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DTC P0131: 1/1 O2 Sensor Shorted To Ground: Testing

NOTE: 1/1 HO2S may also be referred to as an upstream oxygen sensor. On 2.4L, 1/1 HO2S is located on exhaust manifold flange. On 3.3L and 3.8L, 1/1 HO2S is located on right exhaust manifold flange (manifold closest to firewall).
  1. Start engine and allow it to idle. Using scan tool, read 1/1 HO2S voltage. If voltage is less than .08 volt, go to next step. If voltage is .08 volt or more, go to step  7.
  2. Turn ignition off. Disconnect 1/1 HO2S connector. Start engine and allow it to idle. Using scan tool, read 1/1 HO2S voltage. If voltage is .08 volt or less, go to next step. If voltage is more than .08 volt, replace 1/1 HO2S.
  3. Turn ignition off. Ensure 1/1 HO2S is still disconnected. Disconnect PCM connectors. PCM is located on left side of engine compartment, near front of battery. Measure resistance between ground and Dark Blue/Light Blue wire at 1/1 HO2S harness connector. If resistance is 100 ohms or more, go to next step. If resistance is less than 100 ohms, repair short to ground in Dark Blue/Light Blue wire between PCM and 1/1 HO2S.
  4. Measure resistance between Dark Blue/Light Blue and Brown/Dark Green wires at 1/1 HO2S harness connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, Dark Blue/Light Blue and Brown/Dark Green wires are shorted together. Repair wiring as necessary.
  5. Measure resistance between Dark Blue/Light Blue and Brown/Light Green wires at 1/1 HO2S harness connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, Dark Blue/Light Blue and Brown/Light Green wires are shorted together. Repair wiring as necessary.
  6. At this time, PCM is assumed to be defective. Replace PCM. Program the new PCM. See PROGRAMMING .
  7. At this time, conditions for DTC to set do not exist or fault is an intermittent problem. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Using scan tool, monitor parameters related to DTC while wiggling connectors and wiring harness. If value changes while wiggling connectors and wiring harness, repair connectors and wiring harness where wiggling caused value to change. If value does not change, review Freeze Frame data using scan tool. Attempt to duplicate condition that caused DTC to set. Check for any related technical service bulletins that may apply. Visually inspect related connectors and wiring harness. Repair connectors and wiring harness as necessary. See WIRING DIAGRAMS article. If no problems are indicated, test is complete.
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