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 Monitor
This monitor applies to DTC P0400. Following conditions must be met during the test:
- Engine coolant temperature must be 176°F (80°C) or more.
- Atmospheric temperature is 41°F (5°C) or more.
- If automatic transmission, selector lever is in "D" range.
- If applicable, overdrive switch is in ON position.
- If applicable, pattern select switch is in OFF position.
- A/C switch is in OFF position.
Monitor takes about 10 minutes to complete. To run monitor, use illustration. See Fig 1 . Perform steps as follows:
- Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing.
- Start engine.
- Accelerate to 35-40 MPH.
- Keep speed constant for 20 seconds or more (M/T: 4th gear).
- Fully close throttle from engine speed of 2000-3000 RPM (M/T: keep clutch engaged) and decelerate to about 900 RPM without applying brakes. DO NOT turn steering wheel or operate light switch during this time.
- Accelerate to 35-40 MPH, then hold speed constant for 20 seconds or more (M/T: 4th gear). Repeat steps 4) and 5) seven more times.
- Return vehicle to shop and turn ignition off.
- Confirm DTC is not output. If DTC is output, go to appropriate DTC test in appropriate SELF-DIAGNOSTICS article.
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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.
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