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.
EGR System - Diesel: Operation
The ECM controls EGR by controlling the amount of "on" and "off" time of EGR solenoid through input from engine speed sensor and TPS. To monitor ECM control of EGR, a MAP sensor is used to measure the amount of absolute pressure in EGR vacuum line. If a minor variation between calculated EGR and actual EGR is monitored by the ECM, the ECM will make a correction. If variation is too great for ECM to correct, an error is detected. ECM will go into default.
When ECM monitors EGR is not needed, the EGR vent solenoid operates to vent vacuum. The ECM also energizes EPR solenoid to close EPR valve at idle to lower exhaust backpressure.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.