Brake Light Switch: Testing and Inspection
Special tools and equipment
- VAG1551 Scan Tool (ST) or VAG1552 mobile scan tool with VAG1551/3 adapter cable
- VAG 1598/31 test box
- Multimeter (Fluke 83 or equivalent)
- VW1594 adapter set
- Wiring diagram
Test requirements
- Fuses 5,10,13 and 29 OK
- Battery voltage at least 11.5 V
Test sequence
- Connect VAG1551 (VAG1552) Scan Tool (ST)3. Refer to "On Board Diagnostic (OBD)/VAG1551 Scan Tool (ST), Connecting and Selecting Functions" under "Powertrain Management/Fuel Delivery and Air Induction/Fuel Injector", Testing and Inspection
- Switch ignition on and press buttons -0- and - 1- to insert "Engine Electronics" address word 01.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08 and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block HELP
Input display group number XXX
- Press buttons -0-, -6- and -6- to input display group number 66 (066) and press -Q- button to confirm input.
Indicated on display: (1-4 = display fields)
Read Measuring Value Block 66 ->
1 2 3 4
- Observe display in display field 2 (3rd and 4th positions from left):
Specified value: x x 0 0
- Depress brake pedal and observe display in display field 2.
Specified value: x x 1 1
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.
If the display does not change:
- Disconnect 4-pin harness connector from brake light switch and brake pedal switch.
- Measure resistance between terminals -1- + -4- of switch.
Specified value with brake pedal not depressed: infinity ohms
Specified value with brake pedal depressed: max. 1.5 ohms
- Measure resistance between terminals -2- + -3- of switch.
Specified value with brake pedal not depressed: 1.5 ohms
Specified value with brake pedal depressed. max. infinity ohms
If the specified values are not obtained:
- Replace brake light switch -F- and brake pedal switch -F47-
- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory. Refer to "On Board Diagnostic (OBD)/Diagnostic Trouble Code (DTC) Memory, Checking and Erasing (Scan Tool Functions 02 and 05)" under "Powertrain Management/Fuel Delivery and Air Induction/Fuel Injector", Testing and Inspection
- Display readiness code1. Refer to "On Board Diagnostic (OBD)/Readiness Code/Displaying" under "Powertrain Management/Fuel Delivery and Air Induction/Fuel Injector", Testing and Inspection
If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, the readiness code must be generated again. Refer to "On Board Diagnostic (OBD)/Readiness Code/Generating" under "Powertrain Management/Fuel Delivery and Air Induction/Fuel Injector", Testing and Inspection
If the specified values are obtained:
- Connect multimeter to measure voltage between terminal -1- and Ground (GND).
Specified value: at least 11.5 V
- Connect multimeter to measure voltage between terminal -2- and Ground (GND).
- Switch ignition on.
Specified value: at least 11.5 V
If the specified values are not obtained:
- Check wiring between 4-pin harness connector terminals 1 and 2 to central electrics using wiring diagram.
If the specified values are obtained:
- Remove wiper arms and plenum chamber cover.
- Connect VAG1598/31 test box to Engine Control Module (ECM) wiring harness. Engine Control Module (ECM) is not connected by this action.
- Check wiring between test box and 4- pin harness connector for open circuit according to wiring diagram.
- Terminal -3- + socket 55
- Terminal -4- + socket 56 Wire resistance: max. 1.5 ohms
- Additionally, check wires for short to one another.
- Additionally, check wiring for short to battery positive (B+) or Ground (GND).