Actron CP9087 - Manual (Page 22)

2-14
Testing Sensors
Section 2
Sensor operation (see page 2-15). Poor connec-
tions at the sensor or computer. Damaged or
sticking EGR valve. Worn or broken vacuum
hoses, vacuum connectors. Damaged vacuum
reservoir, canister. Problems with control solenoids
supplying operating vacuum to open EGR valve.
What to
Inspect
When to Test
• Related trouble codes sent by computer.
• Driveability problems such as hesitation,
stumble, surging, poor fuel economy, erratic
acceleration, knocking (pinging), no torque
converter lock-up.
Location
Attached to the top of the EGR valve.
How it is
used?
The computer is programmed to provide optimum
EGR flow during idle, cruise, and hard acceleration
operating conditions. The computer uses the
sensor signal to calculate actual EGR flow. Then
the computer can modify the EGR valve opening
as required.
What is it?
This sensor is a potentiometer - a type of variable
resistor (similar to a dashboard light dimmer
control). The computer supplies power and ground
to the sensor. the sensor has a shaft which is
pushed. When the sensor is mounted on the EGR
valve, the shaft gets pushed as the valve opens.
The sensor sends out a voltage signal indicating
the amount of valve opening (“lift”). The voltage
signal gets larger the more the valve is opened.
SENSOR
VOLTAGE
VALVE OPENING
HIGH
LOW
MAX. MIN.
FORD
EGR Valve
HONDA
EGR Valve