Schematic Reference: Engine Controls Schematics
Circuit Description
Heated oxygen sensors are used to minimize the amount of time before closed loop fuel control operation and to allow accurate catalyst monitoring. The oxygen sensor heater is required by catalyst monitor sensor HO2S 2 to maintain a sufficiently high temperature. This allows accurate exhaust oxygen content readings further from the engine.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
| • | HO2S heater current exceeds 2 amps. |
| • | HO2S heater current is 0.2 amps or less. |
Action Taken When the DTC Sets
| • | The PCM illuminates the MIL during the second key cycle in which the DTC sets. |
| • | The PCM stores the conditions which were present when the DTC set as Freeze Frame Data. |
| • | The PCM turns the HO2S 2 heater OFF. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present. |
| • | A DTC clears after 40 consecutive warm-up cycles have occurred without a fault. |
| • | A DTC can be cleared by using the scan tool Clear DTC Information function. |
Diagnostic Aids
Check the following conditions:
Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the HO2S 2 display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the HO2S 2 display will indicate the location of the fault.
An intermittent malfunction may be caused by fault in the HO2S circuit sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals. |
| • | Improper mating of terminals. |
| • | Broken electrical connectors locks. |
| • | Improperly formed or damaged terminals |
| • | Faulty terminal to wire connections. |
| • | Physical damage to the wiring harness. |
| • | A broken wire inside the insulation. |
| • | Corrosion of electrical connections, splices, or terminals. |
Repair any electrical circuit faults that were found. Refer to Wiring Repairs in Wiring Systems .
The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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This step verifies whether the malfunction is a hard failure or an intermittence.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to OBD System Check | |
2 |
Does the DTC P0141 set? | -- | Go to Diagnostic Aids | |
3 |
Does the test lamp illuminate? | -- | ||
4 |
Does the test lamp illuminate? | -- | ||
5 | Start and idle the engine. Does the test lamp illuminate? | -- | ||
6 |
Was a repair necessary? | -- | ||
7 |
Was a repair necessary? | -- | ||
8 |
Is the action complete? | -- | -- | |
9 |
Was a repair necessary? | -- | ||
10 | Replace the HO2S 2. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | -- | |
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |
12 |
Are any DTCs displayed on scan tool? | -- | Go to the applicable DTC table | System OK |
