CEL is ON Codes p0171,p0174,p0443

[rathi60]

:help
02 E39 540i 45k miles
p0171,p0174-Lean on Bank 1 and 2
p0443-Evaporator purge valve
Occationally the car stalls when comming to a stop.
Is there two different issues I am looking at?
All your comments will be much appreciated.

[MaxVQ]

I think you have 2 problems:
(1) Vacuum leak somewhere
(2) Evap purge valve

The vacuum leak will cause the car to run lean, and it could stall at idle because of this. An engine at idle is the most sensitive to vacuum leaks.

Check your valve cover gaskets, intake boots, and all vacuum lines.

Thinking about it now, the codes may be related. The evap system needs vacuum to function. If you have a vacuum leak, this may cause the lean condition and the evap code. The only way to know is to fix the vacuum leak and see if the evap code comes back.

Good luck.

[Petes540i6]

Quick question: Is the vacuum for the fuel/air intake connected somehow to the "fuel/evaporative" system?

I had always thought that the "fuel/evaproative" system was slightly pressurized to self-diagnose for leaks, as opposed to being somehow connected to the vacuum of the fuel/air intake system.

I am also getting p0170, p0173 and p0443.

[jbrovage]

i'd check your gas cap, too.

[MaxVQ]

Quick question: Is the vacuum for the fuel/air intake connected somehow to the "fuel/evaporative" system?

I had always thought that the "fuel/evaproative" system was slightly pressurized to self-diagnose for leaks, as opposed to being somehow connected to the vacuum of the fuel/air intake system.

I am also getting p0170, p0173 and p0443.
You are correct!
From 04b_MS45_DME_Part_3.pdf
(This is for the E85, but I think it applies to the E39)


Evaporative Leakage Detection (DM TL):
This component ensures accurate fuel system leak detection for
leaks as small as 0.5 mm by slightly pressurizing the
fuel tank and evaporative components. The DM TL
pump contains an integral DC motor which is activated
directly by the ECM. The ECM monitors the pump
motor operating current as the measurement for
detecting leaks.

The pump also contains an ECM controlled change
over valve that is energized closed during a Leak
Diagnosis test. The change over valve is open during all
other periods of operation allowing the fuel system to
“breath” through the inlet filter. The DM TL is located
under the luggage compartment floor with the Carbon
Canister.

1. In its inactive state, filtered fresh air enters the evaporative
system through the sprung open valve of the
DM TL.

2. When the DME activates the DM TL for leak testing,
it first activates only the pump motor. This pumps air
through a restricter orifice (0.5 mm) which causes
the electric motor to draw a specific amperage
value. This value is equivalent to the size of the
restricter.

3. The solenoid valve is then energized which seals the
evaporative system and directs the pump output to
pressurize the evaporative system.
• A large leak is detected in the evaporative system if the amperage
value is not achieved.
• A small leak is detected if the same reference amperage is achieved.
• The system is sealed if the amperage value is higher than the reference
amperage.

Since MY 2002, a heating element is integrated in the
DM TL pumpto eliminate condensation. The heater is
provided battery voltage with “KL15” and the ECM provides
the ground path.

[gemnilvr]

You are correct!
From 04b_MS45_DME_Part_3.pdf
(This is for the E85, but I think it applies to the E39)


Evaporative Leakage Detection (DM TL):
This component ensures accurate fuel system leak detection for
leaks as small as 0.5 mm by slightly pressurizing the
fuel tank and evaporative components. The DM TL
pump contains an integral DC motor which is activated
directly by the ECM. The ECM monitors the pump
motor operating current as the measurement for
detecting leaks.

The pump also contains an ECM controlled change
over valve that is energized closed during a Leak
Diagnosis test. The change over valve is open during all
other periods of operation allowing the fuel system to
“breath” through the inlet filter. The DM TL is located
under the luggage compartment floor with the Carbon
Canister.

1. In its inactive state, filtered fresh air enters the evaporative
system through the sprung open valve of the
DM TL.

2. When the DME activates the DM TL for leak testing,
it first activates only the pump motor. This pumps air
through a restricter orifice (0.5 mm) which causes
the electric motor to draw a specific amperage
value. This value is equivalent to the size of the
restricter.

3. The solenoid valve is then energized which seals the
evaporative system and directs the pump output to
pressurize the evaporative system.
• A large leak is detected in the evaporative system if the amperage
value is not achieved.
• A small leak is detected if the same reference amperage is achieved.
• The system is sealed if the amperage value is higher than the reference
amperage.

Since MY 2002, a heating element is integrated in the
DM TL pumpto eliminate condensation. The heater is
provided battery voltage with “KL15” and the ECM provides
the ground path.



im not sure at all what u said or what that means but im having a diagnostic reading of:

po174 ?
po171 ?
po313 misfire with low fuel

would u happen to know what the first two might mean and explain the third one! do i need spark plugs and o2 sensors maybe!?

[TheMatrixz]

Beside the suggestions by MaxVQ, I would check the air intake hoses, from the air filter box to the body throttle making sure there's no rip anywhere that allows air leakage.

The evap valve is simple to replace, it takes about 10 minutes max and costs around $100.