OIL PRESSURE GAGE READS HIGH (CHANGE OIL PRESSURE SENSOR)

Subject: OIL PRESSURE GAUGE READS HIGH

Model and Year: 1991-92 P TRUCKS (MODEL 32 AND 42) WITH 4.3L (LB4), 5.7L (L05), 7.4L (L19)

Some 1991-1992 P30 (32 and 42) with gasoline engines may show high oil pressure on the dash gauge. This condition is present only on the upper range of the oil pressure gauge (oil pressure will reflect correct readings in the lower and midrange on the scale of the gauge).

This high oil pressure reading may be caused by an incorrect oil pressure sending unit. Some vehicles were built with a 60 lb. sending unit instead of the correct 80 lb. sending unit.

To correct, it will be necessary to inspect the oil pressure sending unit to determine if it is the incorrect sending unit. This can be confirmed by the stamping on the sending unit. The incorrect sending unit (P/N 10068563) is stamped 563. The CORRECT sending unit (P/N 10096178) is stamped 178.

SERVICE PROCEDURE:

Tools Required: J35749 Oil Pressure Sensor Socket or equivalent. Inspection

1. Inspect the side of the sending unit for the stamping number. Note: using a mirror to locate the stamping number may ease the inspection process. 2. If the sending unit is stamped 563, it should be replaced with the correct sending unit (P/N 10096178) using the procedure below.

Replacement of the Sending Unit

1. Disconnect the negative battery cable.

2. Remove the wiring harness connector from the oil pressure sending unit. *5.7L and 4.3L engines-the oil pressure sending unit is located at the left front side of the distributor. *7.4L engines-the oil sending unit is located at the front left side of the block. 3. Remove the oil pressure sending unit using tool J35749 or equivalent. 4. Install the oil pressure sending unit (P/N 10096178) using tool J35749 or equivalent. 5. Connect the wiring harness connector to the oil pressure sending unit. 6. Connect the negative battery cable.

SERVICE PARTS INFORMATION

Part Number Description ------------ ----------------------- 10096178 Oil Pressure Sending Unit (stamped 178)

Parts are currently available from GMSPO

WARRANTY INFORMATION

For vehicles repaired under warranty use: Labor Operation N2220 Use applicable labor time guide for labor hours.

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.