Motronic Engine Control Module (ECM) Power Supply Relay -J271- and Activation, Checking
Motronic Engine Control Module (ECM) Power Supply Relay -J271- And Activation, Checking
Recommended special tools and equipment
- VAG1526A multimeter
- VAG1594A connector test kit
- VAG1598/31 test box
NOTE: The Motronic Engine Control Module (ECM) voltage supply relay -J271- supplies voltage to the ignition coils with power output stages and the Engine Control Module (ECM) at pin 121.
Test requirement:
- Ignition switched off.
Test sequence
- Remove cover -1- in engine compartment (left side).
- Remove coolant reservoir (arrow)
- Disconnect electrical wiring to Engine Coolant Level (ECL) Warning Switch -F66- at bottom of expansion tank.
- Lay aside coolant reservoir with connected coolant hoses -1- to -3-.
- Remove bolts (arrows) on cylinder head at left.
- Disconnect 4-pin harness connectors -4- to -6- at ignition coils.
NOTE: For further testing, connect the multimeter to harness connector in place of an ignition coil.
- Connect multimeter for voltage measurement as follows.
Harness connector Terminal Measure to
1 Ground (GND)
- Switch ignition on.
- Specified value: approx. battery voltage
- Switch ignition off.
If specified value is not obtained:
- Remove rubber seal for plenum chamber cover.
- Remove plenum chamber cover -1- toward front (arrows).
- Pry off both covers -3- using a screwdriver.
- Loosen hex-nuts -4- by several turns.
- Loosen wiper arm -2- from wiper axle by lightly tilting.
- Remove hex nuts completely and remove wiper arms.
- Disconnect securing clips -1- and remove cowl grill -5-.
- Remove cover for E-box, plenum chamber (arrows).
- Pry off Engine Control Module (ECM) retaining bracket (arrows) using a screwdriver and set control module aside.
- If installed, unclip Transmission Control Module (TCM) retaining bracket and set control module aside.
- Disconnect voltage supply relay -3-.
- Check the following wire connection for open circuit according to wiring diagram:
Relay carrier in E-box, plenum Harness connector
chamber, position 3 Terminal at ignition coils Terminal
8 1
- Specified value: Wire resistance max 1.5 Ohms
- If necessary, repair wire connection.
If no malfunctions are found in wires:
- Check voltage supply of Motronic Engine Control Module (ECM) voltage supply relay - J271-.
- Check activation of Motronic Engine Control Module (ECM) voltage supply relay -J271-.
Checking voltage supply
- Connect multimeter for voltage measurement as follows.
Relay carrier in E-box, plenum chamber, Measure to
position 3 Terminal
1 Ground (GND)
2 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
Checking activation
- Connect multimeter for voltage measurement as follows.
Relay carrier in E-box, plenum chamber, Measure to
position 3 Terminal
4 B+
- Switch ignition on.
- Specified value: approx. battery voltage
- Switch ignition off.
If specified value is not obtained:
- Connect test box to wiring harness of Engine Control Module (ECM); ECM is not connected.
- Check the following wire connection for open circuit according to wiring diagram:
Relay carrier in E-box, plenum chamber, Test box
position 3 Terminal Socket
4 23
- Specified value: Wire resistance max 1.5 Ohms
- Check wire for short circuit to B+ and to Ground (GND).
- Specified value: Infinity ohm (no continuity)
- If necessary, repair wire connection.
If no malfunctions are detected:
- Replace Motronic Engine Control Module (ECM) voltage supply relay -J271-.
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If DTC memory was erased, generate readiness code.
- End diagnosis and switch ignition off.