SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSPONTIAC1983GRAND PRIX BASE, 5.0 HREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 11 (FEEDBACK CARBURETOR TESTS W/CODES)CODE 21: TPS CIRCUIT HIGH
1983 Pontiac Grand Prix Base, 5.0 H

Code 21: TPS Circuit High

1983 Pontiac Grand Prix Base, 5.0 HSECTION Code 21: TPS Circuit High
WARNING: This page does not describe the selected car, but rather 28 other vehicles, including the 1984 Pontiac Phoenix, 1984 Pontiac Parisienne, 1984 Pontiac Grand Prix, 1984 Pontiac Firebird, and 1984 Pontiac Bonneville. However, it is still accessible from the selected car via links, so may be relevant.

Code 21 means that the ECM has seen a high TPS voltage for more than about 10 seconds, below a specified RPM or below a specified engine load. Due to the pull-up resistor between terms. 21" and "2" within the ECM, an open in the TPS circuit will place about 5 volts (high TPS signal) at term. "2" of ECM.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).
  1. This test checks the circuits from the TPS connector back to the ECM. Both wires should read about 5 volts due to the pull-up resistor in the ECM.
    NOTE: A 10 Megohm resistance meter must be used. A lower resistance voltmeter would read virtually zero at term. "B".
  2. This test checks if low voltage at TPS connector is an open in the circuit or a faulty ECM. A normal reading at the ECM is about 5 volts.
  3. This test simulates closed throttle. Dwell should increase if the ECM is good.
  4. This tests the resistance of the TPS switch. Normal reading is less than 20,000 ohms.
Fig 1: Code 21: TPS Circuit High Flow Chart
G201246
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.