Vehicle Speed Signal, Checking
Vehicle speed signal, checking
Special tools and equipment
- VAG1551 or VAG1552 Scan Tool (ST) with VAG1551/3 adapter cable
- VAG1598/22 test box
- Multimeter US1119 (Fluke 83 or equivalent)
- VW1594 connector test kit
- Wiring diagrams
Checking conditions
- Battery voltage: min. 11.5 volts
- Speedometer OK.
Checking
- Connect VAG1551 or VAG1552 scan tool and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with engine running at idle), Testing and Inspection
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-, -0- and -5- to input display group number 5 (005), and press -Q- button to confirm input.
Indicated on display (1-4 = display fields)
Read Measuring Value Block 5 ->
1 2 3 4
- Road test and compare indicated vehicle speed with value in display field 3 (2nd technician required).
WARNING!
When driving or riding in an airbag-equipped vehicle, NEVER hold the scan tool or other test equipment in your hands or lap while in motion. Objects between you and the airbag increase the risk of injury in an accident.
During a test drive in an airbag-equipped vehicle, test equipment must always be fastened to and operated from the rear seat by a second technician.
- Observe value displayed in display field 3.
If the specification is attained:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
Continuation
If no speed is indicated or the display values decrease when driving slowly:
- Connect VAG1598/22 test box to ECM harness connector.
- Connect multimeter to measure voltage between test box sockets 2 and 20.
- Switch ignition on.
- Lift vehicle at front left.
- Rotate front wheel and observe voltage display.
- Specification: between 0 and at least 4 volts fluctuating
If the display does not fluctuate:
- Check wiring between speedometer and vehicle speed sensor.