With Manufacturer's Scan Tool
Brake Light Switch -F- And Brake Pedal Switch -F47-, Checking
The diesel injection system operates with a throttle position sensor. For safety reasons, the engine is regulated when the brakes are operated. The ECM 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 is immediately reduced to idling speed. Incorrectly adjusted switches may lead to unwanted regulating action.
Special tools and equipment
- Scan Tool VAG 1551 or vehicle system tester
- VAG 1552 with cable VAG 1551/3
- Test box VAG 1598/31
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram
Check conditions
- The fuses must be OK.
- The battery voltage must be at least 11.5 V.
Test sequence
- Connect the Scan Tool VAG 1551 (VAG 1552) and with ignition switched on select engine electronics control unit with the "Address word" 01. (Connecting Scan Tool and selecting engine electronics control unit. [1][2][3]Connecting VAG 1551 Scan Tool)
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- for the function "Read measured value block" and confirm entry with -Q- button.
Indicated on display:
Read measured value block
Enter display group number XXX
- Press buttons -0-, -0- and -6- for "Display group number 6" and confirm entry with -Q- button.
- Observe display in display field 2.
Specification: 0 0 0
Read measured value block 6 ->
0 km/h 0 0 0 000000 255
- Operate brake pedal slowly.
Specification: 0 1 1 Both displays must change from 0 to 1 at same time.
Read measured value block 6 ->
0 km/h 0 1 1 000000 255
- Center display = Brake pedal switch
- Right-hand display = Brake light switch
- Release brake pedal slowly into rest position again.
Both displays must change from 1 to 0 again.
Read measured value block 6 ->
0 km/h 00 0 000000 255
- Press -> button.
- Press buttons -0- and -6- for the function "End output" and confirm entry with the -Q- button.
- Switch off ignition.
If one or both displays do not change:
- Check switches or wiring to the switches.
- Check DTC memory and, if necessary, repair any malfunctions and then erase. [1][2]Reading Diagnostic Trouble Codes
- Read-out the readiness code. If the DTC memory has been erased or the Diesel Direct Fuel Injection Engine Control Module - J248- was disconnected from permanent battery positive (B+), the readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes