Brake Light Switch -F- and Brake Pedal Switch -F47-, Checking
Brake Light Switch -F and Brake Pedal Switch -F47, checking
Since the fuel injection system operates with an accelerator pedal sensor (potentiometer) which may be faulty, the engine is throttled back for reasons of safety when the brakes are applied. To do this the control module requires signals from the brake light switch and also the brake pedal switch.
This means, that if the brakes are operated when the accelerator pedal is held at a constant position the engine speed is immediately reduced. Incorrectly adjusted switches may lead to unintentional regulating process
- Connect Vehicle Diagnostic, Testing and Information System VAS5051 or VAG 1551 Scan Tool and select engine electronics control module by entering address word "01",Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1551/ VAS 5051 Scan Tool" Testing and Inspection . When doing this the ignition must be switched on.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select function "Read Measuring Value Block" and confirm entry with -Q- button.
Indicated on display
Read Measuring Value Block
Input display group number XXX
- Depress brake pedal
- Press buttons -0-, -6- and -6- to select "Display Group 066" and confirm entry with -Q- button.
Indicated on display
Read Measuring Value Block 86 ->
1 2 3 4
- Observe display in display field 2.
Relevance of figures in 4-digit readout in display field 2
- Allow brake pedal to return slowly to its normal position.
- Both readouts should return from 1 to 0.
If one or both of the displays does not change from 0 to 1:
- Check voltage supply.
Checking voltage supply
- Remove storage compartment on driver's side.
- Disconnect 4-pin harness connector on brake pedal.
- Connect multimeter (voltage range) between the following sockets on the connector:
- Switch ignition off.
4-pin connector on wiring Specification
harness, socket
1 + Ground (GND) Battery voltage
- Switch ignition on.
4-pin connector on wiring Specification
harness, socket
3 + Ground (GND) Battery voltage
If specifications are obtained:
- Check wiring connections.
If specifications are not obtained:
- Check wiring connections from sockets 1 and 3 of connector for open circuit or short to Ground (GND).
- Correct any open/short circuit as necessary.
Checking wiring connections
- Connect VAG1598/31 test box to wiring harness for engine control module. DO NOT connect to engine control module itself, Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1598/31 Test Box" Testing and Inspection
- Test following wiring connections for open circuits and short to B+ or Ground (GND):
4-pin connector on VAG 1598/31 test box socket
wiring harness, socket
2 56
4 55
Resistance in wiring: max. 1.5 ohm
- Correct any open/short circuit as necessary.
If no open circuit is identified in the wiring:
- Replace brake light switch/brake pedal switch.
- Display readiness code, Refer to "Monitors, Trips and/or Drive Cycle (Readiness Codes)/Displaying Readiness Code" Testing and Inspection . Readiness code must be generated if DTC memory was erased, Refer to "Monitors, Trips and/or Drive Cycle (Readiness Codes)/Generating Readiness Code" Testing and Inspection