Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

Or, hide this message: temporarily or permanently

EGR Valve Position Sensor: Description and Operation

EGR System Operation (typical):






The computer controlled portion of the EGR system consists of an EGR mounted lift sensor and a vacuum control solenoid in the vacuum box. The ECU contains memories for optimum EGR lift during various conditions. It reads actual EGR position from the lift sensor. The sensor uses a plunger operated potentiometer supply a signal to the ECU. If the EGR actual position differs from it's preferred position, the ECU cuts control solenoid power to reduce vacuum applied to the EGR valve. For additional information on the EGR system, refer to EMISSION CONTROLS.