I have a 2001 mustang with a 3.8l I have a trouble code P0104

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.

Hi MIKE,maybe this PDFcan help you,Diagnostic Trouble Code Table ,good luck!

insufficient egr flow usually the dpfe sensor located in the back of intake manifold or mounted
on firewall.if you follow the wires/vacuum line from the egr valve you'll see it. common problem
& fairly easy job pick up a new 1 so you no what it looks like

good luck

P1491= "exhaust gas recirculation valve insufficient lift."
P0401= "exhaust gas recirculation insufficient flow"
P1739= ""3rd clutch pressure switch" (automatic transmission code)

the exhaust gas recirculation (EGR) valve is vacuum operated. there may be a vacuum line that is broken or leaking or become detached from the EGR valve. any vacuum leak will cause the engine to run lean, leading to poor starting and idle cut-off due to lean fuel fuel mixture.

The EGR valve has a vacuum diaphragm inside it. this diaphragm could be leaking. the EGR valve will need to be replaced if this is the case.

The P1739 code shows that a problem with the 3rd clutch pressure switch or the wiring leading to the switch has been detected. It may be an intermittent fault. Reset the trouble codes and drive for a while and see if this code returns. If so, check the wiring and switch operation of the 3rd clutch switch.

I believe this code is insufficient EGR flow. On this engine, the passages to the EGR valve often become carboned up and cause this code. Remove the EGR valve and inspect the passages to see if they need to be cleaned.

PO-401
EGR Flow Insufficient Detected

P0104 code is MAF or VAF. This can cause surging and rough running. If you disconnect the maf and find that it runs a little better, you can be sure that a maf replacement is in order. Double check the code by erasing it then roadtest. If code comes back then it is a hard code.

IT ALMOST SOUNDS LIKE YOU MAY HAVE A VACUUM LEAK SOMEWHERE. USE A LENGTH OF RUBBER HOSE AND HOLD IT UP TO YOUR EAR TO PIN-POINT THE LOCATION OF A VACUUM LEAK. HOPE THIS HELPS. LET ME KNOW PLEASE. THANK YOU IN ADVANCE FOR AN HONEST RATING AND THANKS FOR USING FIX-YA. P.S. EGR VALVE IS VACUUM ACTUATED

Insufficient EGR Flow Detected

Possible Causes:
DPFE sensor signal circuit is shorted to ground
DPFE sensor VREF circuit is open between sensor and PCM
DPFE sensor downstream hose off or plugged
DPFE sensor hoses both off, loose or damaged
DPFE sensor hoses connected wrong (reversed)
EGR orifice tube is damaged or restricted
PCM has failed
And what sets the code is…….Engine started, engine running in closed loop under steady cruise conditions, and the PCM detected the DPFE sensor input indicated insufficient EGR gas flow. Run the KOER Self-Test, and if DTC P1408 is present, the fault is currently present. This code sets in 2 Trip(s). The light will stay on until the cause is repaired. A bad EGR valve is only on possible cause.

Hope this helps,

Dave

The DPFE (Diferential Pressure Sensor)sensor is usually mounted on the engine and is connected to the pipe that runs from the exhaust manifold to the EGR valve with two rubber hoses. When the sensor goes bad, the Check Engine light comes on and typically sets any or all of teh following fault codes: P0171 & P0174 (lean codes), and/or P0401 (insufficient EGR flow). Nine out of ten times, the fault is not a bad EGR valve or a vacuum leak, but a bad DPFE sensor. A replacement costs about $112 at Ford, or about $48 at an aftermarket auto parts store.I hope this helps.