Brother HL-2600CN Service Manual page 314

Error Code
Concerned Part Toner Sensor PCB.(LED side)
Confirm the connection of a toner sensor PCB.(LED side) connector.
Is DCN7 of IOD1 properly connected with a connector of the toner sensor ?
Check the voltage(LEDON-N/P)
Is a signal voltage between DCN7-7 and 9 to be a rising edge(+24V) ?
Is a signal voltage between DCN1-15 and 41 to be a trailing edge ?
Is E4 error cleared ?
Job is complete.
E4
YES
NO
YES
YES
NO
Connect them properly.
NO
Is E4 error cleared ?
YES
Replace the toner sensor PCB.
NO
Replace the IOD1 PWB 2.
NO
Replace the MCTL PWB 2.
DCN1
MCTL
1ICN
SGND
41
41
LEDON-N
15
15
YES
Toner Empty PCB.
IOD1
DCN7
LEDON-P
7
7 7
TLSCHK
8
8 8
SGND
9
9 9
Job is complete.
1
2
3