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DTC P0123 - THROTTLE POSITION (TP) SENSOR HIGH VOLTAGE INPUT Isuzu Oasis I

Testing & Diagnostics 1 illustration ~482 words
  1. Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral until radiator fan comes on. Turn ignition off. Turn ignition on. Using OBD-II scan tool, check throttle position. If about 10 percent with throttle fully closed and 90 percent with throttle fully opened is not indicated, go to next step. If about 10 percent with throttle fully closed and 90 percent with throttle fully opened is indicated, problem is intermittent. System is okay at this time. Check for poor connections or loose wires at TP sensor and PCM connectors. See WIRING DIAGRAMS article.
  2. Turn ignition off. Disconnect TP sensor 3-pin connector. Turn ignition on. Measure voltage between TP sensor harness 3-pin connector terminals No. 1 (Green/Black wire) and No. 3 (Yellow/Blue wire). see scheme 6 If about 5.0 volts does not exist, go to next step. If about 5.0 volts exists, replace throttle body (TP sensor is not serviced separately).
  3. Using backprobe kit, measure voltage between PCM 31-pin connector "C" terminal C18 (Green/Black wire) and terminal C28 (Yellow/Blue wire). see scheme 3 See WIRING DIAGRAMS article. If about 5.0 volts exists, repair open in Green/Black wire between PCM connector and TP sensor. See WIRING DIAGRAMS article. If about 5.0 volts does not exist, substitute a known-good PCM and recheck. If symptom or indication goes away, replace original PCM.

Scheme 27

Scheme 27: DTC P0131 - PRIMARY HO2S-1 SENSOR LOW VOLTAGE
Scheme 27: DTC P0131 - PRIMARY HO2S-1 SENSOR LOW VOLTAGE
  1. Perform PCM reset procedure. See «TESTS W/CODES - INTRODUCTION»(ref-16345) article. Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral until radiator fan comes on. Road test vehicle with transmission in "2" position (A/T). Using OBD-II scan tool, check HO2S-1 output voltage during acceleration using Wide Open Throttle (WOT). If voltage stays at 0.1 volt or less, go to next step. If voltage does not stay at 0.1 volt or less, problem is intermittent. System is okay at this time. Check for poor connections or loose wires between HO2S-1 connector and PCM connectors. See WIRING DIAGRAMS article.
  2. Check fuel pressure. See FUEL SYSTEM in «BASIC TESTING»(ref-16344) article. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, repair fuel supply system as necessary.
  3. Turn ignition off. Disconnect HO2S-1, 4-pin connector. Start engine and run at idle. Using OBD-II scan tool, check HO2S-1 output voltage. If voltage stays at 0.1 volt or less, go to next step. If output voltage does not stay at 0.1 volt or less, replace HO2S-1.
  4. Turn ignition off. Disconnect PCM 31-pin connector "C". Check for continuity between ground and HO2S-1 harness 4-pin connector terminal No. 2 (White wire). (Scheme 27) If continuity exists, repair short to ground in White wire between PCM 31-pin connector "C" terminal C16 and HO2S-1. If continuity does not exist, substitute a known-good PCM and recheck. If symptom or indication goes away, replace original PCM.

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