NOTE: Before testing EGR valve, confirm that altitude is lower than 4000 feet (1220 m). Make sure transmission is in neutral. If higher than 4000 feet, disconnect High Altitude Compensator (HAC) connector.

With engine temperature below 131°F (55°C), run engine while checking that EGR valve diaphragm is not operating. Check by touching diaphragm with finger. Diaphragm should be stationary.
CAUTION: The EGR valve may be hot. It may be necessary to wear gloves.
Warm engine to normal operating temperature. Increase engine speed while checking movement of diaphragm. Diaphragm should move away from piston side of EGR valve during acceleration. Decelerate engine and check that diaphragm moves toward piston side of EGR valve. See Fig 1 .
If EGR valve does not function properly, check vacuum hoses for leakage, clogs or deterioration. Test EGR valve using vacuum pump. Connect vacuum pump to Three-Way Solenoid Valve (TWSV) side of EGR valve. Apply .08 in. Hg vacuum to EGR valve and check that diaphragm moves smoothly and is held toward side of vacuum pump. See Fig 2 .

Fig 1: EGR Valve Diaphragm Movement
If EGR valve tests satisfactorily, check appropriate electronic control module circuits. See ELECTRONIC CONTROL MODULE article.

Fig 2: Testing EGR Valve with Vacuum Pump

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 Valve

Use the Manual With the Right Hardware

When to See a Mechanic