629-1147 | Genuine Cat® DEF - Diesel Exhaust Fluid Injector Kit

1. Inject DEF into exhaust

The injector sprays a fine mist of DEF into the hot exhaust gases leaving the engine.

2. Convert DEF into ammonia

Heat in the exhaust breaks the DEF (urea + water) down into ammonia (NH₃).

3. Neutralize harmful gases

The ammonia reacts with nitrogen oxides (NOx)—harmful pollutants produced during diesel combustion.

4. Turn pollutants into safe emissions

Through the Selective Catalytic Reduction (SCR) process, NOx is converted into:

• Nitrogen (N₂)
• Water vapor (H₂O)

5. Meet emissions standards

This process helps vehicles comply with regulations from agencies like the Environmental Protection Agency.

6. Maintain normal engine operation

Without a working DEF injector:

• The system can’t reduce emissions
• The vehicle may trigger warning lights
• It may limit power (limp mode)

1. Warning messages appear

• “Check Engine” light
• “DEF System Fault” or “Exhaust Fluid System” warning
  These are usually the first signs something isn’t working right.

2. Increased DEF consumption (or no usage)

• The system may use too much DEF (leaking or over-injecting)
• Or none at all (clogged or failed injector)

3. Poor emissions performance

• Higher nitrogen oxide (NOx) output
• May fail an emissions test regulated by the Environmental Protection Agency

4. Rough running or reduced efficiency

• Engine may feel slightly less efficient
• Fuel economy can drop because the system isn’t optimizing emissions properly

5. White crystal buildup (visible clue)

• Dried DEF can leave white crusty deposits around the injector or exhaust components
• This often means leaking or improper spray

6. Strong ammonia smell from exhaust

• Indicates DEF isn’t being properly atomized or burned in the SCR system

7. Engine power limitation (limp mode)

• The vehicle may reduce speed/power to force a repair
• Common in newer diesel trucks

8. No-start condition (severe cases)

• Some vehicles won’t restart if the DEF/SCR system failure isn’t fixed after repeated warnings