Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Fuel Injection System - Diesel: Testing: Microswitch
Connect Vacuum Tester (116 589 25 21 00) with "Y" fitting to EGR valve. At 1200 RPM, actuate microswitch. Vacuum on EGR valve should drop to 0 in. vacuum. Vacuum control flap should move into a deactivated position. Actuate microswitch. Vacuum control flap should move into deactivated position. If test is okay, end of test. If test is not okay, test individual components. See Fig 1 .
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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.