Audi Workshop Service and Repair Manuals > A3 Mk1 > Power unit | Simos injection and ignition system (4-cylinder) | Ignition system, glow plug system | Checking ignition system | Checking power supply to control unit

Test sequence

–	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. For this purpose, the engine must be running at idling speed.

–	If the engine does not start, please continue the test with the ignition switched on.

Indicated on display:

–	Enter “08” for the function “Read measured value block” and confirm entry with the Q key.

Rapid data transfer            HELP

Select function XX

Indicated on display:

–	Enter “004” for “Display group number 004” and confirm entry with the Q key.

–	Check display in display zone 2.

Reading measured value block                  Q

Enter display group number XXX

	Display zones
	1	2	3	4
Display group 004: Voltage supply with engine idling
Display	xxxx rpm	xx.x V	xxx.x °C	xxx.x °C
Readout	Engine speed	Battery voltage	Coolant temperature	Intake air temperature
Specification	xxxx rpm	12.0...15.0 V	The temperature reading should increase evenly	From ambient temperature to 120 °C

If specification is not attained:

–	Connect test box -V.A.G 1598/31- to wiring harness for engine control unit. Do not connect to the engine control unit itself.

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