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Home >> Saab >> 1999 >> 9-3 Base, 2D Convertible, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - TRIONIC T5 Fuel Control System >> Diagnostic Tests >> DTC P0121-P0123: Throttle Position Sensor (TPS) Circuit
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DTC P0121-P0123: Throttle Position Sensor (TPS) Circuit

  1. With ignition off, disconnect electrical connector from TPS located on side of throttle body under Idle Air Control (IAC) valve. Turn ignition on. Using DVOM, measure voltage between TPS harness connector terminal No. 1 (White/Black wire) and ground. See Figure . If reading is between 4.5-5.5 volts, go to next step. If voltage is not as specified, repair faulty circuit between TPS harness connector terminal No. 1 and ECM harness connector terminal No. 42 (White/Black wire). ECM is next to glove box on right side. See Figure for ECM terminal identification. Go to step  5 .
  2. Use DVOM to measure voltage between positive battery terminal and TPS harness connector terminal No. 2 (Black wire). If reading is between 11-13 volts, go to next step. If reading is not as specified, repair faulty circuit between TPS harness connector terminal No. 2 and crimped connector J31 located about 2" from ECM harness connector (Black wire). See appropriate wiring diagram in WIRING DIAGRAMS article. Go to step  5 .
  3. Turn ignition off. Connect TECH 2 scan tool to DLC. Turn ignition on. Select READING: THROTTLE POSITION. Scan tool display should be 99 percent. If reading is as specified, go to next step. If reading is not as specified, repair faulty circuit between TPS harness connector terminal No. 3 and ECM harness connector terminal No. 45 (Green/Black wire). Go to step  5 .
  4. Connect a fused jumper wire between TPS harness connector terminals No. 2 (Black wire) and 3 (Green/Black wire). Scan tool display should now read 0 percent. If reading is as specified, replace TPS. See THROTTLE/PEDAL POSITION SENSORS under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION article. If reading is not as specified, repair faulty circuit between TPS harness connector terminal No. 3 and ECM harness connector terminal No. 45 (Green/Black wire). Go to next step.
  5. Use scan tool to clear DTCs. Drive vehicle for 5 minutes under varying loads and engine RPM. Recheck for any stored DTCs. If DTC P0121-P0123 reappears, substitute known good ECM and retest system. See ENGINE CONTROL MODULE (ECM) under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article.
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