533-2738 | Genuine Cat® Diesel Exhaust Fluid Pump 24V

Part number is utilized across various Tier 4 Final / Stage V Caterpillar® machines and industrial engine platforms:

• Caterpillar® Excavators: 320, 323, 326, 330, 335, 336, 349, 352 series.

• Caterpillar® Wheel Loaders: 950M, 962M, 966M, 972M, 980M, 982M.

• Caterpillar® Track-Type Tractors (Dozers): D5, D6, D6T, D7, D8T.

• Caterpillar® Articulated Dump Trucks: 725, 730, 735, 740, 745.

• Cat® Industrial Engines: C4.4, C7.1, C9.3, C9.3B, C13, C15 ACERT Tier 4 Final / Stage V emissions configurations.

1. What is it?

Part is a 24-volt electrical supply pump that pressurizes and delivers Diesel Exhaust Fluid (AdBlue®) from the storage tank to the SCR dosing injector located in the exhaust stream. It ensures precise fluid metering required to break down harmful nitrogen oxide ($\text{NO}_x$) emissions into harmless nitrogen gas and water vapor.

2. Core Functions & Technical Features

• Precision Pressure Delivery: Maintains stable system pressure to ensure fine, consistent DEF atomization at the injector nozzle.

• Integrated Freeze Protection: Equipped with internal heating elements that melt frozen DEF in cold ambient conditions to protect internal diaphragms and maintain system readiness.

• Purge / Back-Sucking Cycle: Reverses fluid flow upon engine shutdown to drain residual DEF from the lines and injector, preventing chemical crystallization and ice expansion damage.

• 24V Heavy-Duty Electrical Design: Built to withstand harsh machine vibrations, dirt, and operating environments typical of construction, mining, and forestry job sites.

1. Active Diagnostic Fault Codes & Warning Lights

• Symptom: Check Engine Light (CEL), Emissions Warning Icon, or active Diagnostic Trouble Codes (DTCs) displayed on the Cat® Advisor / Messenger display.

• Common Fault Codes: Low DEF pressure / delivery flow, DEF pressure supply circuit open/short, or SCR system pressure building timeout.

2. Engine Horsepower & Speed Derate (Limp Mode)

• Symptom: Severe reduction in engine output power or machine operating speed, eventually progressing to a 100% power derate or idle-only lock out.

• Cause: EPA regulations force the Engine Control Module (ECM) to derate the engine when the SCR system cannot dose DEF fluid to control $\text{NO}_x$ emissions.

3. Inability to Build or Maintain DEF Pressure

• Symptom: The pump motor runs continuously without priming, or the pump shuts down shortly after startup due to insufficient pressure build-up.

• Cause: Clogged internal DEF filter screen, worn pump diaphragm/piston seals, or crystallized urea buildup blocking internal passageways.

4. Failure During Cold-Weather Operation

• Symptom: SCR system fault triggers only when operating in sub-zero ambient temperatures.

• Cause: Internal 24V DEF heater element failure, preventing frozen fluid inside the pump housing from thawing out.

5. Failure of the Post-Shutdown Purge Cycle

• Symptom: No audible reverse suction/purge pump noise after key-off, leading to lines freezing or clogging with dried white urea crystals.

• Cause: Damaged reversing valve, blown fuse/relay, or internal pump motor control board failure.