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Dieseljunky2
Dieseljunky2, ASE Certified Technician
Category: Toyota
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1996 Toyota Camry: Check engine light is lit; code p0401..egr..Exhaust

Customer Question

I have 1996 Toyota Camry, 2.2 liter. Check engine light is lit; Code P0401, which is EGR. Exhaust, gas insufficient flow. Changed EGR valve, VST valve, Checked vaccuum sources, changed vaccuum controller, also changed map sensor, checked for continuity at VST valve, and at the ECM. When light is cleared and car goes through a drive cycle light will come back on. Car does not have EGR temp sensor, so how does it know that there is insufficient flow?????
Submitted: 2 years ago.
Category: Toyota
Expert:  Dieseljunky2 replied 2 years ago.

Customer: Hello, have yo uh verified the egr passages are not stopped up? Apply a direct vacuum to the egr valve while the engine is idling. Does the engine stall or run very rough? If not, then the egr passages are clogged. Let me know what happens. Thanks
Customer :

Yes, I did and the car turns off immediately. Sorry I didn't include that earlier. Plenum is clear, the pipe from exhaust to EGR is clear also. What senses insufficient flow? On other Toyotas they have an EGR temperature sensor in the valve, which communicates insufficient flow to the ECM.

Dieseljunky2, ASE Certified Technician
Category: Toyota
Satisfied Customers: 3943
Experience: Hi, what issues are you having? Thanks
Dieseljunky2 and 9 other Toyota Specialists are ready to help you
Customer: replied 2 years ago.
I didn't mean to end our conversation. Do you have any other suggestions for the insufficient flow problem?
Expert:  Dieseljunky2 replied 2 years ago.
Put a vacuum gauge on the hose at the egr valve. Now flip the throttle full open a few times while running. Does the gauge move any? If not make sure the hoses are not cracked or stopped up. The system uses airflow to determine if egr is flowing.
Expert:  Dieseljunky2 replied 2 years ago.
Another thing, make sure you cannot blow through the solenoid valve with the electrical connector disconnected.
Customer: replied 2 years ago.

There isn't a blockage. I can't understand why the code is coming up insufficient flow when there isn't a blockage, and I replaced those parts as indicated earlier.

 

Expert:  Dieseljunky2 replied 2 years ago.
IS there vacuum to both the solenoid valve and vacuum valve? I have seen the fittings get carboned over.
Customer: replied 2 years ago.
All the parts are new.
Expert:  Dieseljunky2 replied 2 years ago.
I am referring to where the hoses attach to the manifold. Make sure there is vacuum there. If there is no vacuum, then there will be no egr flow.
Customer: replied 2 years ago.
Yes, there is vacuum there also.
Expert:  Dieseljunky2 replied 2 years ago.
Verify the vacuum lines on the vacuum valve. Big one on bottom to egr valve. The 2 small ones on top close to each other both go to manifold vacuum. The single small one goes to the solenoid valve.
Customer: replied 2 years ago.
Diesel, can you tell me what detects the flow on this car??? I have checked all hoses and valves and there is plenty of vacuum.
Expert:  Dieseljunky2 replied 2 years ago.
The airflow changes as the egr valve opens, replacing fresh air with exhaust gas. This changes the fuel to air mixture and the oxygen sensors pick up the different reading. Now, as a side note, if the thermostat is bad and the engine is not reaching full temp, it will prevent egr operation by activating the solenoid valve.
Expert:  Dieseljunky2 replied 2 years ago.
The coolant sensor for this is on the water outlet by the distributor. It is the 2 wire one closest to the head.
Customer: replied 2 years ago.
Thank you, Diesel. I'll try it later.
Expert:  Dieseljunky2 replied 2 years ago.
Ok

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