1988 Chevrolet Spectrum ExpressFACTORY OEM SERVICE PROCEDURE

Code 21 (TPS)

  1. Clear code. Start engine and idle for one minute with A/C off. If check engine light is off, problem is intermittent.
  2. If check engine light is on, jumper ALDL and note codes. If code 22 is present, go to appropriate test. If code 21 is present, turn engine off. Remove jumper from ALDL and clear codes.
  3. Disconnect TPS sensor. Start engine and idle with A/C off for one minute or until check engine light comes on. Stop engine. Jumper ALDL and turn ignition on. Note code. If code 21 is present, check that continuity exists between TPS harness connector B13 to Red wire connector at TPS.
  4. With ECM connector installed and ignition on, check that no voltage is present between Red wire at TPS connector and ground. If harness tests bad, repair or replace.
  5. With ECM connector installed and ignition on, probe TPS Green wire connector with a test light to 12 volts. If light is on, TPS or harness connection is faulty. If test light is off, harness from Green wire connector to ECM connector A11 is faulty or bad ECM.
Factory Service Tools

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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.