For 1990-2009 cars

### System Description

The powertrain control module (PCM) internal circuitry can identify if the vehicle fuel system is capable of supplying adequate amounts of fuel during heavy acceleration, power enrichment (PE). When a power enrichment mode of operation is requested during a Closed Loop operation, by heavy acceleration, the PCM provides additional fuel to the engine. Under these conditions the PCM should detect a rich condition. Whenever this rich exhaust is not detected, DTC P1171 sets.

### Conditions for Running the DTC

• | DTCs P0122, P0123, P0131, P0132, P0133, or P0134 are not set.

• | The engine coolant temperature (ECT) is more than 20°C (70°F).

• | The engine has been running for longer than 20 seconds.

• | The engine is operating in a Closed Loop operation.

• | The engine is in the PE mode.

### Conditions for Setting the DTC

The HO2S 1 voltage is less than 300 mV for 10 seconds.

### Action Taken When the DTC Sets

• | The control module stores the DTC information into memory when the diagnostic runs and fails.

• | The malfunction indicator lamp (MIL) will not illuminate.

• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

• | The driver information center, if equipped, may display a message.

### Conditions for Clearing the DTC

• | 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 non-emission related diagnostic.

• | Clear the DTC with a scan tool.

### Diagnostic Aids

• | A restricted fuel filter can supply adequate amounts of fuel at idle, but may not be able to supply enough fuel during heavy acceleration. Water or alcohol in the fuel may cause low heated oxygen sensor (HO2S) 1 voltage during acceleration.

• | High resistance in the ignition coil control circuits may cause this condition.

• | Manifold absolute pressure (MAP) sensor-High resistance in the MAP sensor circuits may cause this condition.

• | Check for faulty or plugged fuel injectors.

### Test Description

The number below refers to the step number on the diagnostic table.

1. This step checks to see if the HO2S 1 is operating properly.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 | Important: If any other DTCs are set except for HO2S DTCs, refer to the other DTCs first before proceeding with this table.

1. Operate the engine at normal operating temperature.
2. Operate the engine above 1,200 RPM for 2 minutes.
3. With a scan tool, observe the HO2S 1 voltage parameter.

Does the scan tool indicate that the HO2S 1 voltage is varying above and below the specified values?

350-550 mV

Go to Step 3

Go to Step 4

3 |

1. Observe the Freeze Frame/Failure Records data for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, or as close to the Freeze Frame/Failure Records data that you observed.

Does the DTC fail this ignition?

--

Go to Step 4

Go Diagnostic Aids

4 |

1. Check the vehicle for an adequate amount of fuel.
2. Add fuel to the vehicle fuel tank if the fuel gage is near empty.

Was it necessary to add fuel?

--

Go to Step 6

Go to Step 5

5 |

1. Start the engine.
2. Run the engine at normal operating temperature.
3. Operate the engine above 1,200 RPM.
4. With a scan tool, observe the HO2S 1 voltage with the scan tool.

Does the Scan tool indicate HO2S 1 voltage varying outside the specified values?

350-550 mV

Go to Fuel System Diagnosis

Go to DTC P0134

6 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 7

Go to Step 2

7 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK