Obd2 codes p0401 and p1744

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

If you have replaced the EGR valve multiple times and followed the GM trouble chart, but the P0401 insufficient EGR flow code continues to recur on your 2000 Impala LS 3.8, there are a few other things you can check:

1. Check for clogged EGR passages: Make sure that the EGR passages in the intake manifold are not clogged with carbon buildup. Use a vacuum gauge to check for proper vacuum at the EGR valve to ensure the passages are clear.
2. Check the EGR solenoid: Make sure that the EGR solenoid is functioning properly. You can use a multimeter to test the solenoid's resistance and check for proper voltage and ground signals.
3. Check the vacuum supply: Make sure that there is adequate vacuum supply to the EGR valve. A vacuum leak or restriction in the vacuum line can cause insufficient EGR flow.
4. Check the catalytic converter: A clogged or damaged catalytic converter can also cause insufficient EGR flow. You can test the converter's efficiency using a digital thermometer.
5. Check the wiring and connectors: Make sure that all wiring and connectors related to the EGR system are in good condition and properly connected.

If none of these steps resolve the issue, it's possible that there is a problem with the PCM. You may need to have the PCM tested or replaced by a qualified mechanic.

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.

for p0401:
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.

P0401 - Exhaust Gas Recirculation Flow Insufficient Detected

Possible causes - Harness or connectors (EGR volume control valve circuit is open or shorted.)
- EGR volume control valve stuck closed
- EGR volume control solenoid valve
- Dead (Weak) battery
- EGR passage clogged
- Exhaust gas leaks Possible solution - Clean EGR Valve
- Repair EGR harness or connector
- Replaced EGR volume control solenoid valve
- Replaced EGR volume control valve

P0401 is a low egr flow code. It is rarely the EGR valve and more often than not the DPFE sensor that has failed. To find the DPFE sensor follow the metal tube from the EGR valve to the exhaust pipe. There will be two rubber hoses attached to that tube. The DPFE sensor will be on the other end of those hoses.

Make sure there are no holes in the rubber hoses. This can cause false codes as well.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

This code is an EGR code for insufficient amount of egr. It could be that the egr tube is clogged or the egr itself is bad or there is not enough vacuum to open the egr properly. There is also a sensor called the DPFE(differential pressure feedback egr) is faulty.

your egr valve may be bad or you mite be just clogged. take it off and see if there is any deris in egr vavle or the hole on to mounting service if so clean out. if not replace the egr valve.

Jason,
-after you change the part you have to reset/clear the code

-this can be done by either:
(1) using the OBD2 code reader that Autozone used OR since option 2 (below) is very quick
(2) disconnecting the battery for about 30 seconds (this will delete all codes/radio presets/etc) but it will also clear the 'check engine' code
-this is what I do AFTER i write down my radio station presets :)

-hopefully the new EGR valve resolves your issue after you CLEAR the code
...but that code just means a an insufficient amount of Exhaust Gas recirculation (pressure difference) used to keep the emissions in check
-if it comes back, then there are a few other fixes to try also

-let me know if you need further assistance
-please remember to rate me `fix-ya`if it works
thanks

P1744 is probably the TC going on the way out. :(

P 340 is probably the sensor itself. Don't get the Dorman one if it is the OHV motor.

P 401 is probably a bad DPF EGR sensor.