Test TC-9A - 02S Stays At Center (DTC 21)

WARNING: This page is about a different car, the 1995 Plymouth Voyager, 1995 Plymouth Grand Voyager, 1995 Dodge Grand Caravan, 1995 Dodge Caravan, and 1995 Chrysler Town & Country. 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 . For wiring diagrams, see WIRING DIAGRAMS section at the end of this article.

Start engine. Allow engine to run until normal operating temperature is reached. Using scan tool, set engine speed to 1500 RPM. Using scan tool, read Oxygen Sensor (O2S) state. If O2S is not switching from rich to lean, go to step 4). If O2S is switching from rich to lean, wiggle sensor connector and wiring harness while watching scan tool display.
If O2S is locked at center at any time, inspect all related wiring and connectors, and repair as necessary. Perform TEST VER-2. If O2S is not locked at center at any time, condition required to set DTC is not present at this time. O2S STAYS AT CENTER DTC sets if O2S 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 O2S circuit or O2S failure. Go to next step.
Inspect all related wiring and connectors, and repair as necessary. Perform TEST VER-2. If no problems are found with wiring and connectors, see INACTIVE DTC CONDITION . Perform TEST VER-2.
Turn ignition off. Disconnect O2S connector. Turn ignition on. Using scan tool in ohmmeter mode, check resistance of ground circuit (Black/Light Blue wire) at O2S connector harness side. If resistance is more than 5 ohms, repair open Black/Light Blue wire. Perform TEST VER-2.
If resistance is less than 5 ohms, connect a jumper wire between O2S signal circuit (Dark Green/White wire) and battery positive terminal. Using scan tool, read O2S voltage. If voltage is more than one volt, replace O2S. Perform TEST VER-2.
If voltage is less than one volt, turn ignition off. Disconnect Powertrain Control Module (PCM) connector. Disconnect jumper wire between O2S signal circuit (Dark Green/White wire) and battery positive terminal.
Using an external ohmmeter, check resistance of signal circuit (Dark Green/White wire) between O2S 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 Dark Green/White wire. Perform TEST VER-2.