Testing road speed signal — AUDI

ARG AVV
Notes:

The road speed signal is generated by the road speed sender -G68 (on the gearbox) and is processed in the dash panel insert.
The processed signal goes to contact 54 on the engine control unit and is used for idling speed stabilisation and for the damping of load change jolts when changing gear.

Connect vehicle diagnostic, testing and information system VAS 5051 (or fault reader V.A.G 1551) and select engine electronics control unit by entering address word "01" ( => Page
01-3
.)
When doing this the engine must be idling.

Rapid data transfer
HELP
Select function XX
Indicated on display:

Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

Read measured value block
Enter display group number XXX
Indicated on display:

Press keys 0, 0 and 5 to select Display Group 5 and confirm entry with Q key.

Read measured value block 5
⇒
1
2
3
4
Indicated on display:

Take vehicle for a test drive.

Important:
Secure fault reader to rear seat and operate from this location. When doing this, always observe the relevant safety precautions => Page
24-1
.
Check display value for vehicle speed.

Display zones
1 · 2 · 3 · 4
Display Group 5: Vehicle speed
Display · xxxx rpm · xxx.xx % · xxx km/h · Text
Indicates · Actual engine speed / (in steps of 40 rpm) · Engine load · Vehicle speed · Operating status
Range · min.: 750 rpm / max.: 6800 rpm · min.: 0 % / max.: 120.00 % · min.: 0 km/h / max.: 250 km/h · Idling / part throttle / full throttle / overrun cut-off / acceleration enrichment
Specification · xxxx rpm · xxx.xx % · current / speed · ---
Note · The display should show the approximate current speed (compare with speedometer / reading). / If readout does not match specification, test wiring / =>Page 24-194

If the vehicle speed is not displayed:

Connect test box V.A.G 1598/31 to wiring harness for engine control unit. Do not connect to the engine control unit itself.
=> Page
24-10
.

Test the following wiring connections for open circuits and short to positive or earth.

Test box V.A.G 1598/31, socket · Dash panel insert, contact
54 · => Current flow diagrams, Electrical fault finding and Fitting locations binder

Resistance in wiring: max. 1.5 ω

Rectify any open/short circuit as necessary.

If no wiring fault is detected:

Establish which electrical "consumers" (e.g. radio, automatic gearbox, air conditioner etc.) are using the speed signal, disconnect them one by one from the dash panel insert, then keep repeating the test until the cause of the problem has been identified.