LOW OIL LEVEL MESSAGE OPERATION/DIAG. (NEW PART)

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

MODELS AFFECTED: 1987-1991 ALLANTES

This bulletin is being revised to include additional model years, new diagnostic information for step 3, and new warranty information.

Some 1987-1991 Allantes may exhibit an intermittent false low oil level warning message due to an inoperative oil level sensor.

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 oil level sensor inoperative all the time, 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/Component Location", which follows.

3. Vehicles that have been parked at an angle (ie., on a hill or two wheels in a ditch) either front to back or side to side may exhibit a false low oil message. The angle of the vehicle causes the oil in the oil pan to flow away from the oil level switch. This condition is normal and will not be corrected by replacing the oil level switch or oil pan.

A new sensor, P/N 1649745, has been released. The new sensor requires a new seal which must be ordered separately as P/N 25531045. The seal must be replaced whenever a sensor is replaced. Parts are currently available from GMSPO.

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 BI64. 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 B164 changes to "LO", replace the sensor.

o If the B164 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 B164 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 X/O 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/Component Location:

With proper oil level, the B164 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, B164 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 lever 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 1987/1988 Final Edition Service Information Manual on page 8A-201-0, Figure C.

WARRANTY INFORMATION VEHICLE SERIES Operation Operation Description Number C D E J K V ---------------------------------------------------------------------------- Switch, Engine Oil Level Indicator - N2215 .4 Replace (1991)

Sensor, Engine Oil Level - Replace N4580 .4 (1987-1990)

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.