TPS SPECIFICATIONS INFORMATION

TPS INFORMATION AND SPECIFICATIONS

1985-88 6000, FIREBIRD, SUNBIRD, Models Affected: FIERO, AND GRAND PRIX MODELS --------------- EQUIPPED WITH 2.8L V6 CPC ENGINES (VIN CODES W, S, 9)

Some 1985-87 Service Manual 6E3 Sections covering the 2.8L V6 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.BL PFI engines (VIN Codes W, S and 9).

When checking TPS output voltage at closed throttle, there are different specifications for the different 2.8L V6 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 on engines (VIN Codes W and S) if the voltage is within the specified range and throttle valve angle reads 0%. The throttle position sensor on the 2.8L (VIN 9) engine is non- adjustable.

ACCEPTABLE CLOSED ADJUSTMENT YEAR MODEL ENGINE/CODE THROTTLE RANGE (VOLTS) SPECIFICATION ---- ----- ----------- ---------------------- ------------- 1985 A/J 2.8L (VIN W) 0.35-0.67 Volts 0.55 +/- 0.1V F 2.8L (VIN S) 0.35-0.67 Volts 0.55 +/- 0.1V P 2.8L (VIN 9) Less than 1.25 Volts Non-Adj. 1986 A/J 2.8L (VIN W) 0.35-0.67 Volts 0.55 +/- 0.1V F 2.8L (VIN S) 0.35-0.67 Volts 0.55 +/- 0.1V P 2.8L (VIN 9) Less than 1.25 Volts Non-Adj. 1987 A/J 2.8L (VIN W) 0.35-0.7 Volts 0.55 +/- 0.1V F 2.8L (VIN S) 0.35-0.67 Volts 0.55 +/- 0.1V P 2.8L (VIN 9) Less than 1.25 Volts Non-Adj. 1988 A/J/W 2.8L (VIN W) 0.35-0.7 Volts 0.55 +/- 0.1V F 2.8L (VIN S) 0.35-0.67 Volts 0.55 +/- 0.1V P 2.8L (VIN 9) Less than 1.25 Volts Non-Adj.

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.