Great site!

I recently purchased a '98 ML320 and the check engine light came on. Took the vehicle to my BMW/Merc/Volvo mechanic that I have used for the passed 13 years for my BMWs.

Was told the codes were:

PO 442 - EVAP, LEAK
PO 460 - FUEL LEVEL SENSOR

Translation, "You need a new fuel pump"

I wanted to run this by the folks on this forum to confirm whether this is the case. The mechanic reset the system and the check engine light went off, yet it returned after a only been off for a couple of hours.

The vehicle seems to drive fine. There's no sluggishness nor other signs of poor performance.

So my questions are:

Was I given a correct diagnosis?
If it is the fuel pump, recommendations on the best place to purchase a new one? As I was quoted $515 just for the part.
Finally, how do I go about getting the maint. history of the vehicle?

Thanks!

Never heard of a PO code for the sender, so I'll reserve comment on that and research it if I have to, maybe someone else has heard of that code.

It would be interesting to know if BOTH of those codes came back. The evap leak code is pretty common.
Often times it's caused by a loose fuel cap or a defective cap, so make sure it's tight, look at the seal inside the rim of the cap, etc.
Another common cause for this code is a part inside the rear bumper called the "charcoal canister shut-off valve". To properly test the system requires a vacuum pump and a scanner (the one I'm familiar with is the Mercedes shop computer called SDS=star diagnosis system). The shop computer can do an over-ride operation and electrically shut this valve, at which time the vacuum pump is applied to the system under the hood at the purge valve, and the ability of the fuel system to hold vacuum is monitored. It can NOT leak MORE than 5mb in 1 minute or the system will set this fault code. Many things can cause the leak, but the 2 items I mentioned-the fuel cap or the charcoal canister shut-off valve-are the 2 most common.

There is a sensor that enable the engine computer to monitor all this stuff-it's mostly US required stuff only, called "OBDII", so thank the Feds for this problem. The sensor IS built into the fuel level sensor/fuel pump assembly, so maybe the code for the sensor is just nothing, not too sure (throwing that code because of an evap leak). The evap leak code is quite common, I'd tend to worry the most on testing the evap system as I have described.

Gilly

It was my understanding that both codes came back when checked. I will inspect the fuel cap and replace. Check engine light came on after wife filled-up, the other day.

She didn't leave the engine running while she filled it, did she?

Just see if the cap is tight first, I assume the folks checking ht ecodes would have done that though. Just look the seal over good, don't replace it without looking it over.

Gilly

Right On! Gilly! Had similar issues with the CEL. Tighten the gas cap "fixed" it each time. Called 18004Mercedes one time and the associate told me to just screw it. Anyhow, during the clamp recall service, asked the dealer to pull the codes and it turned out to be code P2013. Dealer replaced:

163-476-02-32 Valve
916002-012100 Clamp
005-997-45-90 Clamp

it says cause 47155737/18893 Charcol canister shut-off valve leaking.

Looks working very well bt far.

Gilly was right!

It was the charcoal canister shut-off valve. This along with the fuel filter and lines were replace.

Thanks for your help!

I have similar problem with 99 ML430. Check Engine light came on and I got P0446 and P0455 codes. Charcoal Canister Shut-Off Valve and Evap System leak. The fuel cap and rubber seal look good. I have Snap-on scanner and followed Gilly's procedure to do a vacuum test. No vacuum. I activated shut-off valve with the scanner and measured voltage at the valve on the back of the connector - 0 VDC. Positive 12 is there on the blue wire, but negative doesn't come from the pink wire. When I measure voltage with the connector disconnected from the valve I did see some activity on it while switching the valve on/off with the scanner, but not full 12 VDC. The valve coil reads 12 Ohm. It looks like pink wire has bad connection somewhere or ME module defective? I checked connector behind the rear left wheel and it looked good, no water or corrosion on the pins. Are there any more connectors for that wire on the way to the ME module?
Thanks, Mike

I don't think there is, not 100% sure. Try conducting your test at that seperation point you mentioned.

Gilly

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Found the problem: here is a picture of the connector on the frame behind the rear left wheel. When I checked it inside it looked good. However the second picture shows the pink wire close up. Insulation has a pin hole in it and greenish copper corrosion clearly visible there. No copper left inside. When I pulled the wire it got separated at this point. (Pic 3)
Fixed it by taking connector apart and soldering shortened wire to the pin.
Gilly thanks for your help,
Mike

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Second pic

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3rd pic

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