EGR input voltage low

[mrstg65]

Hello,

1999 Grand Prix SE 3.1 litre engine 162000 miles
Throws code P0401 low EGR flow.

I read on another thread that the voltage on the first terminal on the connector should be 12 volts, I am registering 2.5 volts on that terminal and 5 volts on the second. The remaining terminals show no voltage.

I have already removed the EGR valve and cleaned it with carb cleaner ( it was not bad at all ) , and there is sufficient vacuum and no blockages in the EGR tube.

Any thoughts as to whether this could be a PCM problem or if it is the EGR valve itself? Your time is appreciated.

[BNaylor]

Other parameters and components are used to test for sufficient EGR flow. When the EGR valve is commanded open during the test peak MAP (Manifold Absolute Pressure) is monitored over a set period of time. If incorrect the P0401 DTC will set. So check the MAP sensor and vacuum line(s) to it. Located on the back of the upper intake manifold area (UIM).

What vacuum reading are you getting off the UIM?

[mrstg65]

Thanks for the reply. The UIM vacuum reads 20 inches which is normal I think. A visual inspection of the MAP sensor and the vacuum line that connects to it found no problems. Is there a way to electrically test the MAP sensor? Another thing I notice is that the P0401 never sets unless there is less than 1/2 a tank of gas in the car. This could just be coincidence but it is worth noting.

[BNaylor]

18-22 in-hg of engine vacuum is considered normal. The evaporative emissions system uses engine vacuum so there might be a relationship with the EGR DTC. Have you checked all vacuum lines going back to the gas tank and fuel pump assembly? Also, at the evaporative emissions purge valve/solenoid engine side.

The MAP sensor is probably good if there are no MAP DTCs like P0107 or P0108.

Also, how old is your PCV valve and is the seal at the valve cover good?

[mrstg65]

I did not check the lines going to the tank and pump but that is a good idea. Where exactly is the purge valve/solenoid for the evap system?

PCV valve was changed at the onset of this problem but the seal was not. The valve slides in and out easily.. how tight is it for a normal fit? The o ring does not look damaged or dry rotted.

Thanks again.

[BNaylor]

Originally Posted by mrstg65

Where exactly is the purge valve/solenoid for the evap system?

It should be located driver's side of engine around the EGR valve and throttle body area.

Not so much on the GPs with the 3100 V6 engine, VIN "M" and "J" but PCV sealing is critical for ones with the Series II 3800 V6 engine. For example if an o-ring seal is left off the PCV or sealing not good at the UIM it will cause a P0401 DTC to set. But we mention it just for reference.

[mrstg65]

After reinstalling the MAP sensor and vacuum lines I drove my normal commute to work 40 miles 1 way mostly all highway.
The code did not reset and all 8 monitors are now running. I still have over 1/2 tank so I will watch this closely and post what happens.
It is dark now but I will check that solenoid tomorrow as well.

Thanks BNaylor for the good advice.