Toyota Fault Code
Free · no signupP0400
Black smoke; Rough idle; Hesitation; EGR cooler whistling sound.
System
Not specified
Symptom
Black smoke; Rough idle; Hesitation; EGR cooler whistling sound.
Diagnosis & fix steps
EGR Flow Malfunction.
LOGIC: The ECM doesn't see the expected change in Intake Pressure when the EGR valve opens.
ACTION: 1. Remove the EGR pipe and check for 50%+ carbon blockage.
2. Test the EGR vacuum solenoid or electric motor.
FIX: Clean carbon from EGR valve, cooler, and intake ports; replace EGR valve.
Red Seal field insights
In high-humidity Asian climates, the soot turns into a thick "tar." A thorough cleaning with a pressure washer or ultrasonic cleaner is often better than just replacing the valve.
Same code keeps coming back?
That's a program problem, not a part problem. Book a 30-minute uptime review with Grant, a Red Seal Heavy Duty Technician.
Read before you touch anything
- This is general reference information, not a repair manual. It is for trained, qualified technicians.
- Fault codes, meanings and procedures vary by model, serial number and software version. Confirm the code and the procedure against the manufacturer's service manual before acting.
- Follow the OEM service manual, torque specs and your site's safety procedures: lockout/tagout, block raised equipment, relieve hydraulic, fuel and air pressure, and let hot systems cool.
- You use this information at your own risk. Adventure Mechanical and AM Fleet Integrity accept no liability for damage, injury, downtime or loss arising from its use.
- Not affiliated with or endorsed by any manufacturer. Brand names are used only to identify the equipment a code applies to.
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