PRE-RELEASE
DTC P2178 or P2188
| DTC P2178 or P2188 |
| Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
provides an overview of each diagnostic category.
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| DTC Descriptors |
DTC P2178
Fuel Trim System Rich at Cruise or Acceleration
DTC P2188
Fuel Trim System 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 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
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Before the ECM can report DTC P2178 failed, DTCs P0008, P0009, P0010, P0011, P0013, P0014, P0016, P0017, P0018, P0019, P0020, P0021, P0023, P0024, P0101, P0121, P0122, P0123, P0133, P0201, P0202, P0203, P0204, P0205, P0206, P0221, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0335, P0336, P0338, P0443, P0458, P0459, P0461, P0462, P0463, P2068 P2088, P2089, P2090, P2091, P2092, P2093, P2094, and P2095 must run and pass.
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The engine speed is between 1,200-3,400 RPM.
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The mass air flow is between 7-83 grams/second.
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The throttle angle is less than 100 percent.
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The engine load is between 17-55 percent.
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The fuel system is in closed loop.
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The engine is not in decel fuel cut-off (DEFCO).
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The long term fuel trim is active.
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The engine coolant temperature (ECT) is greater than 60°C (140°F).
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The intake air temperature (IAT) is less than 61°C (142°F).
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The evaporative emission (EVAP) canister purge solenoid valve is not enabled.
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The fuel level is greater than 12 percent.
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The amount of air flow into the engine is greater than 7,000 grams.
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DTC P2178 run continuously once the above conditions are met for at least 300 seconds.
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P2188
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Before the ECM can report DTC P2188 failed, DTCs P0008, P0009, P0010, P0011, P0013, P0014, P0016, P0017, P0018, P0019, P0020, P0021, P0023, P0024, P0101, P0121, P0122, P0123, P0133, P0201, P0202, P0203, P0204, P0205, P0206, P0221, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0335, P0336, P0338, P0443, P0458, P0459, P0461, P0462, P0463, P2068 P2088, P2089, P2090, P2091, P2092, P2093, P2094, and P2095 must run and pass.
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The engine speed is between 480-1,001 RPM.
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The engine load is between 7-32 percent.
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The MAF is between 1-8 grams per second.
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The fuel system is in closed loop.
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The engine is not in decel fuel cut-off (DEFCO).
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The long term fuel trim is active.
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The engine coolant temperature (ECT) is greater than 60°C (140°F).
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The intake air temperature (IAT) is less than 61°C (142°F).
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The evaporative emission (EVAP) canister purge solenoid valve is not enabled.
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The fuel level is greater than 12 percent.
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The amount of air flow into the engine is greater than 7,000 grams.
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DTC P2188 run continuously once the above conditions are met.
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| Conditions for Setting the DTC |
P2178
The Total Fuel Trim Avg. is less than -22 percent. The condition exists for 4 seconds or for a cumulative of 30 seconds.P2188
The Total Fuel Trim Avg. is less than -40 percent. The LT FT Idle/Decel is less than -6 percent. The condition exists for 4 seconds or for a cumulative of 30 seconds.| Action Taken When the DTC Sets |
DTCs P2178 and P2188 are Type B DTCs.
| Conditions for Clearing the MIL/DTC |
DTCs P2178 and P2188 are Type B DTCs.
| Diagnostic Aids |
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A fuel system delivery condition causes this DTC to set. Thoroughly inspect all items that cause a rich condition. Refer to
Fuel System Diagnosis (LF1 China)
Fuel System Diagnosis (LF1 Except China)
Fuel System Diagnosis (LAU China)
Fuel System Diagnosis (LAU Except China)
.
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Review the Freeze Frame/Failure Records with a scan tool.
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| Reference Information |
Schematic Reference
Engine Controls Schematics (3.0L (LF1)) Engine Controls Schematics (2.8L (LAU))
Connector End View Reference
Component Connector End Views
Electrical Information Reference
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
| Circuit/System Verification |
| 1. |
Check the DTC information with a diagnostic tool. DTC P2178 or P2188 should not be activated.
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| 2. |
If there are other DTCs set besides DTC P2178 or P2188, refer to
Diagnostic Trouble Code (DTC) List - Vehicle
to diagnosis the applicable DTC.
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| 3. |
Ignition ON, observe the BARO pressure parameter and compare the reading on the scan tool to the barometric pressure table. Refer to
Altitude Versus Barometric Pressure
.
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If the BARO pressure is not within the range specified for your altitude, refer to
DTC P2227, P2228, or P2229 (LAU)
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Engine at normal operating temperature, observe the Average Total Fuel Trim parameter with a scan tool. The Average Total Fuel Trim should be between -22 to +23 percent.
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If not within the specified range, inspect for the following conditions:
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A mass air flow sensor signal that is skewed. If the Short Term Fuel Trim parameter changes greater than 20 percent when the MAF sensor is disconnected, refer to
DTC P0101 (LAU)
DTC P0101 (LF1)
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A collapsed air intake duct
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A restricted air filter element-Refer to
Air Cleaner Element Replacement (LAU)
Air Cleaner Element Replacement (LF1)
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The MAF sensor for foreign objects.
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Excessive fuel in the crankcase-Change the oil as necessary.
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Fuel contamination-Refer to
Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool)
Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool)
and
Fuel System Cleaning
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The engine control module grounds for being clean, tight, and in the correct locations
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Rich injectors-Refer to
Fuel Injector Solenoid Coil Test (LAU)
Fuel Injector Solenoid Coil Test (LF1, LFW)
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Restricted exhaust system-Refer to
Symptoms - Engine Exhaust
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An engine mechanical condition-Refer to
Symptoms - Engine Mechanical
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| 7. |
Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
