Volkswagen Workshop Service and Repair Manuals

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Diode test lamp V.A.G 1527
• ◆ Adapter set V.A.G 1594
• ◆ Test box V.A.G 1598/31
• ◆ Current flow diagram

Check conditions

• ● → Fuse No. 34 must be OK.
• ● Battery voltage at least 11.5 V
• ● All electrical consumers, e.g. lights and rear window heating must be switched off.
• ● If the vehicle is equipped with an air conditioning system, this must be switched off.
• ● Engine speed sender must be OK, checking .
• ● The Hall sender must be OK,
  checking .

Test sequence

• ‒ Remove cover over camshaft housing , Fig.1 .
• ‒ → Pull 4 pin connector off ignition transformer (N152) -arrow-.

Checking voltage supply

• ‒ → Using multimeter and adapter cables from V.A.G 1594 measure the supply voltage between contacts 2 (positive) + 4 (earth) of disconnected connector.
• ‒ Switch on ignition.
       Specification: min. 11.5 V
• ‒ Switch off ignition.

If no voltage is present:

• ‒ → Check wire between 4 pin connector contact 2 and relay plate for open circuit according to current flow diagram.
       Wire resistance: max. 1.5 ω
• ‒ Check wire between 4 pin connector contact 4 and earth for open circuit according to current flow diagram.
       Wire resistance: max. 1.5 ω

Checking activation

• ‒ → Pull fuel pump fuse No. 40 out of fuse holder.

• ‒ → Connect diode test lamp V.A.G 1527 with adapter cables from V.A.G 1594 to
       contacts 1 + 4 (ignition output 1),
       contacts 3 + 4 (ignition output 2)
  of disconnected connector.
• ‒ Get a 2nd person to operate starter and check the ignition signal from engine control unit.
       The LED must flicker
• ‒ Switch off ignition.

If the LED flickers and there is voltage between contacts 2 + 4:

• ‒ Replace ignition transformer (N152)
  => Page 28-4 , item 4 .

The LED does not flicker:

• ‒ → Connect test box V.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.

• ‒ → Check wiring for open circuit between test box and 4-pin connector referring to current flow diagram.
       Contact 1 and test box socket 112
       Contact 3 and test box socket 113
       Wire resistance: max. 1.5 ω
• ‒ Additionally check wires for short to one another, to vehicle earth and to battery positive.
       Specification: ∞ω

If no wiring fault is detected and voltage was present between contacts 2+4:

• ‒ Replace engine control unit
  => Page 24-121 .

Checking secondary resistance

• ‒ → Check the secondary resistance on terminal 4 between
       Cyl. 1+Cyl. 4,
       Cyl. 2+Cyl. 3.
       Specification: 4.0... 6.0 kω (at room temperature)

If the specifications are not attained:

• ‒ Replace ignition transformer (N152)
  => Page 28-4 , item 4 .