Circuit Description
In order to control emissions, a 3-way catalytic converter (TWC) converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.
The powertrain control module (PCM) has the capability to monitor this process by using a rear heated oxygen sensor (HO2S) 2. The HO2S 2 , located in the exhaust stream past the TWC, produces an output signal which indicates the storage capacity of the catalyst. This in turn indicates the catalysts ability to convert the exhaust emissions effectively. If the catalyst is functioning properly, the HO2S 2 signal will be far less active than the signal produced by the front oxygen sensor (O2S) 1.
Replace the entire HO2S 2 assembly. DO NOT attempt to repair the HO2S 2 if the following conditions exist:
| • | Damaged wiring |
| • | Damaged electrical connectors |
| • | Damaged terminals |
Obstruction of the air reference and degraded HO2S 2 performance could result from any attempt to repair the above conditions.
The HO2S 2 must have a clean air reference in order for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0169, P0171, P0172, P0201-P0204, P0300, P0301-P0304, P0336, P0440, P0446, P0452, P0453, P0506, P0507, P0601, P0602, or P1441 are not set. |
| • | The engine is in Power Enrichment Mode. |
| • | The engine is in Closed Loop. |
| • | The fuel level is more than 10 percent. |
| • | The fuel ethanol composition is less than 88 percent. |
Conditions For Setting The DTC
The O2S 1 is more than 700 mV and the HO2S 2 is less than 399 mV for 9.5 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
| • | The exhaust system--Inspect the exhaust system for the following conditions: |
| - | Exhaust system leaks between the TWC and the flange |
| - | Exhaust system corrosion between the TWC and the flange |
| - | Exhaust system loose or missing hardware between the TWC and the flange |
| - | Repair the conditions as necessary. |
| • | A poor electrical connection or a damaged harness--Inspect the harness for a short to ground in the HO2S 2 high signal circuit. Ensure that the HO2S 2 pigtail is not contacting the exhaust. |
| Check for the following conditions: |
| - | Wiring contacting the exhaust system |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed harness connectors |
| - | Damaged terminals |
| - | Poor terminal-to-wire connections |
| - | A damaged harness |
| • | Intermittent test--Observe the HO2S 2 on the scan tool while moving any of the related electrical connectors and the wiring harness with the ignition ON. If the malfunction is induced, the HO2S 2 display will change. This should help isolate the location of the malfunction. |
An intermittent could be the result of the following conditions:
| • | A poor electrical connection |
| • | Rubbed-through wire insulation |
| • | A broken wire inside of the insulation |
Replace the entire HO2S 2 assembly. DO NOT attempt to repair the HO2S 2 if the following conditions exist:
| • | Damaged wiring |
| • | Damaged electrical connectors |
| • | Damaged terminals |
Obstruction of the air reference and degraded HO2S 2 performance could result from any attempt to repair the above conditions.
The HO2S 2 must have a clean air reference in order for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if DTC P1137 is the result of a hard malfunction or an intermittent condition.
-
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 0.35-0.55 volts.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||
2 |
Are any DTC codes set? | -- | Go to Step 3 | |||||
Check the HO2S 2 voltage with the scan tool. Is the HO2S 2 voltage less than the specified value? | 200 mV | Go to Step 5 | Go to Step 4 | |||||
4 |
Does the HO2S 2 voltage measure less than the specified value? | 399 mV | Go to Step 5 | Go to Step 9 | ||||
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 is within the specified value? | 350-550 mV | Go to Step 8 | Go to Step 6 | |||||
6 |
Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 7 | ||||
7 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- | ||||
8 |
Did you complete the replacement? | -- | Go to Step 9 | -- | ||||
9 |
Does the DTC run and pass? | -- | Go to Step 10 | Go to Step 2 | ||||
10 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
