Compression Brake Solenoid Circuit. Location of the compression brake solenoid. Schematic for the compression brake circuit

Troubleshooting C27 and C32 Engines for 773F and 777F Off-Highway Truck/Tractors and for the 775F Quarry Truck

Compression Brake Solenoid Circuit - Test

SMCS -

System Operation Description:

Use this procedure to troubleshoot any suspect problems with the compression brake solenoids.

Use this procedure for the following diagnostic codes:

• 2533-05 Compression Brake Low/High Solenoid #1 current below normal
• 2533-06 Compression Brake Low/High Solenoid #1current above normal
• 2534-05 Compression Brake Low/High Solenoid #2 current below normal
• 2534-06 Compression Brake Low/High Solenoid #2 current above normal
• 2535-05 Compression Brake Medium/High Solenoid #1 current below normal
• 2535-06 Compression Brake Medium/High Solenoid #1 current above normal
• 2536-05 Compression Brake Medium/High Solenoid #2 current below normal
• 2536-06 Compression Brake Medium/High Solenoid #2 current above normal

Note: A switch input to the brake Electronic Control Module (ECM) sets the status of the compression brake. The status is off or automatic. Software for the brake ECM controls the level of braking. The levels of braking are low, medium and high. The brake ECM requests the engine ECM in order to actuate the compression brake solenoids. The request is sent over the Cat data link.

Perform this procedure under conditions that are identical to the conditions that exist when the problem occurs. Typically, problems with the compression brake solenoids occur when the engine is warmed up and/or when the engine is under vibration (heavy loads).

"Compression Brake Solenoid Test"

The "Compression Brake Solenoid Test" is a diagnostic test that is available on Caterpillar Electronic Technician (ET). Use the "Compression Brake Solenoid Test" to assist in troubleshooting problems in the circuit for the compression brake. The engine Electronic Control Module (ECM) will only detect shorts in the circuit for the compression brake 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 compression brake 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.

Note: The engine speed must be zero before the "Compression Brake Solenoid Test" will function.

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Remove electrical power from the engine's ECM. A strong electrical shock hazard is present if the electrical power is not removed from the engine ECM.

2. Thoroughly inspect connectors (1) and (2). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.