Circuit Description
The heated oxygen sensor (HO2S) 2, located in the exhaust stream past the 3-way catalytic converter (TWC), produces an output signal relative to the oxygen storage capacity of the catalytic converter. The powertrain control module (PCM) can then determine the ability of the TWC to convert the exhaust emissions effectively. The HO2S 2 signal will be far less active than the signal produced by the front oxygen sensor 1 (O2S 1).
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0172, P0201-P0204, P0300, P0301-P0304, P0336, P0440, P0446, P0452, P0453, P0506, P0507, P0601, P0602, or P1441 are not set. |
| • | The engine coolant temperature (ECT) is more than 70°C (158°F). |
| • | The engine run time is more than 10 seconds. |
| • | The throttle position (TP) angle is between 8-50 percent for 4 seconds. |
| • | The above conditions are met for 3.8 seconds. |
| • | Closed Loop operation. |
| • | The system voltage more than 10 volts. |
| • | The fuel level more than 10 percent . |
| • | The fuel ethanol composition less than 88 percent. |
| • | The manifold absolute pressure (MAP) is greater than 25 kPa. |
Conditions For Setting The DTC
The HO2S 2 remains below 43 mV for 150 seconds.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
Important: Never solder the HO2S wires. For proper wire and connector repair refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Use the scan tool in order to observe the long term FT values at the different RPM and the air flow conditions. The scan tool also displays the fuel trim cells, so the long term FT values can be checked in each of the cells in order to determine when the DTC may have set. If the conditions for this DTC exist, the long term FT values measure around 158 or more.
Inspect for the following conditions:
| • | A sensor pigtail may be mispositioned and contacting the exhaust manifold. |
| • | An intermittent ground in wire between the connector and the sensor. |
| • | A poor PCM ground |
| • | Lean injectors--Perform the Injector Balance Test. Refer to Fuel Injector Balance Test with Tech 2 or Fuel Injector Balance Test with Special Tool . |
| • | Fuel Contamination--Water, even in small amounts, near the in-tank fuel pump inlet can be delivered to the injectors. The water causes a lean exhaust and can also set this DTC. |
| • | Fuel pressure--If the pressure is too low, the system will be lean. In order to confirm, monitor a fuel pressure gauge while driving the vehicle at various speeds and loads. Refer to Fuel System Diagnosis . |
| • | Exhaust leaks--If there is an exhaust leak, the engine may pull the outside air into the exhaust and past the sensor. Refer to Exhaust Leakage in Engine Exhaust. |
| • | Vacuum or crankcase ventilation system leaks can cause a lean condition or possibly a high idle. |
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step determines if DTC P0137 is the result of a hard malfunction or an intermittent condition.
-
It is necessary to jump the HO2S 2 low signal circuit to ground in order to allow the PCM to display the supplied bias voltage. The PCM and the wiring are OK if the voltage is between 350-550 mV.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
Does the HO2S 2 voltage measure less than the specified value? | 200 mV | Go to Step 4 | Go to Step 3 | |||||||
3 |
Does the HO2S 2 voltage measure less than the specified value? | 40 mV | Go to Step 4 | Go to Diagnostic Aids | ||||||
Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Does the scan tool indicate the HO2S 2 voltage within the specified value? | 350-550 mV | Go to Step 7 | Go to Step 5 | |||||||
5 |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 | ||||||
6 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- | ||||||
7 |
Did you complete the replacement? | -- | Go to Step 8 | -- | ||||||
8 |
Does the DTC run and pass? | -- | Go to Step 9 | Go to Step 2 | ||||||
9 | With a scan tool, observe the stored information in Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||
