TG. MFI #9 Main Relay Power Supply Absent

TG. MFI#9

MFI #9 Main relay power supply absent




Conditions for fault messages:
Fault message is logged if voltage is under 1 V.

Causes of fault:
Break in the system relay.
Break in the wiring between MFI#21 and system relay.

Fault symptoms:
The engine will not start.
If the fault is Intermittent the engine will stop or run rough.

TG1




Volvo ST, Test box
- Disconnect the ST in accordance with QA2. QA. Connecting The Volvo Scan Tool (ST)
- Connect the test box to MFI and check GND points in accordance with P1-P2. P. Test Box, Signal Description
^ Continue with Checking the power supply MFI#21 TG2.

TG2




Checking the power supply MFI#21
- Connect the control module to the test box.
- Install the fuse.
- Ignition off.
Connect a voltmeter between MFI#21 and MFI#5.
The voltmeter should read battery voltage.

If this value is OK:
^ Check the control of MFI #21 TG3.

If the reading is incorrect:
^ Test system relay MFI#21 TG6.

TG3




Checking the control of MFI#21
- Ignition on.
The voltmeter should read approx. 0.8 V.

If this value is OK:
^ Check MFI#9 TG4.

If the reading 18 incorrect:
^ Try using a new control module.

TG4




Checking MFI#9
- Ignition on.
Connect a voltmeter between MFI#9 and MFI#5.
The voltmeter should read battery voltage.

If this value is OK:
Intermittent fault.
^ Check the connections to MFI#21 and MFI#9 for loose contacts in accordance with NA5. NA. Checking the Wiring

If the reading is incorrect:
^ Test the system relay MFI#9 TG5.

TG5




Testing the system relay MFI#9
- Try using a new system relay.
Connect a voltmeter between MFI#9 and MFI#5.
The voltmeter should read battery voltage.

If this value is OK:
^ The system relay was broken.

If the value is still incorrect:
^ Check the wiring between MFI#9 and the system relay for breaks in accordance with NA2. NA. Checking the Wiring
^ Install the old relay.

TG6




Test system relay MFI#21
- Try using a new system relay.
- Ignition off.
Connect a voltmeter between MFI#21 and MFI#5.
The voltmeter should read battery voltage.

If this value is OK:
^ The system relay was broken.

If the value is still incorrect:
^ Check the wiring between MFI#21 and the fuse via the system relay for breaks in accordance with NA2. NA. Checking the Wiring
^ Install the old relay.