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Checking knock sensors > < Checking control unit power supply

A4 Mk1

Motronic Fuel Injection and Ignition System (4-cyl) Turbo
Checking ignition system
Checking knock control stop

If a fault entry relating to "knock control stop reached" is made, carry out the following checks:

  • ‒ Connect the 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
    For this purpose, the engine must be running at idle speed.
 
→ When indicated on display:
Rapid data transfer    HELP
Select function XX
  • ‒ Enter "08" to select the function "Reading measured value block" and confirm entry with Q key.
 
→ When indicated on display:
Reading measured value block    Q
Enter display group number XXX
  • ‒ Enter "020" for "display group number 020" and confirm entry with Q key.
 
→ Display readout:
Read measured value block 20    ⇒
    1    2    3    4
  • ‒ Check display in all display zones.

Display zones

1

2

3

4

Display group 020: Ignition knock control during driving

Display

xx.x °KW

xx.x °KW

xx.x °KW

xx.x °KW

Display

Ignition angle retardation cylinder 1 through
Knock control

Ignition angle retardation cylinder 2 through
Knock control

Ignition angle retardation cylinder 3 through
Knock control

Ignition angle retardation cylinder 4 through
Knock control

Specified value

0...12 °KW

0...12 °KW

0...12 °KW

0...12 °KW

Note:

Evaluation => Page 28-41

Note:

The indicated values in display zones 1 to 4 illustrate the actual ignition angle return through the knock sensor of the individual cylinders. The ignition angle retardation is carried out late in °KW (crankshaft degree).

Evaluation ignition angle retardation

Indicated on display

Possible causes of fault

Fault remedy

All cylinders greater than 12 °KW

- Knock sensor defective

- Check knock sensor => Page 28-42

- Connector corroded

- Knock sensor incorrectly tightened

- Loosen knock sensor and tighten to 20 Nm

- Loose components on engine

- Secure components

- Poor fuel quality

- Change fuel quality
(see operating instructions)

One cylinder deviates significantly from the others

- Connector corroded

- Check knock sensor => Page 28-42

- Engine fault

- Check compression:

- Loose components on engine

- Secure components

Checking knock sensors > < Checking control unit power supply