Specifications

Chapter 6: FRU Replacement and Fault Isolation Procedures
6-5
6.2.3 Fuser Assembly Problem: fault code U4
There is a problem with the Fuser Assembly.
Notes:
1. Without the diagnostic tool, skip steps 2 and 4 and continue.
2. Corresponding Control Panel Messages may be:
• Failure: 940 Fuser System
• If the message is "Failure: 910 Engine Ctrl PCB," suspect the fuser, not the MCU.
• If the message is "Failure: 910 Engine Ctrl PCB" suspect a missing or unseated
fuser or bad temperature sensor on the fuser, not the NVRAM.
3. This FIP may also fix Images that do not fuse.
4. Try reseating the fuser, look for the fuser lamp to light, and try the engine self test.
1. INITIAL ANALYSIS
Inspect the following components. Are they are compatible with your printer version, correctly
installed, not damaged, deformed, or contaminated?
Fuser Assembly MCU PWB
Heater Rod LVPS Assembly
Temperature Sensor Assembly
Yes No
Go to Step 2. Replace the problem components.
2. TEMPERATURE SENSOR ANALYSIS
Does fault code U4 appear after POWER–ON?
Yes No
Go to Section 6.3.6 Temperature Sensor Assembly Failure. Go to Step 3.
3. HEATER ROD ANALYSIS
Let the Heater Rod cool down. Does the Heater Rod glow when power is switched ON?
Yes No
Go to Step 4. Go to Section 6.3.5 Heater Rod Assembly Failure.
4. Does fault code U4 appear during Power–On Sequence?
Yes No
Go to Step 5. Go to Step 6.