LOW OIL LEVEL MESSAGE OPERATION-NEW SENSOR RELEASED

SUBJECT: LOW OIL LEVEL MESSAGE OPERATION (DIAGNOSIS AND NEW OIL LEVEL SENSOR SERVICE PART RELEASED)

VEHICLES AFFECTED: 1987-89 V, 1988-90 E

This Bulletin has been revised to include additional part release/ procedure information and explain the models involved when replacing the sensor or oil pan in Step 4A.

Some 1987-1990 Allantes, 1988-1990 Rivieras/Reattas, or 1989-90 Toronados/Trofeos may exhibit an intermittent false low oil level warning message due to an inoperative oil level sensor or a misformed oil pan.

Important: ----------

1. Some customers may confuse oil pressure warnings with low oil level messages. It is critical to identify which oil warning message (pressure or level) was displayed before attempting to repair an oil warning condition.

2. With either an oil level sensor inoperative all the time, or a misformed oil pan, the message will appear to be intermittent because of the way that the oil level is tested by the body computer. See "Oil Level Sensor System Operation", which follows.

A new sensor, P/N #1649745, has been released. The new sensor requires a gasket or seal which must be ordered separately as P/N #25531045. The seal must be replaced whenever a sensor is replaced.

A new oil pan has been released for service and 1990 Production on cars with 3800 engines built on or after July 2, 1990. The engine. build date can be found on a sticker on the rear valve cover and can be viewed by looking past. the brake master cylinder from the driver's side of the car.

The new pan requires a new gasket, oil pump screen, oil pump screen gasket, and dipstick. These parts can be ordered as a kit using P/N #12350269.

To Diagnose Low Oil Level Messages:

1. Check the oil level using the dipstick.

2. Turn the key to on with the engine off. If the engine has been running, allow time for the oil to drain back into the oil pan.

3. Enter service diagnostics and monitor BCM Input BI88 (Buick and Olds), BI64 (Allante). If the input is "HI". go to 4A. If the output is "LO", go to 4B.

4A. If value reads "HI" with oil level OK, disconnect the oil level sensor connector and jumper the harness terminals together,

o If the BI88/BI64 change to "LO":

- All model Allantes and 1988 Rivieras/Reattas and Toronados; replace the sensor.

- 1988-1990 Rivieras/Reattas and Toronados with engines built before July 2, 1990; replace the oil pan, oil pump screen, dipstick, and sensor.

o If the BI88/BI64 changes remain "HI" with the terminals jumpered, check for an open in circuit 114 from the BCM to the sensor; and check the sensor ground circuit for continuity to ground. Repair any wiring faults found and reconnect the sensor. (Go back to step 3).

4B. If value reads "LO" with oil level OK (possible intermittent sensor or wiring).

o In Diagnostics, monitor BI88/BI64 while cycling wiring and connectors between the oil level sensor and the BCM. Any open circuit between the sensor and BCM or between the sensor and ground will cause the oil level input to be "HI" and could cause a false low oil level message. The XIO status indicator will change from 0 to X if an open occurs.

IMPORTANT: Due to oil splash the sensor input will change from low to high while driving. This is a normal condition. Perform tests for intermittent sensors at key on, engine off.

Oil Level Sensor System Operation:

With proper oil level, the BI88/BI64 should be "LO". (The sensor grounds the 5 Volt circuit from the BCM when oil level is OK; a ground on the circuit is "LO" in diagnostics.)

If oil level is low, BI88/BI64 should be "HI". (The sensor is open with low oil level and the BCM 5 Volt circuit remains at 5 Volts; "HI" in diagnostics.)

The BCM only checks oil level at key on when the engine has cooled by 15(C or more since the last engine run cycle. Example: If the engine was running at 90'C coolant temp at key off and is at 85'C coolant temp at key on, the BCM will ignore oil level sensor input. If the engine is at 90'C at key off and is at 25'C at key on, the BCM will check the sensor status. If the status is "HI' or open, the BCM will display a low oil level warning.

The Oil Level Sensor component location for all model years is shown in (the 1988 F'inal Edition Service Manual on page 8A-201-2 Figure A - OLDS), (the 1988 Final Edition Service Manual on page 8A-201-3 Figure B - BUICK), (the 1987/1988 Final Edition Service Manual on page 8A-201-0 Figure C - ALLANTE).

For oil pan replacement procedure, refer to Section 6A8 in the Service Information Manual. Do not follow oil pan torque specification in Service Manual. Torque engine oil pan bolts to 10 N-m (7 ft.lbs.), then retorque to 16 N-m (12 ft.lbs.).

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.