TPS SPECIFICATIONS INFORMATION

MODELS AFFECTED: 1985-88 BUICKS EQUIPPED WITH LB6 2.8L V-6 ENGINES (VIN CODE W)

Some 1985 through 1987 Service Manual 6E3 Sections covering the 2.8L V-6 PFI engines do not include information on the ability of the ECM to auto-zero throttle position sensor (TPS) reference voltage. Auto-zero can be described as the ability of the ECM to determine a closed throttle position any time TPS voltage is within a specified range (see chart below). As long as the TPS reference voltage is within that range, the system will function properly. This capability is found on all 2.8L PFI engines.

When checking TPS output voltage at closed throttle, there are different specifications for the different 2.8L V-6 applications. "Scan" tools having the ability to also read the throttle valve angle should read 0% when the throttle valve is closed. Do NOT adjust the TPS if the voltage is within the specified range and throttle valve angle reads 0%.

ENGINE/ ACCEPTABLE CLOSED ADJUSTMENT YEAR MODEL CODE THROTTLE RANGE (VOLTS) SPECIFICATION ---- ----- ------- ---------------------- ------------- 1985 Skylark 2.8L (VIN W) 0.35-0.67 Volts 0.55 +/- O.lV 1987 Century 2.8L (VIN W) 0.35-0.7 Volts 0.55 +/- O.lV 1988 Century/ 2.8L (VIN W) 0.35-0.7 Volts 0.55 +/- O.IV Regal

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.