire for the suspect engine retarder solenoid and every terminal on ECM connector P1 and ECM connector P2. Measure the resistance between the supply wire for the suspect engine retarder solenoid and engine ground. If the wire is shorted, replace the wire.

    Measure the resistance between the return wire for the suspect engine retarder solenoid and every terminal on ECM connector P1 and ECM connector P2. If the wire is shorted, replace the wire.

    STOP

  • Not OK - A high current diagnostic code (06) is logged at this time. The ECM did not recognize the open.

    Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

    STOP

Test Step 7. Create a Short Circuit at the Engine Retarder Solenoid

  1. Turn the key switch to the OFF position.

  2. Reconnect the valve cover connector.

  3. Remove the valve cover.

  4. Disconnect the connector on the suspect engine retarder solenoid.

  5. Inspect the terminals on the solenoid connector for damage.

  6. Fabricate a jumper wire in order to short the two wires for the suspect solenoid on the solenoid connector. Crimp a pin to each end of the jumper wire.

  7. Make sure that the solenoid connector securely holds the jumper wire.

    Note: Worn terminals and/or damaged terminals on the solenoid connector could cause an intermittent "Open".

  8. Turn the key switch to the ON position.

  9. Access the "Special Tests" under the "Diagnostics" menu.

  10. Start the "Retarder Brake Test" on Cat ET.

  11. Once Cat ET displays the status of the engine retarder solenoid, stop the "Retarder Brake Test".

  12. Check for active diagnostic codes and/or logged diagnostic codes that are associated with the retarder solenoids.

Expected Result:

A high current diagnostic code (06) is logged at this time.

Results:

  • OK - A high current diagnostic code (06) is logged at this time. The harness wiring between the solenoid connector for the suspect engine retarder solenoid and ECM connector P2 is OK.

    Repair: Temporarily connect a new engine retarder solenoid.

    Temporarily connect a new engine retarder solenoid to the harness, but do not install the new engine retarder solenoid in the engine. Verify that there are no active diagnostic codes for the engine retarder solenoid. If there are no active diagnostic codes for the engine retarder solenoid, permanently install the new engine retarder solenoid. Clear any logged diagnostic codes.

    STOP

  • Not OK - A low current diagnostic code (05) is active at this time. The ECM did not recognize the short circuit.

    Repair: Repair the harness between the connector for the engine retarder solenoid and the valve cover connector for the suspect engine retarder solenoid.

    Verify that the repair eliminates the problem.

    STOP

Test Step 8. Create an Open Circuit at the Engine Retarder Solenoid

  1. Turn the key switch to the OFF position.

  2. Reconnect the valve cover connector.

  3. Remove the valve cover.

  4. Disconnect the connector on the suspect engine retarder solenoid.

  5. Inspect the terminals on the solenoid connector for damage.

  6. Turn the key switch to the ON position.

  7. Access the "Special Tests" under the "Diagnostics" menu.

  8. Start the "Retarder Brake Test" on Cat ET.

  9. Once Cat ET displays the status of the engine retarder solenoid, stop the "Retarder Brake Test".

  10. Check for active diagnostic codes and/or logged diagnostic codes that are associated with the retarder solenoids.

Expected Result:

A low current diagnostic code (05) is active at this time.

Results:

  • OK - A low current diagnostic code (05) is active at this time. The ECM recognized the open at the engine retarder solenoid. The harness wiring between the solenoid connector for the suspect engine retarder solenoid and ECM connector P2 is OK.

    Repair: Temporarily connect a new engine retarder solenoid.

    Temporarily connect a new engine retarder solenoid to the harness, but do not install the new engine retarder solenoid in the engine. Verify that there are no active diagnostic codes for the engine retarder solenoid. If there are no active diagnostic codes for the engine retarder solenoid, permanently install the new engine retarder solenoid. Clear any logged diagnostic codes.

    STOP

  • Not OK - A high current diagnostic code (06) is logged at this time. The ECM did not recognize the open.

    Repair: Repair the harness between the connector for the engine retarder solenoid and the valve cover connector for the suspect engine retarder solenoid.

    Verify that the repair eliminates the problem.

    STOP

Test Step 9. Check the Status of the Engine Retarder Switch

  1. Turn the key switch to the ON position.

  2. Monitor the status for "Retarder Off/Low/Med/High Switch" on Cat ET.

  3. Operate the engine retarder switch in the ON position and the OFF position. Also, operate the engine retarder switch in the Low, Medium, and High positions.

Expected Result:

The status for "Retarder Off/Low/Med/High Switch" correlates to the position of the engine retarder switch.

Results:

  • OK - The engine retarder switch is operating correctly. Proceed to Test Step 11.

  • Not OK - There is a problem in the circuit for the engine retarder switch. Proceed to Test Step 10.

Test Step 10. Check the Switch Circuits at the Firewall Bulkhead Connector

  1. Turn the key switch to the OFF position.

  2. Disconnect the firewall bulkhead connector. Remove the three wires for the retarder off/low/medium/high switch from the firewall bulkhead connector.

  3. Insert a jumper wire between the following wires on the vehicle harness:

    • AP Sensor/Switch Sensor Common

    • Retarder Solenoid Low/Hi Switch

  4. Turn the key switch to ON position.

  5. Check the status for "Retarder Off/Low/Med/High Switch" on Cat ET. Remove the jumper wire.

  6. Turn the key switch to OFF position.

  7. Insert a jumper wire between the following wires on the vehicle harness:

    • AP Sensor/Switch Sensor Common

    • Retarder Solenoid Med/Hi Switch

  8. Turn the key switch to ON position.

  9. Check the status for "Retarder Off/Low/Med/High Switch" on Cat ET.

Expected Result:

The status for "Retarder Off/Low/Med/High Switch" indicates "Low" when the common wire and the wire for the retarder low/high switch is jumped.

The status for "Retarder Off/Low/Med/High Switch" indicates "Medium" when the common wire and the wire for the retarder medium/high switch is jumped.

Results:

  • OK - The status changed accordingly. There is a problem in the vehicle harness in the cab.

    Repair: Repair the harness or replace the harness in the cab.

    Reconnect all wires and connectors.

    Verify that the repair eliminates the problem.

    STOP

  • Not OK - There is a problem between the ECM and the firewall bulkhead connector.

    Repair: Repair the harness or replace the harness between the ECM and the bulkhead connector.

    Reconnect all wires and connectors.

    Verify that the repair eliminates the problem.

    STOP

Test Step 11. Check the Operating Parameters of the Engine Retarder

  1. Turn the key switch to the ON position.

  2. Access the "Configuration" screen on Cat ET. Review the programming of the following parameters:

    • "Engine Retarder Mode"

    • "Engine Retarder Minimum VSL Type"

    • "Engine Retarder Minimum Vehicle Speed"

    • "Engine Retarder Delay"

  3. Use the following information when the parameter for the "Engine Retarder Mode" is being reviewed:

    1. If the parameter is programmed to Latch mode or to Coast mode, the engine retarder will not turn on unless the following conditions are met:

      • The cruise control On/Off switch is on.

      • The service brake pedal has been depressed.

  4. Use the following information when the parameter for the "Engine Retarder Minimum VSL Type" is being reviewed:

    • This parameter has no effect on engine retarder operation when the "Engine Retarder Minimum Vehicle Speed" is programmed to 0 mph.

    • When this parameter is programmed to the Hard Limit and the vehicle speed drops below the Engine Retarder Minimum Vehicle Speed, the engine retarder turns off.

    • When this parameter is programmed to the Soft Limit and the vehicle speed drops below the Engine Retarder Minimum Vehicle Speed, the engine retarder remains in the ON position.

  5. Use the following information when the parameter for the "Engine Retarder Minimum Vehicle Speed" is being reviewed:

    When the programmed value is more than 0 mph, the engine retarder will not turn on below the programmed value.

    Note: The retarder will not turn on if the vehicle speed is already below the "Engine Retarder Minimum Vehicle Speed".

  6. Use the following information when the parameter for the "Engine Retarder Delay" is being reviewed:

    This parameter provides a programmable delay once the conditions are met in order to turn the engine retarder.

Expected Result:

The problem is due to the programming of any of the listed parameters.

Results:

  • OK -

    Repair: Perform the following diagnostic procedure:

    Program parameters for desired operation.

    Refer to Troubleshooting, "Customer Specified Parameters" for additional information on the listed parameters.

    STOP

  • Not OK - The parameters are programmed correctly. Proceed to Test Step 12.

Test Step 12. Check the Accelerator Pedal

  1. Turn the key switch to the ON position.

  2. Monitor the status for "Accelerator Pedal Position" on Cat ET while the accelerator pedal is fully released.

  3. While the status is monitored, depress the accelerator pedal.

Expected Result:

The status for "Accelerator Pedal Position" is less than eight percent when the accelerator pedal is fully released. The status changes as the accelerator is depressed.

Results:

  • OK - The accelerator pedal is operating correctly. Proceed to Test Step 13.

  • Not OK - The accelerator pedal position sensor is not operating correctly.

    Repair: Refer to Troubleshooting, "Accelerator Pedal (Throttle) Position Sensor Circuit - Test".

    STOP

Test Step 13. Check the Clutch Switch

  1. Turn the key switch to the ON position.

  2. Monitor the status for "Clutch Pedal Position Switch" while the clutch pedal is fully released.

  3. While the status is monitored, depress the clutch pedal.

Expected Result:

The status for "Clutch Pedal Position Switch" is "Off" when the clutch pedal is fully released. The status is "On" when the clutch pedal is depressed.

Note: If a clutch pedal is not installed, select "OK".

Results:

  • OK - The clutch pedal position switch is operating correctly. There may be a mechanical problem with the engine retarder.

    Repair: Refer to Testing and Adjusting, "Compression Brake".

    STOP

  • Not OK - The clutch pedal position switch is not operating correctly.

    Repair: Refer to Troubleshooting, "Clutch Pedal Position Switch Circuit - Test".

    STOP

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