FixVault

Brake Fluid Level: Diagnosis/Troubleshooting

NOTE:
  • If brake fluid reservoir level is too low, check if the Brake fluid level warning light is lit and remove the cause for the low level.
DIAGNOSIS/TROUBLESHOOTING - FAULT CODE 4281

Work instruction Display OK If not OK
1 Check brake fluid
  • Ignition on
  • Check brake fluid level
OK
 
Step 2
Correct the fluid level
 
End
2 Check ground supply line of level switch for open circuit
  • Ignition off
  • Pull plug off brake fluid level switch
  • Measure resistance between terminal 2 of plug on brake fluid level switch and ground
< 5
 
Step 3
Open circuit between pin 2 of plug on brake fluid level switch and ground
 
Repair wiring harness
End
3 Check level switch
  • Ignition off
  • Measure resistance between pins 1 and 2 of brake fluid level switch
approx. 100 (at 20 °C)
 
Step 4
Level switch faulty
 
Step 7
4 Check signal lead of level switch for short circuit to B+
  • Ignition on
  • Measure voltage between pin 36 of PSM control unit plug and ground
< 0.3 V
 
Step 5
Short circuit to B+ between terminal 36 of PSM control unit and pin 1 of brake fluid level switch
 
End
5 Check signal lead of level switch for short circuit to ground
  • Ignition off
  • Measure resistance between pin 36 of PSM control unit plug and ground
Step 6 Short circuit to ground between terminal 36 of PSM control unit plug and pin 1 of brake fluid level switch
 
End
6 Check signal lead of level switch for open circuit
  • Ignition off
  • Pull plug off PSM control unit
  • Measure resistance between pin 36 of PSM control unit plug and pin 1 of brake fluid level switch
< 5
 
Step 7
Open circuit between pin 36 of PSM control unit plug and pin 1 of brake fluid level switch
 
Repair wiring harness
 
End
7
  • Replace brake fluid level switch
End
8
  • Replace PSM control unit
End