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Discussion Starter #1
The check engine light came on in my 1987 Eldorado. This has not happened in many years. The reading I got on the display said ARE which didn't mean anything to me so I took it to a shop that specializes in older GM cars and who has repaired this car for years . His diagnosis was a problem with the O2 sensor and the engine ECU. Since the check engine light came on the engine has actually been running smoother than ever before. The light comes on and goes off intermittently but the engine function seems to be fine. Is there anyone who repairs the engine ECU? Should I replace the oxygen sensor? I just spent $1000 on a new headliner and taking some scratches out of the paint so the car looks as if it just came out of the showroom inside and out
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so I hate to give up on it especially when it is also running really quietly and smoothly. What to do?
 

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White Diamond '03 DHS (with DTS floor shift)
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O2 sensors are cheap and easy to replace. I'd start with that. ECU's are generally pretty reliable.
 

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70 Deville 78 Seville 92 Deville 03 Deville
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That car looks nice. I wouldn't worry about the engine light unless it started running bad. Is the catalytic converter original? If so, it is due for problems sometime.
 

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92 Fleetwood 2dr cpe - FWD, 96 Seville SLS, 02 Seville
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If the o2 sensor readings are bad, the ECU will revert back to open loop, and run differently.
 

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Discussion Starter #5
Thanks all for your suggestions. I believe that the catalytic converter is original. I don't remember if I've changed the o2 sensor, but probably not. I'll get a new one. I've owned it for 8 years and have 89,000 miles on the odometer. I change the oil myself regularly, have all other fluids changed and tune up
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professionally. Maybe the ECU has reverted to open loop and that's why it is running so very smoothly if it isn't listening to information from a bad 02 sensor. Is the o2 sensor something readily available form Advanced Auto or a normal auto supply shop?
 

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92 Fleetwood 2dr cpe - FWD, 96 Seville SLS, 02 Seville
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Run the car in diagnostic mode and monitor loop status as well as o2 sensors/fuel trim. From my 92 Fleetwood FSM:

To enter the diagnostics system, simultaneously press and hold the OFF and WARMER buttons with the engine running until the system activates. Any diagnostic codes will display first. When the system prompts you with .7.0 you want to press the LO button. This will force the sytem to the PCM data mode and the display will show E.9.0 Use the HI and LO buttons to scroll thru the PCM data parameters. Here is what you can access....

P01 throttle position in degrees
P02 MAP (manifold absolute pressure) in kPa
P03 computed barometer in kPa. Subtract MAP from BARO to get engine vacuum
P04 coolant temperature in degrees C
P05 MAT (manifold air temperature) in degrees C
P06 spark advance
P07 battery voltage
P08 engine RPM....tach
P09 vehicle speed MPH

P12 injector pulse width
P14 oxygen sensor voltage
P16 oxygen sensor cross counts...a measure of O2 sensor activity
P18 closed loop integrator (128 ideal...less equals leaning, more enriching)
P20 closed loop block learn value (same as above)



When driving with the diagnostics activated the icons on the climate control panel stand for other functions....kind of like tell tales on an instrument cluster....

rear defog is the VCC status
front defrost is 4 gear status
ECON is the o2 sensor status (on is rich)
AUTO is the closed loop status
OFF is the closed throttle switch status
OUTSIDE TEMP is the AC compressor request
F is the AC low pressure switch status
C is the heater water valve status
AUTO FAN is the cooling fan command status
 

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70 Deville 78 Seville 92 Deville 03 Deville
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It doesn't sound like a catalytic since it smooths out with the light on. I am a sucker for white leather seats, love your car.
 
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