For 1990-2009 cars

### Description

The DTC P0175 Fuel Trim System Rich Bank 2 diagnostic monitors the operation of the air/fuel ratio feedback controls. In order to provide the best possible combination of driveability, fuel economy, and emission control, the powertrain control module (PCM) uses a Closed Loop air/fuel metering system. The PCM monitors the heated oxygen sensor (HO2S) signal voltage and, when in Closed Loop, adjusts the fuel delivery based on the HO2S signal voltage. Changes in fuel delivery will be indicated by the long term and the short term fuel trim values that are displayed on the scan tool. The ideal fuel trim value is around 0 percent. The PCM will add fuel when the heated oxygen sensor signal is indicating a lean condition. Additional fuel is indicated by fuel trim values that are more than 0 percent. The PCM will reduce the amount of fuel delivered when a rich condition is indicated by the HO2S. fuel trim values less than 0 percent indicate a reduction in fuel. A fuel trim DTC can be set when the exhaust emissions reach excessive levels because of a lean or rich condition.

HO2S Indication | Short Term FT Action | Long Term FT Action | Short Term FT Response
--- | --- | --- | ---
Lean Condition | Quick Increase of 1% or More | Slow Increase of 1% or More | Return to 0%
Desired Condition | Stays Near 0% | Stays at Learned +/- Value | Stays Near 0%
Rich Condition | Quick Decrease of -1% or Less | Slow Decrease of -1% or Less | Return to 0%

### Conditions for Running the DTC

• | The barometric pressure (BARO) is more than 75 kPa.

• | The engine coolant temperature (ECT) is between -8°C and +95°C (18°F-203°F) at engine start up.

• | The intake air temperature (IAT) is between -8°C and +60°C (18°F-140°F) at engine start up.

### Conditions for Setting the DTC

Any of the following conditions are detected while the ECT is less than 110°C (230°F):

• | The short term fuel trim of bank 2 is less than or equal to -11 percent in 128 firing events.

• | The long term fuel trim of bank 2 is less than or equal to -11 percent in 128 firing events.

• | The total fuel trim of bank 2 is less than or equal to -30 percent in 128 firing events.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after 3 consecutively passing trips without a fault present.

• | A history DTC will clear after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool Clear DTC Information function in order to clear the DTC.

### Diagnostic Aids

Check for any of the following conditions:

• | If any DTCs other than fuel trim P0171, 1, P0174, P0175, misfire P0300 to P0306 and exhaust gas recirculation (EGR) P0400 are set, diagnose those DTCs first.

• | Check for a restriction in the inlet air passage. A duct or inlet hose that collapses when hot or that is blocked by debris can cause DTC P0175 to set.

• | Check for the correct fuel pressure. The fuel system will be rich if the fuel pressure is too high. In order to determine the cause of DTC P0175 monitoring the fuel pressure while driving the vehicle at various road speeds may be necessary. Refer to Fuel System Diagnosis .

• | A malfunctioning (MAF) sensor.

• | Check for a damaged wiring harness--Inspect the wiring harness for damage. If the harness appears to be OK, observe the HO2S bank 2 sensor 1 display on the scan tool while moving the connectors and the wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.

• | Check for a contaminated oxygen sensor--Silicone and other contaminants can cause the oxygen sensor to provide false exhaust oxygen content readings. If contamination is found, determine the cause and correct the condition before replacing the HO2S.

• | Inspect the HO2S bank 2 sensor 1 for water intrusion into the wiring harness and the sensor housing. Water can create a short to voltage in the HO2S signal circuit causing a false rich indication.

• | Check the HO2S bank 2 sensor 1 and the mass air flow MAF sensor for a faulty electrical connection to the PCM.

If a DTC P0175 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P0175 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0175 appears in the Not Ran Since Code Cleared list, the DTC P0175 diagnostic has not yet run. When the DTC P0175 does not appear in the Not Ran Since Code Cleared list, the DTC P0175 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0175 diagnostic has passed. DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

If a DTC P0175 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The Diagnostic System Check-Engine Controls 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.

2. This step determines if the fault is present.

3. This step checks for excess fuel from the fuel injectors. The fault may be a fuel injector or the fuel injector electrical circuit.

4. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0175 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0175 appears in the Not Ran Since Code Cleared list, the DTC P0175 diagnostic has not yet run. When the DTC P0175 does not appear in the Not Ran Since Code Cleared list, the DTC P0175 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0175 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Start the engine.
2. Allow the engine to reach a normal operating temperature.
3. Operate vehicle until the scan tool indicates Closed Loop.
4. Observe the Short Term FT parameter on the scan tool.

Is the scan tool display more than the specified value?

-11 %

Go to Step 3

Go to Step 4

3 |

1. Turn ON the ignition, leaving the engine OFF.
2. Perform the scan tool Clear DTC Information function.
3. Operate the vehicle within the Freeze Frame conditions as noted.
4. Observe the Total Fuel Trim parameter on the scan tool.

Was the scan tool display more than the specified value while operating the vehicle within the Freeze Frame conditions?

-33 %

Go to Diagnostic Aids

Go to Step 4

4 |

1. Visually/physically inspect the air filter and the air filter assembly for restrictions.
2. Repair as necessary.

Was a repair necessary?

--

Go to Step 10

Go to Step 5

5 |

1. Turn OFF the ignition.
2. Install a J 34730-1A Fuel Pressure Gage or an equivalent. Refer to Fuel Pressure Gage Installation and Removal .
3. Start the engine.
4. Observe the fuel pressure with the engine idling at normal operating temperatures.

Is the fuel pressure within the specified range?

250-300 kPa (36-43 psi)

Go to Step 6

Go to Fuel System Diagnosis

6 |

1. Check the evaporative emission (EVAP) control system for possible over purging of fuel vapors. Refer to Evaporative Emission Control System Diagnosis .
2. Repair any problems found in the EVAP control system.

Was a problem found and repaired?

--

Go to Step 10

Go to Step 7

7 |

1. Remove the HO2S bank 1 sensor 1.
2. Visually inspect the HO2S for damage or contamination.

Important: Repair the cause of the contamination before replacing a contaminated HO2S.

3. Replace the HO2S Bank 1 Sensor 1 if any damage or contamination is evident. Refer to Heated Oxygen Sensor 1 Replacement .

Did the HO2S require replacement?

--

Go to Step 10

Go to Step 8

8 | Check the fuel injectors for any of the following conditions:

• | Verify that the discharge of fuel is regular and even. Refer to Fuel Injector Balance Test with Special Tool .

• | Verify that fuel does not leak from the ball valve of the injector.

• | Verify that the fuel is dispersed in a conical spray pattern.

• | Verify that the electrical resistance of the injector coils are all within specifications. Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) .

Did the fuel injectors pass all the checks?

--

Go to Diagnostic Aids

Go to Step 9

9 | Replace any faulty fuel injectors. Refer to Fuel Injector Replacement . Is the action complete? | -- | Go to Step 10 | --
10 |

1. Turn OFF the ignition.
2. Remove the DOME fuse for 30 seconds.
3. Install the DOME fuse.
4. Reset the radio clock time. Refer to Radio/Audio System Description and Operation in Entertainment.
5. Start the engine.
6. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or until the DTC P0175 diagnostic test has run.

Does the DTC run and pass?

--

Go to Step 11

Go to Step 2

11 | 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