Briggs & Stratton VANGUARD M490000, Repair Manual

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2
18
DTC P0031 Signal Voltage Low (Non-Scan Diagnostics)
Step Action Yes No
1 1. Disconnect and reconnect O
2
sensor and ECM J2 (Black)
connectors.
2. Turn Ignition ON, Engine OFF. Clear codes.
3. Turn Ignition OFF, and then back ON.
4. Does DTC return?
Go to step 2. Problem corrected.
2 1. Turn Ignition OFF.
2. Back probe (using fused patch cord) terminal A (Red wire) on
engine side of O
2
sensor connector.
3. Connect terminal A back probe to red meter test lead on DVOM.
4. Back probe terminal D (Brown wire) on engine side of O2 sensor
connector.
5. Connect terminal D back probe to black meter test lead on
DVOM.
6. Set DVOM to read volts DC.
7. Turn Ignition ON, Engine Off.
8. Does DVOM read 12.2-13.5 volts DC?
Go to step 3. Perform visual and
continuity check
of Main Power
Relay and 20 amp
Battery fuse (Yellow).
Either there is no power
from fuse block or not
getting ground thru 5
volt return circuit.
3 1. Turn Ignition OFF.
2. Remove probe from terminal A, and back probe terminal B
(White/Green wire) on engine side of O
2
sensor connector.
3. Turn Ignition ON, Engine OFF.
4. Does DVOM read 12.2-13.5 volts DC?
Go to step 4. Replace O
2
sensor.
4 1. Turn Ignition OFF.
2. Remove probe from terminal B, and back probe ECM connector
terminal J2-07 (White/Green wire).
3. Turn Ignition ON, Engine OFF.
4. Does DVOM read 12.2-13.5 volts DC?
Both EFI wire harness
and O
2
sensor are good.
Go to step 5.
5 Are both O
2
sensor and ECM J2 connectors fully mated? Repair or replace EFI wire harness. Connect connectors.
O
2
Sensor Connector ECM J2 (Black) Connector Fuse/Relay Block
Not for
Reproduction