SERVICE MANUAL UPDATE 6E2 DRIVEABILITY AND EMISSIONS

SUBJECT: SERVICE MANUAL UPDATE - SECTION 6E2 - DRIVEABILITY AND EMISSIONS NEW CHART C-1E (PSPS)

VEHICLES AFFECTED: 1989 "B" 4.3L (VIN Z)

The attached Power Steering Pressure Switch (PSPS) Diagnostic Chart C-1E and Facing Page should be added to the 1989 4.3L (VIN Z) "B" Carline Service Manual. This chart should be placed at the end of DRIVEABILITY AND EMISSIONS (SECTION 6E2-C1) as pages 6E2-C1-18 and 6E2-C1-19.

CHART C-1 E POWER STEERING PRESSURE SWITCH (PSPS) 4.3L (VIN Z) "B" CARLINE (TBI)

Circuit Description:

The Power Steering Pressure Switch (PSPS) is normally open to ground, and CKT 495 will be near battery voltage.

Turning the steering wheel increases power steering oil pressure and its load on an idling engine. The pressure switch will close before the load can cause an idle problem.

Closing the switch causes CKT 495 to read less than 1 volt. The ECM will increase the idle air rate and retard the timing.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. Checks for ECM signal voltage on CKT 495 and confirms that ground CKT 450 is OK.

2. Maximum resistance, or infinity, indicates an open switch.

3. Less than 1 ohm indicates that the switch is closed when the power steering pressure is high. Switch is OK.

Diagnostic Aids:

A pressure switch that will not close, or an open CKT 495 or 450, may cause the engine to stop when power steering loads are high.

A switch that will not open, or CKT 495, shorted to ground, will cause timing to retard at idle, and may affect idle quality.

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.