DTC P0138: 1/2 O2S SHORTED TO VOLTAGE Dodge Ram Van B2500

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For circuit identification and wiring diagram, see RAM VAN & RAM WAGON wiring diagram in WIRING DIAGRAMS article.

Note. DTC P0138: 1/2 O2S SHORTED TO VOLTAGE is monitored with engine running for more than 4 minutes and engine coolant temperature at more than 180°F (82.2°C). DTC may be stored in Powertrain Control Module (PCM) when PCM senses that 1/2 Heated Oxygen Sensor (HO2S) voltage is more than 1.5 volts. Possible causes are: defective 1/2 HO2S, defective PCM, defective connectors or defective wiring.

Note. 1/2 HO2S is located in downstream position.

1. Turn ignition on, with engine off. Using scan tool, read DTCs. If DTC SPECIFIC GOOD TRIP COUNTER is displayed and displayed count is "0", go to next step. If DTC SPECIFIC GOOD TRIP COUNTER is not displayed or displayed count is not "0", go to step 4).
2. Turn ignition off. Disconnect 1/2 HO2S connector. Clean and/or repair connector as necessary. Start engine and allow it to idle. Using a voltmeter, check voltage between engine block (ground) and 1/2 HO2S connector, signal circuit (Black/Dark Green wire). If voltage is more than 5.1 volts, go to next step. If voltage is 5.1 volts or less, go to step 6).
3. Ensure 1/2 HO2S connector is still disconnected. Using a voltmeter, check voltage between engine block (ground) and 1/2 HO2S connector, signal circuit (Black/Dark Green wire). Turn ignition off, then on. If voltage is more than 5.1 volts, repair signal circuit for short to voltage with engine off, key on. Perform TEST VER-5A. If voltage is 5.1 volts or less, repair signal circuit for short to voltage with engine running. Perform TEST VER-5A.
4. Ensure ignition is off. Disconnect 1/2 HO2S connector. Clean and/or repair connector as necessary. Using a voltmeter, check voltage between engine block (ground) and 1/2 HO2S connector, signal circuit (Black/Dark Green wire) while wiggling 1/2 HO2S connector and wiring harness between 1/2 HO2S and PCM connector. Start engine and allow it to idle. If voltage is more than 5.1 volts, go to next step. If voltage is 5.1 volts or less, go to step 6).
5. Ensure 1/2 HO2S connector is still disconnected. Using a voltmeter, check voltage between engine block (ground) and 1/2 HO2S connector, signal circuit (Black/Dark Green wire) while wiggling 1/2 HO2S connector and wiring harness between 1/2 HO2S and PCM. Turn ignition off, then on. If voltage is more than 5.1 volts, repair signal circuit for short to voltage with engine off, key on. Perform TEST VER-5A. If voltage is 5.1 volts or less, repair signal circuit for short to voltage with engine running. Perform TEST VER-5A.
6. Turn ignition off. Disconnect 1/2 HO2S connector. Clean and/or repair connector as necessary. Start engine and allow it to idle. Using a voltmeter, check voltage between ground and 1/2 HO2S connector, signal circuit (Black/Dark Green wire). If voltage is more than 4 volts, perform DTC P0141: 1/2 O2 SENSOR HEATER FAILURE test. If voltage is 4 volts or less, go to next step.
7. Turn engine off. Ensure 1/2 HO2S connector is still disconnected. Check for open in signal circuit (Black/Dark Green wire) between 1/2 HO2S connector and PCM connector. If open circuit exists, repair as necessary. Perform TEST VER-5A. If open circuit does not exist, go to next step.
8. Turn ignition off. Ensure 1/2 HO2S connector is still disconnected. Turn ignition on. Using voltmeter connected to engine block (ground), backprobe PCM connector, signal circuit (Black/Dark Green wire). If voltage is more than 4 volts, go to next step. If voltage is 4 volts or less, replace PCM. Perform TEST VER-5A.
9. Ensure 1/2 HO2S connector is still disconnected. Using scan tool, read and record FREEZE FRAME data. Ensure CAUSED BY DTC matches DTC on DTC screen. If DTC matches, go to next step. If DTC does not match, repair DTC using FREEZE FRAME data.
10. Road test vehicle under conditions in FREEZE FRAME data. Using scan tool, read DTCs. If DTC SPECIFIC GOOD TRIP COUNTER is displayed and displayed count is "0", perform DTC P0141: 1/2 O2 SENSOR HEATER FAILURE test. If DTC SPECIFIC GOOD TRIP COUNTER is not displayed or displayed count is not "0", test is complete.