One or more heater & AC (HVAC) temperature and/or air delivery mode door actuator may fail, resulting in improper temperature or air delivery. If this occurs, fault code(s) should be stored in the HVAC control module which should assist in diagnoses.
Problems for specific Cadillac Seville STS years:
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Most reported 1999 Cadillac Seville STS problems
The anti-lock brake system (ABS) control module may fail causing the ABS light to illuminate. Failed modules should be replaced to restore ABS operation.
The trunk pull down switch may fail causing the trunk lid not to close completely. Our technicians tell us that the failed switch can be replaced without changing the complete pull down motor assembly.
The parking brake may not release automatically due to a failed vacuum switch or actuator. Our technicians tell us that if vacuum is supplied to the actuator when the transmission is in gear, the vacuum switch is functioning and replacing the actuator should correct this concern.
The engine may develop an oil leak from the lower crankcase portion of the engine block. Our technicians tell us that the engine must be removed from the vehicle to properly repair this oil leak.
Problems with anti-theft systems using the raised-chip key can prevent the car from starting. The wires in the steering column to the ignition lock cylinder tend to break. The key and ignition lock cylinder should be replaced to correct this condition.
Vehicles equipped with the 4.6L engine may develop excessive oil consumption. Please be advised that under optimum driving conditions, using one quart of oil every 2000 miles is acceptable. This Cadillac standard applies to vehicles with less that 50,000 miles. Our technicians tell us that if you experience excessive oil consumption it may be caused by built up on the piston rings which restricts movement, preventing them from wiping all the oil from the cylinder walls. Oil left behind is then burned during the combustion process. There is a special ring cleaning procedure which can help this situation. The GM service bulletin number is #02-06-01-009C.
An automatic transmission fluid leak may develop from the rubber section of a transmission cooler line. In some cases the rubber section of hose can be replaced. In others, the complete cooler line must be replaced to correct this type of leak.
It is common for the fuel level sensor in the fuel tank read the fuel level incorrectly. The sensor must be replaced to correct the condition. Our technicians recommend having the complete fuel pump module replaced on high mileage vehicles.
The high-pressure power steering lines are known to leak.