I have an intermittent check engine light, on my 1991 750iL. I have
the Bentley manual, that describes the connector location as beneath
the transmission. Is there any easier location to check the voltages
to the sensor heaters, and the sensor output?
The check engine light used to come on on the first hill a mile or so
from my house on the morning commute, but now it comes on immediately
upon startup, and sometimes goes out after highway driving.
I used the manual method of reading out stored engine codes (pumping
gas pedal 5 times right after turning on ignition, observing sequence
of flashing 'check engine light'), the output is 1444, which I believe
means everything OK.
I had the vehicle to a dealership before for the check engine light,
and they replaced one of the O2 sensors, upon picking up the car,
there was still a check engine light, but with different behavior, in
terms of when it turns on.
When I returned the car to the dealership, they claimed the check
engine light was due to a slipping transmission. I since had it
serviced, and noticed that the harsh down shifts when coasting 40-45
mph went away, I am unsure whether the slipping transmission engine
code was reset. But the check engine light never went away.
My gas mileage, is 13mpg (US), in a commute with 50% highway, 50%
Are there conditions that cause check engine light to come on, without
storing a code?
Is there indeed a slipping transmission engine code for a 1991 M70, or
is the BMW dealership simply blabbering to cover incompetence?
Any other suggestions for how to troubleshoot this problem?