Briggs & Stratton BIG BLOCK EFI, Repair Manual

Page: 44 / 142

40 Section 2: Troubleshooting DTCs
DTC P0131/P0132 Heated Oxygen (HO
2
) Sensor
Signal Voltage Low or High
Circuit Description
The HO
2
sensor voltage varies from about 1.0
volt if the exhaust is rich down to about 0.1 volt
if the exhaust is lean.
The sensor behaves like an open circuit and
produces no voltage when the exhaust tem-
perature is below 600°F (360°C). An open sen-
sor circuit or cold sensor causes an open loop
operation.
The sensor heater provides for faster sensor
warm-up. This allows the sensor to become
active in a shorter period of time and remain
active during a long extended idle.
An active DTC P0131 indicates that the sensor
has developed an open circuit and is operat-
ing in Open Loop mode. DTC P0132 indicates
circuit resistance is low and voltage being
returned to the ECM is too high.
Diagnostic Aids
Check for the following conditions:
Poor harness connection. Inspect harness
connectors for backed out terminals, improper
mating, broken locks, improperly formed or
damaged terminals, and poor terminal to wire
connection.
Always clear DTCs after performing repairs.
D C B A
Oxygen
Sensor
Signal
5 Volt
Return
Oxygen
Sensor
Heater
Control
J2 07 J2 10
J2 17
Inline
Connector
HO
Sensor
2
ECM
RED
WHITE/GREEN
GREY/BLACK
BROWN
VIOLET WHITE
GREY BLACK
From
Main Power Relay