The EGR solenoid controls the amount of vacuum to the EGR valve. The signal from the ECM is Pulse Width Modulated (PWM) which varies the on-off time (duty cycle) from 0-100 percent. Vacuum to EGR valve is controlled by EGR solenoid cycling. When EGR solenoid is on, there is no EGR vacuum.

The EGR vent solenoid operates to allow rapid venting of EGR vacuum to improve driveability and performance when the ECM recognizes the operating range for no EGR flow. When the solenoid is on, EGR vacuum is vented.

Both solenoids operate on 12 volts supplied by the ignition. The ECM supplies the ground to turn the solenoids on.

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

This step checks for EGR vacuum at idle. Normally, there should be full EGR vacuum at idle (above 20 in. Hg).
This step ensures ground in circuit would energize either solenoid. At idle, neither solenoid should be on. A test light on indicates a faulty ground in the circuit.
This step checks for complete circuits to both solenoids. The test light should normally be on.
In the 3.9k mode, the tester should turn the vacuum off to the EGR valve by ECM activation of the EGR vent solenoid. If vacuum is present, the ECM was not able to energize the EGR vent solenoid.

Fig 1: EGR/EGR Vent Check

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

EGR/EGR Vent Check

Use the Manual With the Right Hardware

When to See a Mechanic

Rather have a pro handle this?