Check Engine Light Won't Go Out

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Maxwire - 10 Nov 2005 20:53 GMT

I have a 99 M3 (E36), and the check engine light won't go away. The BMW
dealer has replaced the oxygen sensor, gas cap, and done a tune-up on one
visit. The light came back on in a few days. After that the computer was
reset, but again the light came on in a few days. I got the following info
from the dealer:

I PULLED THE FILE ON YOUR CAR. IT HAD 254 TIMES BETWEEN VISITS A MAJOR TANK
LEAKAGE DECTION. THE DME HELD CODE P0144 WHICH IS A MAJOR TANK LEAKAGE
FAULT, NORMALLY EITHER A GAS CAP IS LEAKING OR THE CAR WAS FILLED UP WHILE
RUNNING..........

I never fill up my car while it is running, and I always tighten the cap as
far as possible. Another mechanic has also thoroughly gone over the gas
tank and fuel system, and found nothing.

Any ideas on where to go next?

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Kyle and Lori Greene - 10 Nov 2005 22:56 GMT

>I have a 99 M3 (E36), and the check engine light won't go away. The BMW
>dealer has replaced the oxygen sensor, gas cap, and done a tune-up on one
[quoted text clipped - 12 lines]
>
> Any ideas on where to go next?

If you brought it to a BMW dealer, they should have checked the fuel system
for leaks by attaching some sensors to the tank purge valve and the gas
filler hole using the GT1 or MoDic computers in the shop. The TIS has the
procedure under section 16 00 100 Checking fuel tank and tank ventilation
system for leak-tightness.

There are several fittings around the tank that can crack causing this code.
The dealer should be able to narrow down whether you have a leak or a bad
sensor.

Kyle.
98 740iL
01 525i

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Jeff Strickland - 11 Nov 2005 23:11 GMT

>I have a 99 M3 (E36), and the check engine light won't go away. The BMW
>dealer has replaced the oxygen sensor, gas cap, and done a tune-up on one
[quoted text clipped - 6 lines]
> LEAKAGE FAULT, NORMALLY EITHER A GAS CAP IS LEAKING OR THE CAR WAS FILLED
> UP WHILE RUNNING..........

I'm not sure what a P0144 means, but a gas cap throws a P0440, or another in
that range.

The gas cap is part of the Evaporative Emissions Control System, and all
codes for this system fall within the range of P0440 to P0459 -- maybe
P0460.

> I never fill up my car while it is running, and I always tighten the cap
> as far as possible. Another mechanic has also thoroughly gone over the
> gas tank and fuel system, and found nothing.
>
> Any ideas on where to go next?

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Gcracker - 12 Nov 2005 15:07 GMT

Not true! DTC Code p0144 involves the oxygen sensor, not the fuel tank or
evap system.

read: "O2 Sensor Circuit High Voltage (Bank 1 Sensor 3)"

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Kyle and Lori Greene - 12 Nov 2005 16:00 GMT

> Not true! DTC Code p0144 involves the oxygen sensor, not the fuel tank or
> evap system.
>
> read: "O2 Sensor Circuit High Voltage (Bank 1 Sensor 3)"

That tells me that you have the wrong code. BMW's only have 2 sensors per
bank, not 3.

Kyle.
98 740iL
01 525i

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