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Home >> Jeep >> 1996 >> Grand Cherokee Limited, 5.2 Y >> Repair and Diagnosis >> External Pages >> Different car >> Section 3 (Engine Controls - Tests W/Codes - 2.5L Flex Fuel) >> Self-Diagnostic Tests >> Test TC-7A - O2S Stays At Center (DTC 21)

Test TC-7A - O2S Stays At Center (DTC 21)

WARNING: This page is about a different car, the 1994 Plymouth Acclaim and 1994 Dodge Spirit. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: For circuit and connector terminal identification, see CONNECTOR IDENTIFICATION DIRECTORY TABLE  . For wiring diagrams, see WIRING DIAGRAMS  .
  1. Start engine. Allow engine to run until normal operating temperature is reached. Using DRB, set engine speed to 1500 RPM. Using DRB, read oxygen sensor state. If oxygen sensor is locked at center, go to step 4). If oxygen sensor is not locked at center, wiggle oxygen sensor connector and wiring harness while watching DRB display.
  2. If oxygen sensor was locked at center at any time, inspect all related wiring and connectors and repair as necessary. Perform TEST VER-2  . If oxygen sensor was not locked at center at any time, condition required to set trouble code is not present at this time. The O2S STAYS AT CENTER trouble code sets if oxygen sensor output voltage stays at .5 volt for 1.5 minutes with engine temperature more than 170°F (77°C) and engine running for 2 minutes. Possible causes are: open oxygen sensor circuit or oxygen sensor failure. Go to next step.
  3. Inspect all related wiring and connectors and repair as necessary. Perform TEST VER-2. If no problems were found with wiring and connectors, see INACTIVE TROUBLE CODE CONDITION  . Perform TEST VER-2.
  4. Disconnect oxygen sensor connector. Put DRB in ohmmeter mode. Using DRB, check resistance of Black/Light Blue wire at oxygen sensor connector harness side. If resistance is more than 5 ohms, repair open in Black/Light Blue wire. Perform TEST VER-2.
  5. If resistance is less than 5 ohms, connect a jumper wire between oxygen sensor Black/Dark Green wire (Dark Green/White on Dakota) and battery positive terminal. Using DRB, read oxygen sensor voltage. If voltage is more than one volt, replace oxygen sensor. Perform TEST VER-2  .
  6. If oxygen sensor voltage is less than one volt, turn ignition off. Disconnect Powertrain Control Module (PCM) connector. Disconnect jumper wire between oxygen sensor Black/Dark Green wire (Dark Green/White wire on Dakota) and battery positive terminal.
  7. Using an external ohmmeter, check resistance of oxygen sensor Black/Dark Green wire (Dark Green/White wire on Dakota) between oxygen sensor connector harness side and PCM connector terminal No. 41. If resistance is less than 5 ohms, replace PCM. Perform TEST VER-2. If resistance is more than 5 ohms, repair open in Black/Dark Green wire (Dark Green/White wire on Dakota). Perform TEST VER-2.
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