The EGR valve is mounted on the intake manifold and has an opening into the exhaust manifold.
The digital EGR valve, used on all 1990 and later EGR-equipped engines (Except the 2.5L and 1994-96 3.8L engine) is designed to control the flow of EGR independent of intake manifold vacuum. The valve controls EGR flow through 3 solenoid-opened orifices, which increase in size, to produce 7 possible combinations. When a solenoid is energized, the armature with attached shaft and swivel pintle, is lifted, opening the orifice.
The digital EGR valve is opened by the ECM, grounding each solenoid circuit individually. The flow of EGR is regulated by the ECM which uses information from the Coolant Temperature Sensor (CTS), Throttle Position Sensor (TPS) and Manifold Absolute Pressure (MAP) sensor to determine the appropriate rate of flow for a particular engine operating condition.
Digital EGR Valve Testing:
This system must be checked using a Tech 1®or equivalent scan tool. Steps 4, 5 and 6 must be done very quickly, as the ECM will adjust the idle air control valve to compensate for idle speed.
- Using a Tech 1®or equivalent scan tool, check for any diagnostic trouble codes and solve those problems first. Refer to the Diagnostic Trouble Code (DTC) lists later in this section.
- Select "EGR CONTROL'' on the scan tool.
- Start and run the engine, until it reaches normal operating temperature, then allow the engine to idle for 2 minutes.
- Energize EGR SOL #1; engine rpm should drop slightly.
- Energize EGR SOL #2; the engine should have a rough idle.
- Energize EGR SOL #3; the engine should idle rough or stall.
- If all tests were as specified, the system is functioning properly.
- If not, check the EGR valve, pipe, adaptor, gaskets, fittings, and all passages for damage, leakage or plugging. If all is OK, replace the EGR valve assembly.
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