2010 Cadillac Truck SRX AWD V6-2.8L Turbo Page 1852
3. 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 %.
瀚慖f not within the specified range, verify none of the following conditions exist:
* A mass air flow sensor signal that is skewed-If the Short Term Fuel Trim parameter changes greater than 20 % when the MAF sensor is
disconnected, refer to DTC P0101 (LAU) (See: P Code Charts/P0101)DTC P0101 (LF1) (See: P Code Charts/P0101).
* The air intake system after the MAF sensor for vacuum leaks
* Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool) (See: Powertrain Management/Fuel Delivery and
Air Induction/Fuel/Testing and Inspection/Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool))Alcohol/Contaminants-in-Fuel
Diagnosis (Without Special Tool) (See: Powertrain Management/Computers and Control Systems/Testing and Inspection/Component
Tests and General Diagnostics/Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool)) and Fuel System Cleaning (See:
Powertrain Management/Fuel Delivery and Air Induction/Service and Repair).
* Splits, kinks, or improper connections at the vacuum hoses.
* The fuel system is operating lean. Refer to Fuel System Diagnosis (LF1 China) (See: Powertrain Management/Fuel Delivery and Air
Induction/Fuel Pump/Testing and Inspection/Fuel System Diagnosis (China))Fuel System Diagnosis (LF1 Except China) (See:
Powertrain Management/Fuel Delivery and Air Induction/Fuel Pump/Testing and Inspection/Fuel System Diagnosis (Except China))Fuel
System Diagnosis (LAU China) (See: Powertrain Management/Fuel Delivery and Air Induction/Fuel Pump/Testing and Inspection/Fuel
System Diagnosis (China))Fuel System Diagnosis (LAU Except China) (See: Powertrain Management/Fuel Delivery and Air
Induction/Fuel Pump/Testing and Inspection/Fuel System Diagnosis (Except China)).
* Vacuum leaks at the intake manifold or throttle body
* Leaking crankcase ventilation system
* The engine control module 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 sensor, causing a lean indication.
The MAF sensor does not need to be replaced.
* Vacuum leaks that only affect one bank of the engine-For example, the intake manifold, the injector O-rings.
* Lean injectors-Refer to Fuel Injector Solenoid Coil Test (LAU) (See: Powertrain Management/Fuel Delivery and Air Induction/Fuel
Injector/Testing and Inspection/Fuel Injector Solenoid Coil Test)Fuel Injector Solenoid Coil Test (LF1, LFW) (See: Powertrain
Management/Fuel Delivery and Air Induction/Fuel Injector/Testing and Inspection/Fuel Injector Solenoid Coil Test).
* Missing, restricted, or leaking exhaust components-Refer to Symptoms - Engine Exhaust (See: Engine, Cooling and Exhaust/Exhaust
System/Testing and Inspection/Symptoms - Engine Exhaust).
* The heated oxygen sensor (HO2S) is installed securely and the electrical connector is not contacting the exhaust system.
* An engine mechanical condition-Refer to Symptoms - Engine Mechanical (See: Engine, Cooling and Exhaust/Engine/Testing and
Inspection/Symptom Related Diagnostic Procedures/Symptoms - Engine Mechanical).
4. 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.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
P2188
DTC P2178 or P2188
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
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
