Brake Signal: Testing and Inspection
Signal From Brake Light Switch And Brake Pedal Position Switch, Checking
Special tools and equipment
- Scan tool VAG 1551 or vehicle system tester V.A.G 1552 with cable VAG 1551/3B
- Test box VAG 1598/31
- Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
- Adapter set V.A.G 1594
- Wiring diagram
Test conditions
- All fuses must be OK
- The battery voltage must be at least 11.5 V
- All electrical consumers, e.g. lights and rear window heating must be switched off
Test sequence
- Connect scan tool VAG 1551 (V.A.G 1552). Switch ignition on and select engine control module with "Address word" 01.
Connecting scan tool and selecting Engine Control Module (ECM). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAG1551 Scan Tool" Testing and Inspection
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons 0 and 8 for function "Read Measuring Value Block " and confirm entry with Q button.
Indicated on display
Read Measuring Value Block HELP
Input display group number XXX
- Press buttons 0, 6 and 6 for "display group 66" and confirm with Q button.
Indicated on display (1-4 = Display zones)
Read Measuring Value Block 66 ->
1 2 3 4
- Observe display in display zone 2:
(3rd and 4th positions from left)
Specification: x x 0 0
- Depress brake pedal and observe display in display zone 2.
Specification: x x 1 1
- Press -> button.
- Press buttons 0 and 6 for the "End output" function and confirm input with Q button.
- Switch ignition off.
If the display does not change:
- Remove driver's storage compartment:
- Disconnect 4-pin connector off brake light switch and brake pedal position switch.
- Measure resistance between terminals 1 + 4 of the switch. Specification:
- Brake pedal not depressed: Infinity Ohms
- Brake pedal depressed: Max. 1.5 Ohms (no continuity)
- Measure resistance between terminals 2 + 3 of switch. Specification:
- Brake pedal not depressed: Max. 1.5 Ohms
- Brake pedal depressed: Infinity Ohms (no continuity)
If the specifications are not obtained:
- Replace brake light switch (F) and brake pedal position switch (F47).
- Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory. Refer to "Displaying and Reading Trouble Codes/With Manufacturers Scan Tool/DTC Memory Checking and Erasing" Testing and Inspection
- Read readiness code. If DTC memory has been erased or engine control module was disconnected from permanent positive, readiness code must be generated again.
Refer to "Monitors, Trips and/or Drive Cycle/Readiness Code, Displaying" Testing and Inspection
Refer to "Monitors, Trips and/or Drive Cycle/Readiness Code, Generating" Testing and Inspection
If the specifications are obtained:
- Connect multimeter to measure voltage between terminal 1 and Ground.
Specification: at least 11.5 V
- Connect multimeter to measure voltage between terminal 2 and Ground.
- Switch ignition on.
Specification: min. 11.5 V
If the specifications are not obtained:
- Check wiring between 4-pin connector terminals 1 and 2 to central electrics using wiring diagram.
If the specifications are obtained:
- Remove inner plenum chamber cover, left:
- Connect test box V.A.G 1598/31 to control module wiring harness. Engine control module is not connected by this action.
- Check wiring for open circuit between test box and 4-pin connector for open circuit using wiring diagram.
- Terminal 3 + socket 55
- Terminal 4 + socket 56
Wire resistance: Max. 1.5 Ohms
- Also check wires for short to one another.
- Also check wiring for short to battery positive or Ground.
If no wiring problem is detected:
- Replace Engine Control Module (ECM).