Diagnostic Instructions
DTC Descriptors
DTC P2178 : Fuel Trim System Rich at Cruise or Accel
DTC P2188 : Fuel Trim System Rich at Idle
DTC P2192 : Fuel Trim System Rich at Higher Load
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.
Conditions for Running the DTC
P2178
• | The engine load is between 27-85 percent. |
• | The fuel system is in closed loop. |
• | The engine coolant temperature (ECT) is greater than 70°C (158°F). |
• | The intake air temperature (IAT) is less than 80°C (176°F). |
• | The evaporative emission (EVAP) canister purge solenoid valve is not enabled. |
• | The amount of air flow into the engine is between 50-350 kg/h. |
• | The above conditions are met for greater than 30 seconds. |
P2188
• | The engine speed is less than 1000 RPM. |
• | The fuel system is in closed loop. |
• | The engine coolant temperature (ECT) is greater than 70°C (158°F). |
• | The intake air temperature (IAT) is less than 80°C (176°F). |
• | The evaporative emission (EVAP) canister purge solenoid valve is not enabled. |
• | The amount of air flow into the engine is less than 23 kg/h. |
• | The above conditions are met for greater than 20 seconds. |
P2192
• | The engine speed is greater than 1200 RPM. |
• | The engine load is between 10-20 percent. |
• | The fuel system is in closed loop. |
• | The engine coolant temperature (ECT) is greater than 70°C (158°F). |
• | The intake air temperature (IAT) is less than 80°C (176°F). |
• | The evaporative emission (EVAP) canister purge solenoid valve is not enabled. |
• | The above conditions are met for greater than 20 seconds. |
Conditions for Setting the DTC
P2178
The ECM detects that the Total Fuel Trim Avg. is less than a predetermined amount during cruise or accel.
P2188
The ECM detects that the Total Fuel Trim Avg. is less than a predetermined amount during idle.
P2192
The ECM detects that the Total Fuel Trim Avg. is less than a predetermined amount during a higher load.
Action Taken When the DTC Sets
DTCs P2178, P2188, and P2192 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P2178, P2188, and P2192 are Type B DTCs.
Diagnostic Aids
• | A fuel system delivery condition causes this DTC to set. Thoroughly inspect all items that cause a rich condition. Refer to
Fuel System Diagnosis
. |
• | Review the Freeze Frame/Failure Records with a scan tool. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References
for scan tool information
Circuit/System Verification
- If there are other DTCs set besides DTC P2178, P2188, or P2192, refer to
Diagnostic Trouble Code (DTC) List - Vehicle
.
- Ignition ON, observe the scan tool barometric pressure (BARO) sensor pressure parameter and compare the reading on the scan tool to the barometric pressure table. Refer to
Altitude Versus Barometric Pressure
.
- Engine at normal operating temperature, observe the scan tool Total Fuel Trim Avg. parameter . The reading should be between -22 to +23 percent.
Circuit/System Testing
- Verify none of the following conditions exist:
• | A collapsed air intake duct |
• | A restricted air filter element . |
• | Excessive fuel in the crankcase--Change the oil as necessary. |
• | The engine control module grounds for being clean, tight, and in the correct locations |
- If all conditions test normal, refer to Diagnostic Aids.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.