Code 53: EGR Vacuum Control: Notes

The EGR Vacuum Control is an ECM controlled solenoid that pulses manifold vacuum to the EGR valve. The control is always de-energized (EGR off) in Park or Neutral and at idle. The ECM controls the EGR vacuum by completing the ground to energize the solenoid. When the solenoid is energized, manifold vacuum opens the EGR valve. Part of the control is a vacuum diagnostic switch. Its purpose is to signal the ECM when vacuum is actually being applied to the EGR valve.

Code 53 will be set if the EGR diagnostic vacuum switch senses vacuum at idle, or if it does not sense vacuum in gear with moderate to heavy engine load, but less than WOT.

The EGR valve is energized based on the following inputs: Engine running above idle, but less than WOT, engine coolant temperature 42.5°C (108°F) or above, and transmission in gear.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

Check for presence of vacuum at idle. Normally there is no vacuum to the EGR at idle.
By grounding the diagnostic "test" terminal, the ECM will normally energize the solenoid. The test light should be "ON" if the solenoid circuit is okay.
Check for a complete circuit to the vacuum switch. If the circuit is complete, the reading will be about battery voltage.
This test checks for a faulty vacuum switch by substituting a vacuum gauge. The test light should be "OFF" if the switch is good.