Audi Workshop Service and Repair Manuals > A3 Mk1 > Power unit | Motronic injection and ignition system (4-cyl.) | Mixture preparation system, electronic inj.,Gas | Checking additional signals

Motronic injection and ignition system (4-cyl.)

Checking additional signals

Checking vehicle speed signal

Notes:

◆ The vehicle speed signal is generated by the road speed sender -G68 (at the gearbox) and conditioned in the dash panel insert.
◆ The conditioned signal is received at contact 54 of the engine control unit, where it is used for idling speed stabilisation and damping of load change jolts on shifting gear.

‒ Connect vehicle diagnostic, testing and information system VAS 5051 or fault reader V.A.G 1551 and select engine electronics control unit with "address word" 01 .
Ignition must be on.

→ Indicated on display:

Rapid data transfer HELP

Select function XX

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

→ Indicated on display:

Read measured value block

Enter display group number XXX

‒ Press keys 0, 0 and 5 for "Display group number 5" and confirm entry with Q key.

→ Indicated on display:

Read measured value block 5 ⇒

1 2 3 4

Attention:
Attach fault reader to rear seat and operate it from there. Pay attention to safety precautions => Page 24-1.


	Display zones
	1	2	3	4
Display group 5: Vehicle speed
Display	xxxx rpm	x.xx %	xxx km/h	Text
Readout	Engine speed - ACTUAL (in increments of 40)	Engine load	Vehicle speed	Operating status
Operating range	min.: 660 rpm max.: 6800 rpm	min.: 0 % max.: 120 %	min.: 0 km/h max.: 250 km/h	Idle, part throttle, full throttle, overrun shut-off, acceleration enrichment
Specification	xxxx rpm	xxx %	Current vehicle speed	---
Note			Roughly the current vehicle speed must be displayed (approx. comparison with speedometer). If reading does not match specification, check wiring

If vehicle speed is not displayed:

‒ Connect test box V.A.G 1598/31 to engine control unit wiring harness. Actual engine control unit is not to be connected.

Check for short to positive/earth and open circuit in the following wiring.


Test box V.A.G 1598/31, socket	Dash panel insert, contact
54	=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

If no fault is found in wiring:

‒ Identify all components making use of vehicle speed signal (e.g. radio, automatic gearbox, air conditioner), consecutively disconnect them from dash panel insert and repeat test until cause has been established.

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