Brother HL-3450CN Service Manual page 288

Error Code
Name of Part Developer Clutch (DCLK)
Confirm the connection of Connector.
Is the connection proper between ECN13 of IOD2 and Clutch (DCLK) ?
Is the harness of Clutch (DCLK) broken ?
YES
Check the voltage at DCLK ON-N.
+24V
Does the voltage drop ( ) between ECN13-4 and ECN2-6?
NO
Does the voltage jump ( ) between ECN1-4 and ECN2-12 ?
NO
Replace current MCTL PWB with a new one.
Is D4 Error cleared ?
YES
Complete
D4
NO
YES
YES
NO
8-25
Connect the harness.
Connect the connector properly.
Is D4 Error cleared ?
NO
Replace the clutch (DCLK) with a new clutch.
Replace IOD2 PWB with a new one.
Is D4 Error cleared ?
NO
MCTL
Re-check
12CN
HL-3450CN SERVICE MANUAL
YES
Complete
YES
Complete
IOD2
14
18
ECN1 ECN13
DCL(K)ON-P
+24V-1
4
4 1
DCL(K)ON-P
3
ECN2
+24V-1 3
PGND
6
SGND
8
DCLK