Part 3 of 3

EGR Testing Part 3 Of 3:

EGR Wiring Diagram:

CIRCUIT DESCRIPTION:

The ECM operates a vacuum solenoid to control the EGR valve. The solenoid is normally closed. The ECM provides a ground path to energize the solenoid. This allows vacuum to flow to the EGR valve.

The ECM control of the EGR valve is based on the following;

^ Vehicle speed is above 50 mph.

^ Manifold pressure is between about 60-70 kPa (BARO 100 kPa) at low altitudes or through 30-40 kPa (70 kPa BARO) at the higher altitudes.

^ TPS is between 9% and 20%.

^ No more than 0.4% change in the TPS while the test is being run. The ECM control of the EGR valve is based on the following inputs;


TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.


6. The remaining tests check the ability of the EGR to interact with the exhaust system. This system uses a NEGATIVE BACKPRESSURE EGR VALVE which should hold vacuum with the engine off.

7. When the engine is started, exhaust back pressure at the base of the EGR valve should open the valve's internal bleed and and vent the applied vacuum allowing the valve to seat.