Part 2 of 2

Chart C-7 (Part 2 Of 2):

Exhaust Gas Recirculation (EGR) System Check (Part 1 Of 2):

CIRCUIT DESCRIPTION
The Exhaust Gas Recirculation (EGR) system is controlled by the Powertrain Control Module (PCM). The PCM controls the vacuum being supplied to the EGR valve by energizing and de-energizing a solenoid.

The PCM uses information from various engine sensors to determine when EGR is necessary. Once the PCM has requested EGR by grounding the solenoid circuit, the PCM will monitor engine operating conditions to determine if exhaust gas flow has entered the intake manifold. When the PCM tests for EGR operation and no change in engine operating conditions are indicated, a Diagnostic Trouble Code (DTC) will set.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

NOTICE:
Be sure shop exhaust hose is not connected during Steps 1 and 2.

1. The remaining tests check the ability of the EGR valve to interact with the exhaust system. This system uses a negative backpressure EGR valve which should hold vacuum with engine "OFF."
2. When engine is started, exhaust backpressure at the base of the EGR valve should open the valve's internal bleed and vent the applied vacuum allowing the valve to seat. Because the shop exhaust hose is not installed at this time. do not allow the engine to run longer than 15 seconds.

DIAGNOSTIC AIDS
^ Vacuum lines should be thoroughly checked for proper routing and connections.
^ Also check vacuum lines for cracking, chafing, or breaks.