Main Relay (Computer/Fuel System): Testing and Inspection
Motronic Engine Control Module (ECM) Voltage Supply Relay -J271-, Checking
Special Tools and Equipment
- V.A.G 1526A multimeter
- V.A.G 1594A connector test kit
- V.A.G 1598/31 test box
NOTE: The Motronic Engine Control Module (ECM) voltage supply relay -J271- supplies voltage to the ignition coils with power output stages as well as the Engine Control Module (ECM) at pin 3 and a few additional components. With the ignition switched on, 12 Volts must be present at the respective ignition coil connector, terminal 1.
Test requirement:
- Ignition switched off.
Test sequence
- Pull off rubber seal of plenum chamber cover in direction of arrow.
- Remove cover -1- toward front.
- Remove cover for E-box, plenum chamber -arrows-.
- Pry off Engine Control Module (ECM) retaining bracket -arrow- using a screwdriver and set control module aside.
- Remove power supply relay from position -3- of 3-fold relay carrier, E-box, plenum chamber.
- Connect test box to wiring harness of Engine Control Module (ECM), ECM is not connected. Test Box, Connecting For Wiring and Component Test
- Check the following wire connection for open circuit according to wiring diagram:
3-fold relay carrier in Test box Socket
E-box, plenum chamber,
position 3 Terminal
4 23
Specified value: Wire resistance max 1.5 Ohms
- Check the wire for short circuit to B+ and Ground (GND).
- Specified value: Infinite Ohms (no continuity)
- If necessary, repair wire connection.
If no malfunctions are found in wire:
Checking voltage supply
- Connect multimeter for voltage measurement as follows.
3-fold relay carrier in Measure to
E-box, plenum chamber,
position 3 Terminal
1 Engine Ground (GND)
2 Engine Ground (GND)
Specified value: approx. battery voltage
If specified value is not obtained:
- Check wire connections for open circuit according to wiring diagram.
- Specified value: Wire resistance max 1.5 Ohms
If no malfunctions are found in wires:
Checking wire connection
- Check the following wire connection for open circuit according to wiring diagram:
3-fold relay carrier in Test box Socket
E-box, plenum chamber,
position 3 Terminal
8 Engine Ground (GND)
Specified value: Wire resistance max 1.5 Ohms
- Check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: Infinite Ohms (no continuity)
- If necessary, repair wire connection.
If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).
Assembly is performed in reverse order of removal, note the following:
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check DTC memory see "Mode 3: Check DTC memory". Mode 3: Check DTC Memory
2. If necessary, erase DTC memory see "Mode 4: Reset/erase diagnostic data". Mode 4: Reset/Erase Diagnostic Data
3. Generate readiness code. Readiness Code, Generating