Diagnostic Trouble Code (DTC) P2177
Fuel Trim System Lean at Cruise or Accel
Circuit Description
The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. During Closed Loop, the HO2S inputs are added and used by the ECM to calculate short and long term fuel trim fuel delivery adjustments. If the HO2S indicate a lean condition, fuel trim values will be above 0 percent. If the O2S indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the HO2S signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the ECM detects an excessively lean condition, this DTC sets.
Conditions for Running the DTC
- Engine load is between 23 and 85 %.
- Air mass flow is between 42 and 350 kg/h.
Conditions for Setting the DTC
- Multipicative value is greater than 1.22.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will be illuminated after 3 valid driving cycles.
- The ECM will record operating conditions at the time the diagnostic fail. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
Conditions for Clearing the MIL/DTC
- The MIL will turn off after three or four consecutive driving cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.
- Disconnecting the ECM battery feed for 10 seconds.
Diagnostic Aids
Important : After repairs, use the scan tool Fuel Trim Reset function to reset the long-term fuel trim to 128 (0%).
- Fuel pressure - The system will be lean if the pressure is too low. It may be necessary to monitor fuel pressure while driving the vehicle at various road speeds and/or loads to confirm.
- MAP sensor - An output that causes the ECM to sense a lower than normal manifold pressure (high vacuum) can cause the system to go lean. Disconnecting the MAP sensor will allow the ECM to substitute a fixed (default) value for the MAP sensor. If the lean condition is gone when the sensor is disconnected, substitute a known good sensor and recheck.
- Fuel contamination - Water, in even small amounts, near the in-tank fuel pump inlet can be delivered to the injector. The water causes a lean exhaust and can set DTC P2177.
Check for poor O2S or MAP sensor connection at the ECM. Inspect the harness connectors for the following conditions:
- Backed-out terminals
- Improper mating
- Broken locks
- Improperly formed
- Damaged terminals
- Poor terminal-to-wire connection
Inspect the wiring harness for damage. If the harness appears to be OK, observe the O2S display on the scan tool while moving the connectors and the wiring harness related to the engine harness. A change in the display will indicate the location of the fault.
Check the brake power booster check valve for possible leaks.
DTC P2177 - Fuel Trim System Lean at Cruise or Accel
| Step | Action | Value(s) | Yes | No |
| 1 | Did you perform the Diagnostic System Check? | - | Go to Step 2 | Go to |
| 2 | - Idle the engine at the normal operating temperature.
- The fuel system is in Closed Loop.
- Observe the Total Fuel Trim Avg. parameter for bank with a scan tool.
Is the Total Fuel Trim Avg. less than the specified value indicated? | - | Go to Step 3 | Go to Step 4 |
| 3 | - Observe the Freeze Frame and/or the Failure records data for this DTC.
- Turn the ignition OFF for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data.
Does the DTC fail this ignition cycle? | - | Go to Step 4 | - |
| 4 | Is bank of the engine operating lean? | - | Go to Step 5 | Go to Step 7 |
| 5 | - Start the engine.
- Disconnect the mass air flow (MAF) sensor harness connector while the engine is operating.
- Observe the Short Term FT parameter for bank with a scan tool.
- Connect the MAF sensor after completing this step.
Does the Short Term FT parameter for both banks of the engine change more than the specified value with the MAF sensor disconnected? | - | - | Go to Step 6 |
| 6 | Inspect for the following conditions: - The vacuum hoses for splits, kinks, and proper connections
- The throttle body and the intake manifold for vacuum leaks
- The crankcase ventilation valve and system for leaks
- The air intake system after the MAF sensor for vacuum leaks
- Contaminated fuel
- Lean injectors
- The engine control grounds for being clean, tight, and in the correct locations
- A high engine oil level condition-A high engine oil level causes oil residue to form on the mass air flow (MAF) sensor, causing a lean indication. The MAF sensor does not need to be replaced.
- An engine mechanical condition
Did you find and correct the condition? | - | Go to Step 8 | - |
| 7 | Inspect for the following conditions: - Vacuum leaks that only affect one bank of the engine--For example, the intake manifold, the injector O-rings.
- Lean injectors
- Exhaust leaks, missing or loose exhaust hardware
- The heated oxygen sensor (HO2S) is installed securely and the electrical connector is not contacting the exhaust system.
- An engine mechanical condition
Did you find and correct the condition? | - | Go to Step 8 | - |
| 8 | - Clear the DTCs with a scan tool.
- Turn OFF the ignition for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Setting the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition? | - | Go to Step 2 | Go to Step 9 |
| 9 | Check if any additional DTCs are set. Are there any DTCs that have not been diagnosed? | - | Go to applicable DTC table | System OK |
Diagnostic Trouble Code (DTC) P2178
Fuel Trim System Rich at Cruise or Accel
Circuit Description
The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. During Closed Loop, the HO2S inputs are added and used by the ECM to calculate short and long term fuel trim fuel delivery adjustments. If the HO2S indicate a lean condition, fuel trim values will be above 0 percent. If the O2S indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the HO2S signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the ECM detects an excessively lean condition, this DTC sets.
Conditions for Running the DTC
- Engine load is between 23 and 85 %.
- Air mass flow is between 42 and 350 kg/h.
Conditions for Setting the DTC
- Multipicative value is less than 0.78.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will be illuminated after 3 valid driving cycles.
- The ECM will record operating conditions at the time the diagnostic fail. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
Conditions for Clearing the MIL/DTC
- The MIL will turn off after three or four consecutive driving cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.
- Disconnecting the ECM battery feed for 10 seconds.
Diagnostic Aids
Important : After repairs, use the scan tool Fuel Trim Reset function to reset the long-term fuel trim to 128 (0%).
Check for poor connection at the ECM. Inspect the harness connectors for the following conditions:
- Backed-out terminals.
- Improper mating.
- Broken locks.
- Improperly formed.
- Damaged terminals.
- Poor terminal-to-wire connection.
Inspect the wiring harness for damage. If the harness appears to be OK, observe the O2S display on the scan tool while moving the connectors and the wiring harness related to the engine harness. A change in the display will indicate the location of the fault.
DTC P2178 - Fuel Trim System Rich at Cruise or Accel
| Step | Action | Value(s) | Yes | No |
| 1 | Did you perform the Diagnostic System Check? | - | Go to Step 2 | Go to |
| 2 | - Idle the engine at the normal operating temperature.
- The fuel system is in Closed Loop.
- Observe the Total Fuel Trim Avg. parameter for bank with a scan tool.
Is the Total Fuel Trim Avg. less than the specified value indicated? | - | Go to Step 3 | Go to Step 4 |
| 3 | - Observe the Freeze Frame and/or the Failure records data for this DTC.
- Turn the ignition OFF for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data.
Does the DTC fail this ignition cycle? | - | Go to Step 4 | - |
| 4 | Is bank of the engine operating lean? | - | Go to Step 5 | Go to Step 7 |
| 5 | - Start the engine.
- Disconnect the mass air flow (MAF) sensor harness connector while the engine is operating.
- Observe the Short Term FT parameter for bank with a scan tool.
- Connect the MAF sensor after completing this step.
Does the Short Term FT parameter for both banks of the engine change more than the specified value with the MAF sensor disconnected? | - | - | Go to Step 6 |
| 6 | Inspect for the following conditions: - The vacuum hoses for splits, kinks, and proper connections
- The throttle body and the intake manifold for vacuum leaks
- The crankcase ventilation valve and system for leaks
- The air intake system after the MAF sensor for vacuum leaks
- Contaminated fuel
- Lean injectors
- The engine control grounds for being clean, tight, and in the correct locations
- A high engine oil level condition-A high engine oil level causes oil residue to form on the mass air flow (MAF) sensor, causing a lean indication. The MAF sensor does not need to be replaced.
- An engine mechanical condition
Did you find and correct the condition? | - | Go to Step 8 | - |
| 7 | Inspect for the following conditions: - Vacuum leaks that only affect one bank of the engine--For example, the intake manifold, the injector O-rings.
- Lean injectors
- Exhaust leaks, missing or loose exhaust hardware
- The heated oxygen sensor (HO2S) is installed securely and the electrical connector is not contacting the exhaust system.
- An engine mechanical condition
Did you find and correct the condition? | - | Go to Step 8 | - |
| 8 | - Clear the DTCs with a scan tool.
- Turn OFF the ignition for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Setting the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition? | - | Go to Step 2 | Go to Step 9 |
| 9 | Check if any additional DTCs are set. Are there any DTCs that have not been diagnosed? | - | Go to applicable DTC table | System OK |
Diagnostic Trouble Code (DTC) P2187
Fuel Trim System Too Lean at Idle
Circuit Description
The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. During Closed Loop, the HO2S inputs are added and used by the ECM to calculate short and long term fuel trim fuel delivery adjustments. If the HO2S indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors (O2S) indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the HO2S signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1.
Conditions for Running the DTC
- Engine speed is less than 1000 rpm.
- Mass air flow is less than 23 kg/h.
Conditions for Setting the DTC
- Addictive value is greater than 8.5.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will be illuminated after 3 valid driving cycles.
- The ECM will record operating conditions at the time the diagnostic fail. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
Conditions for Clearing the MIL/DTC
- The MIL will turn off after three or four consecutive driving cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.
- Disconnecting the ECM battery feed for 10 seconds.
Diagnostic Aids
- A fuel delivery condition causes this DTC to set. Thoroughly inspect all items that cause a lean condition.
- Any un-metered air into the engine causes this DTC to set. Thoroughly inspect all areas of the engine for vacuum leaks.
- For an intermittent condition, refer to "Intermittents".
DTC P2187 - Fuel Trim System Too Lean at Idle
| Step | Action | Value(s) | Yes | No |
| 1 | Did you perform the Diagnostic System Check? | - | Go to Step 2 | Go to |
| 2 | - Idle the engine at the normal operating temperature.
- The fuel system is in Closed Loop.
- Observe the Total Fuel Trim Avg. parameter with a scan tool.
Is the Total Fuel Trim Avg. less than the specified value indicated? | 40% | Go to Step 3 | Go to Step 4 |
| 3 | - Observe the Freeze Frame and/or the Failure records data for this DTC.
- Turn the ignition OFF for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Setting the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data.
Does the DTC fail this ignition cycle? | - | Go to Step 4 | |
| 4 | - Start the engine.
- Disconnect the MAP sensor harness connector while the engine is operating.
- Observe the Short Term FT parameter with a scan tool.
- Connect the MAP sensor after completing this step.
Does the Short Term FT parameter change more than the specified value with the MAP sensor disconnected? | 20% | Go to Step 6 | Go to Step 5 |
| 5 | Inspect for the following conditions: - The vacuum hoses for splits, kinks, and proper connections
- The throttle body and the intake manifold for vacuum leaks
- The crankcase ventilation valve and system for leaks
- Contaminated fuel
- Lean injectors
- The engine control grounds for being clean, tight, and in the correct locations
- An engine mechanical condition
Did you find and correct the condition? | - | Go to Step 6 | |
| 6 | - Turn OFF the ignition for 30 seconds.
- Start the engine.
- Reset the fuel trim system with a scan tool.
- Operate the vehicle within the Conditions for Setting the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition? | - | Go to Step 2 | Go to Step 7 |
| 7 | Is the fuel pressure within the specified value? | - | Go to applicable DTC table | System OK |
Diagnostic Trouble Code (DTC) P2188
Fuel Trim System Too Rich at Idle
Circuit Description
The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. During Closed Loop, the HO2S inputs are added and used by the ECM to calculate short and long term fuel trim fuel delivery adjustments. If the HO2S indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors (O2S) indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the HO2S signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1.
Conditions for Running the DTC
- Engine speed is less than 1000 rpm.
- Mass air flow is less than 23 kg/h.
Conditions for Setting the DTC
- Addictive value is less than -8.5.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will be illuminated after 3 valid driving cycles.
- The ECM will record operating conditions at the time the diagnostic fail. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
Conditions for Clearing the MIL/DTC
- The MIL will turn off after three or four consecutive driving cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.
- Disconnecting the ECM battery feed for 10 seconds.
Diagnostic Aids
- A fuel delivery condition causes this DTC to set. Thoroughly inspect all items that cause a lean condition.
- For an intermittent condition, refer to "Intermittents".
DTC P2188 - Fuel Trim System Too Rich at Idle
| Step | Action | Value(s) | Yes | No |
| 1 | Did you perform the Diagnostic System Check? | - | Go to Step 2 | Go to |
| 2 | - Idle the engine at the normal operating temperature.
- The fuel system is in Closed Loop.
- Observe the Total Fuel Trim Avg. parameter with a scan tool.
Is the Total Fuel Trim Avg. less than the specified value indicated? | -40% | Go to Step 3 | Go to Step 4 |
| 3 | - Observe the Freeze Frame and/or the Failure records data for this DTC.
- Turn the ignition OFF for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Setting the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data.
Does the DTC fail this ignition cycle? | - | Go to Step 4 | |
| 4 | - Start the engine.
- Disconnect the MAP sensor harness connector while the engine is operating.
- Observe the Short Term FT parameter with a scan tool.
- Connect the MAP sensor after completing this step.
Does the Short Term FT parameter change more than the specified value with the MAP sensor disconnected? | 20% | Go to Step 6 | Go to Step 5 |
| 5 | Inspect for the following conditions: - A collapsed air intake duct
- A restricted air filter element
- Excessive fuel in the crankcase - change the oil as necessary.
- Contaminated fuel
- The engine control grounds for being clean, tight, and in the correct locations
- An engine mechanical condition
Did you find and correct the condition? | - | Go to Step 6 | |
| 6 | - Turn OFF the ignition for 30 seconds.
- Start the engine.
- Reset the fuel trim system with a scan tool.
- Operate the vehicle within the Conditions for Setting the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition? | - | Go to Step 2 | Go to Step 7 |
| 7 | Is the fuel pressure within the specified value? | - | Go to applicable DTC table | System OK |
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