Component Tests and General Diagnostics

Chart C-7A - Pulse Width Modulated (PWM) EGR:

Wiring Diagram for Chart C-7A - Pulse Width Modulated (PWM) EGR:

CHART C-7A - PULSE WIDTH MODULATED (PWM) EGR


Circuit Description:

PWM EGR is an ECM control that pulses the vacuum signal to the EGR. This is accomplished through an EGR solenoid that when energized by the ECM shuts off the vacuum to the EGR. This system can pulse the solenoid many times per second (PWM). The EGR solenoid is always energized (EGR off when the transmission is in park or neutral.


Test Description:

1. Checks to see if the EGR passages are restricted or if the valve is stuck open.

2. With the 4 wire EST connector disconnected, the ECM thinks the engine is not running. Grounding the test terminal, under this condition, causes the ECM to pulse the EGR solenoid "ON" and "OFF" for testing.


3. Checks EGR solenoid electrical control circuit. The test light should flash "ON" and "OFF" repeatedly if the ECM, harness and connections are OK.