97 tracer P0401 code won't go away

Hi Joe

Like all solenoid valves, you can clean them with throttle body cleaner and then test the solenoid electronically with a 12 volt supply.

P0401 Exhaust EGR Flow Insufficient

Toyota Nation Forum https://www.toyotanation.com > threads > p0401-exha...
May 1, 2014 - The sensor is how the ECM determines there's insufficient EGR flow. It's on the intake-side of the system and if not enough exhaust-gases flow ...

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P0401 : EGR Flow Insufficient on 1996 Toyota Corolla

OBD-Codes.com https://www.obd-codes.com > forums > viewtopic
Jan 20, 2007 - on EGR codes, we recommend replacing the EGR, vacuum modulator and VSV (if equipped) and cleaning out the carbon buildup to the intake from the ...
If that finds nothing wrong, remove the EGR valve and bypass tube and check them for cleanliness and blockages. If they are blocked, follow your maintenance manual's instructions for cleaning them out so you do not damage the valve, then replace them and reset the ECM.

Insufficient EGR Flow - P0401 Code - Toyota

That's not what this code is about .P0401 - EGR Flow Insufficient Detected . Probably clogged egr passages .
P0401 - EGR Flow Insufficient Detected The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum.

• Vacuum supply
• EGR valve stuck closed
• EGR valve leaks vacuum
• EGR flow path restricted
• EGRVR circuit shorted to PWR
• VREF open to D.P.F. EGR sensor
• D.P.F. EGR sensor downstream hose off or plugged
• EGRVR circuit open to PCM
• VPWR open to EGRVR solenoid
• D.P.F. EGR sensor hoses both off
• D.P.F. EGR sensor hoses reversed
• Damaged EGR orifice tube
• Damaged EGRVR solenoid
• Damaged PCM

Perform KOER self-test and look for DTC P1408 as an indication of a hard fault. If P1408 is not present, look for contamination, restrictions, leaks, and intermittents.

I am not surprized. The chances that replacing an EGR valve will fix a code P0401 on ANY Ford vehicle is about 1/2 of 1 percent. You most likely either have clogged up EGR ports in your intake manifold, or you have a defective Delta Pressure Feedback EGR (DPFE) sensor.

To find out which it is, apply vacuum to the EGR valve vacuum port with the engine idling. The engine should stumble and/or stall. If it does not, your ports are clogged. If it does, the most likely cause of your problem is the DPFE sensor. However, the EGR vacuum control solenoid could also be the cause.
You cannot properly test the EGR vacuum control solenoid without the proper equipment, but you can check to make sure that there is manifold vacuum going into one side of the solenoid and you can check to make sure that there are no breaks or leaks in the line that runs between the solenoid and the valve. If you find any of these, repair as necessary. If you do not find a problem with the vacuum lines, then you can take a "guess" and replace the DPFE. If this does not work, then you can "guess" again and replace the solenoid. If it still does nort work, then you probably have a bad electrical circuit to the solenoid (once again, requiring the proper equipment to diagnose).

Please also review the following article: What Else Could Be Wrong?

This error means Exhaust Gas Recirculation Flow Insufficient Detected.

You can deatils on the following site http://www.permoveo.ltd.uk/tabid/122/OBD-Error-Code/P0401/Diagnostics/Hyundai/Default.aspx

but for convenience I have reproduced that information here:
.
Generic OBD Error Code Details for P0401 Exhaust Gas Recirculation Flow Insufficient Detected What does this mean? OBD Code P0401refers to
EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor EGR (DPFE). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0401 code means that OBD detected an insufficient amount of EGR. SymptomsPossible sumptoms of OBD code P0401
You may notice drivability problems such as pinging (a.k.a. pre-ignition knock) when the engine is under load or the vehicle is at higher speeds. There may also be other symptoms. CausesPossible causes of OBD code P0401
A code P0401 most likely means one or more of the following has happened: •The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced•There is a blockage in the EGR (tube), most likely carbon buildup •The EGR valve is faulty •The EGR valve may not be opening due to a lack of vaccuum Possible SolutionsIn fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit. •Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open •Clean out the EGR valve and/or tubing to remove deposits•Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)•Replace the DPFE sensor (with a good quality / OEM one)•Replace the EGR valve Related CodesP0400 P0402 P0403

More than likely you have a faulty EGR Valve Pressure Sensor, especially if your EGR Valve Pressure Sensor is the original metal type. The new sensor is made of plastic and doesn't corrode like the old design. This sensor is located on the Intake Manifold.



Here is the sensor: http://www.autozone.com/autozone/parts/2001-Mercury-Sable/EGR-Valve-Pressure-Sensor/_/N-jfkhrZ93y2i

It is also possible that the EGR Valve has a clogged port, but this is less likely.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

DTC P0401 - Insufficient EGR Flow

EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor EGR (DPFE). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0401 code means that OBD detected an insufficient amount of EGR.

Causes: A code P0401 most likely means one or more of the following has happened:
* The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
* There is a blockage in the EGR (tube), most likely carbon buildup
* The EGR valve is faulty
* The EGR valve may not be opening due to a lack of vaccuum

Possible Solutions: In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.
* Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open
* Clean out the EGR valve and/or tubing to remove deposits
* Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)
* Replace the DPFE sensor (with a good quality / OEM one)
* Replace the EGR valve


DTC P1401 - Differential Pressure Feedback Electronic Sensor circuit High Voltage

I think that you need a new DPFE; first check it, you could also have something restricted. There are ports in the throttle body that can cause this as well. Check THIS LINK.

Hope helps.

1. Have tried cleaning out the throttle body? Carb cleaner and a rag should do the trick. Also, try bypassing the vacuum solenoid. First, remove the vacuum line from the solenoid, start the car, and then connect the vacuum line directly to the EGR valve. The car should run very rough and die. If not, then there is still something blocking the system (since you replaced everything, it might be down in the pipe (between valve and exhaust)). Also, ensure that the vacuum is strong enough by ensuring that the lines sticks to your fingers. Final possibility is that your new sensor is bad. You can do a voltage check (with igntion turned toon: 1 wire at 5 volts, 1 wire at 0 volts and 1 wire at about .5 tp 1.1 volts). The aftermarket sensors are not always of the best quality.
   

P0401 insufficient EGR flow.

Possible causes:

• Fault in vacuum supply to EGR vacuum regulator solenoid.
• EGR valve stuck closed or iced.
• EGR valve diaphragm leaks.
• EGR valve or flow path restricted.
• EGR vacuum hose off, plugged or leaks.
• VPWR circuit open to EGR Vacuum Regulator solenoid.
• EVR circuit to PCM open.
• EVR circuit to PCM shorted to PWR.
• Differential Pressure Feedback EGR (D.P.F. EGR) sensor pressure hoses both connected improperly.
• D.P.F. EGR sensor pressure hoses reversed.
• D.P.F. EGR sensor VREF circuit open.
• Downstream pressure hose off.
• Downstream pressure hose plugged.
• Damaged orifice tube assembly.
• Damaged EGR Vacuum Regulator solenoid.
• Damaged D.P.F. EGR sensor.
• Damaged PCM.

P0443 indicates an intermittent EVAP canister purge valve circuit failure.
Possible causes:

• Intermittent EVAP canister purge valve or VPWR circuit open.
• Damaged EVAP canister purge valve.

Late suggestion; it may be that the code needs to be reset via a code reader and that the problem will remain in memory until forcibly removed. That is fairly common.

it is your EGR Valve. EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve
, an actuator solenoid, and a differential pressure sensor EGR (DPFE). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0401 code means that OBD detected an insufficient amount of EGR.

Causes A code P0401 most likely means one or more of the following has happened:

• The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
• There is a blockage in the EGR (tube), most likely carbon buildup
• The EGR valve is faulty
• The EGR valve may not be opening due to a lack of vaccuum

Possible Solutions In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.

• Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open
• Clean out the EGR valve and/or tubing to remove deposits
• Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)
• Replace the DPFE sensor (with a good quality / OEM one)
• Replace the EGR valve

LOCATION:
drivers side of the engine bay, just under the intake manifold plenum where the throttle body bolts up! If you take the air snokel off you'll see it better! It has a remote mountted vaccum solenoid with a 2 wire connector going to it that you should be able to see near the throttle body.
Follow the hose from the solenoid down to the valve and you'll find it!

hopes this helps-------lebones