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Oxygen sensor, Gauge operation, Troubleshooting – Actron CP7011 User Manual

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OxyGEN SENSOR

this sensor produces a voltage signal based on

the amount of oxygen it detects in the exhaust

stream. A low voltage (less than 0.4V) indicates a

lean exhaust (too much oxygen). A higher voltage

(0.6 - 1.0V) signals a rich exhaust (not enough

oxygen). the car computer uses the oxygen sensor

for fuel delivery attempting to maintain an ideal

air/fuel mixture for low emissions and good fuel

economy.

GAUGE OPERATION

NOTE: Typical Air/Fuel Ratio Gauge operation is described

below. The operation may vary from vehicle to vehicle.

the gauge measures the voltage produced by

the oxygen sensor and displays it in real time on

a radial, led (light emitting diode) bar graph.

the leds are color coded for ease of viewing and

interpreting the gauge reading.

When the headlights are turned on, the gauge

background illuminates and the leds are dimmed

for easy night viewing.

When the key is in the On position and the engine

is cold and not running, all segments of the gauge

are off.

When the engine first starts, all segments of the

gauge are off since the sensor needs to warm up to

its operating temperature. the exact time depends

on whether the oxygen sensor is heated (less than

a minute) or non-heated (several minutes) and the

vehicle. On some vehicles the gauge may read

lean right away.

When the sensor reaches its operating temperature,

but the engine still has not reached the operating

temperature when the car computer takes over

(open loop), the gauge will most likely read rich.

When the engine is controlled by the car computer

(closed loop) and the car is cruising, the gauge

segments will swing between rich and lean. On

vehicles with an added oxygen sensor that do not

have a computer the gauge reading will change

depending on the engine condition, but will not

constantly swing like on the computer-controlled

vehicles.

When the throttle is open during heavy load, the

readings will move toward rich.

during deceleration, the readings will be in the lean

zone. during a hard deceleration, the computer

might lean out the mixture to the point where no

led segments will be lit.

TROUbLESHOOTING

A sluggish response of the Air/Fuel ratio gauge

may indicate a partially fouled oxygen sensor. If

the sensor degradation is confirmed, the sensor

should be replaced. A lean operation under load

is a sign of improperly functioning fuel delivery

system. this can lead to engine damage.Persistent

rich operation (not under heavy load) can lead to

poor fuel economy, fouled spark plugs, and poor

performance.

Figure 2

General Hookup

OXYgen

SenSOr

COnneCtOr

CA

r

COMPU

ter

tO HeAd lAMPS

Or tAIl lIgHtS

HeAdlAMP

SWItCH

+12V

POWer

tO engIne

blOCk grOUnd

bl

AC

k

green

WHIte

AIr/FUel gAUge

FUSe

bOX

red

Figure 3 -

1, 2, 3 & 4 - Wire Sensors

1-WIre

OXYgen SenSOr

2-WIre

OXYgen SenSOr

3-WIre

OXYgen SenSOr

COnneCt gren WIre

On AIr/FUel gAUge tO

SenSOr SIgnAl WIre

4-WIre

OXYgen SenSOr

grOUnd

grOUnd

SenSOr SIgnAl

SenSOr SIgnAl

SenSOr SIgnAl

SenSOr grOUnd

HeAter POWer

HeAter grOUnd

SenSOr grOUnd

HeAter POWer

SenSOr SIgnAl

HeAter grOUnd

Figure 4

Oxygen Sensor Operation