LOW OIL LEVEL MESSAGE OPERATION/DIAGNOSIS & NEW PART

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

MODELS/YEARS 1988-90 TORONADO AND TROFEO

Some 1988-1990 Toronados and Trofeos may exhibit an intermittent false low oil level warning message due to either 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 on cars with 3800 (LN3) VIN C engines. The new pan requires a new gasket, oil pump screen, oil pump screen gasket, and dipstick. These parts can be ordered through GMSPO 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 B188. If the input is "HI", go to 4A. If the input 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 B188 changes to "LO":

- For 1988 Toronado's/Trofeo's; replace the sensor.

- 1989-1990 Toronado's/Trofeo's; replace the oil pan, oil pump screen, dipstick, and sensor.

o If the B188 changes remain "HI" with the terminals jumpered, check for an open in circuit 1 1 4 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 B188 while moving the 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 X/O status indicator will change from 0 to X ff 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 B188 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, B188 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 15C (59F) or more since the last engine run cycle. Example: If the engine was running at 90C (194F) coolant temp at key "OFF" and is at 85C (185F) coolant temp at key "ON", the BCM will ignore oil level sensor input. If the engine is at 90C (194F) at key "OFF" and is at 25C (77F) 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 1990 Toronado/Trofeo Service Manual on page 8A-201 -0, Figure A.

For oil pan replacement procedure, refer to Section 6A8 in the 1990 Toronado/Trofeo Service Manual. Torque engine oil pan bolts to 1 0 N.m (7 lbs. ft.), then retorque to 16 N.m (1 2 lbs. ft.).

WARRANTY INFORMATION:

Operation Labor Trouble Operation Description Number Time Code --------------------- --------- ----- ------- 1988 Sensor, Engine Oil Level - Replace N2215 * 92

1989-1990 Low Oil Level Message - Replace Oil Pan, T6467 0.8 hour 92 Gasket, Oil Pump Screen, Dipstick, and Oil Level Sensor

*See current Labor Time Guide.

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.