GEAR 1T0256 - Caterpillar

The Compression Brake lash adjustment is critical for the correct operation of the compression brakes. Refer to Testing and Adjusting, "Compression Brake Lash - Adjust", for the correct procedure.Clear all "Active" codes using Cat ET before proceeding with the following procedure. Refer to Troubleshooting, "Diagnostic Capabilities - Clearing Active Codes for On Board Diagnostics (OBD)" for more information on clearing "Active" codes.Use this procedure for the following diagnostic trouble codes:
Table 1
Diagnostic Codes    
CDL Code     J1939 Code     Code Description
(code descriptions may vary)     Comments    
2533-5     1072-5     Compression Brake Low/High Solenoid #1 : Current Below Normal     The code is logged when there is an electrical or wiring problem with the brake assemble positioned over cylinder 3 and cylinder 4.    
2533-6     1072-6     Compression Brake Low/High Solenoid #1 : Current Above Normal     The code is logged when there is an electrical or wiring problem with the brake assemble positioned over cylinder 3 and cylinder 4.    
2535-5     1073-5     Compression Brake Medium/High Solenoid #1 : Current Below Normal     The code is logged when there is an electrical or wiring problem with the brake assembles positioned over cylinders 1 and 2 or cylinders 5 and 6.    
2535-6     1073-6     Compression Brake Medium/High Solenoid #1 : Current Above Normal     The code is logged when there is an electrical or wiring problem with the brake assembles positioned over cylinders 1 and 2 or cylinders 5 and 6.    The compression brake uses the engine in order to provide auxiliary braking for the machine. The compression brake reduces wear of the wheel brake components, brake oil temperature, and the chance for engine overspeed. The compression brake also aids in the controllability of the machine.The CAT Compression Brake consists of identical housing assemblies. Each housing assembly is positioned over two cylinders. The Low braking function is accomplished by activating the middle brake assembly. The middle brake assembly is positioned over cylinders 3 and 4. The Medium braking function is accomplished by activating the outside two brake assemblies. The outside brake assemblies are located over cylinders 1 and 2 and cylinders 5 and 6. The High braking function is accomplished by activating all the brake assemblies. The braking level (Low, Medium, or High) is application-specific, therefore some applications may not have all three levels.If the retarder is installed on the engine, the configuration parameter for the engine retarder must be set to "Enabled" for this function to operate. The engine ECM will activate the appropriate compression brake solenoids in order to meet the requested level of braking. "Compression Brake Solenoid Override"
The Compression Brake Low/High Override activates the brake on cylinders 3 and 4
The Compression Brake Med/High Override activates the brakes on cylinders 1 and 2 and cylinders 5 and 6The Compression Brake Low/High Override and Compression Brake Med/High Override are diagnostic overrides that are available on Caterpillar Electronic Technician (ET). Use the overrides to assist in troubleshooting problems in the