Fuel System - MIL ON, Tank Leakage Fault Codes

GROUP 16
Fuel Systems

Bulletin Numbers
16 01 00

Woodcliff Lake, NJ
May 2000
Service Engineering

SUBJECT:
Check Engine Light Illuminated, "Tank Leak" Fault Stored in the [1][2]DME

MODEL:
E36, Z3, E38, E39, E46, E52, E53

Situation:
Customer complaint that the "check engine" light is illuminated. Fault code for fuel system "Tank Leak" is stored in the [1][2]DME.

Cause:
The fuel cap may be a possible cause of "tank leakage" faults due to:

1. Insufficient sealing pressure: the fuel filler cap is not turned to the full stop.

2. Retaining strap on fuel filler cap is caught between the filler pipe and the fuel filler cap. See Illus.1





An incorrectly sealed fuel filler cap will eventually cause the "CHECK ENGINE" lamp to illuminate. The following fault codes are stored in the [1][2]DME fault memory:

If the values measured during the fuel system check are not reliable, as is the case with the filler pipe open, the fuel tank system is assumed to have a leak. This leads to a fault code, listed, being stored after the first full driving cycle. If another leak is detected after the second full driving cycle, the "CHECK ENGINE" lamp will illuminate.

Refer to the "On Board Diagnostics II" training manual for detailed operation of the evaporative system monitoring and driving cycle parameters.





Illustration 1: The retaining strap (1) can get caught under the fuel filler cap (3), causing the "check engine" lamp to illuminate due to a leak between the cap and the filler neck (2) seal.

Correction:
If the customer has encountered a re-occurring "Tank Leak" fault (due to the retaining strap being caught under the filler cap) remove the retaining strap. The customer must be advised on this situation. Only after consulting with the customer, and getting customer approval, can the retaining strap be removed.

Procedure:
To remove the retaining strap:

1. After performing "Tank Leakage Diagnosis", disconnect the retaining strap from the vehicle body mount by sliding the strap end up and out of the groove.

2. Using a sharp razor blade, trim the strap flush to the filler cap.

Diagnostic Hints: If "tank leakage" faults are stored, check the fuel cap as described below:

1. Inspect the cap for proper sealing. Reinstall the fuel filler cap properly. Make sure the retaining strap is properly positioned.

2. After any maintenance work, repairs or checks on the vehicle fuel system, the following diagnostic hints should be followed:

a. Read out the [1][2]DME fault memory.

b. Check that the fuel filler cap is correctly seated and correct if necessary. When doing this, make sure the retaining strap does not get caught between the cap and the filler neck.

c. If the fault codes ("Tank leakage") are displayed, carry out the function check "Tank leak system check" using the DIS/MoDic.

d. Rectify any other faults which may be stored and clear the fault memory.

e. If the cap is replaced, attach the sticker(s) to the fuel filler cap.





Sticker on the top half of the fuel cap.
(P/N 71 21 1 184 663)





Sticker on the lower half of the fuel cap.
(P/N 71 24 6 750 683)





Between 08/1998 and 1/2000, depending on the model, a newly developed fuel filler cap and filler neck with improved sealing characteristics was introduced. The force required to fully close the cap has been significantly reduced. The sealing effect and the audible "clicking" have been improved. Despite this, the fuel filler cap must always be turned until it has reached the stop point.

Note:
The new fuel filler cap can only fit the updated filler neck. The revised caps are not retrofittable to older style filler necks. Always refer to the EPO when ordering parts.





Parts Information:

Warranty Information:
For information only.