2010 Cadillac CTS Sedan AWD V6-3.6L Page 1122
* A cracked EVAP canister
* Evaporative pipes obstructed or leaking
* The crankcase ventilation system for leaks
* A mass air flow (MAF) sensor signal that is skewed-If the Short Term FT parameters for both banks changes greater than 20 % when the
MAF sensor is disconnected, refer to DTC P0101 (w/LLT) (See: P Code Charts/P0101)DTC P0101 (LF1) (See: P Code Charts/P0101).
* Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) (See: Powertrain Management/Computers
and Control Systems/Testing and Inspection/Component Tests and General Diagnostics/Alcohol/Contaminants-in-Fuel Diagnosis (with
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)).
* Missing, restricted, or leaking exhaust components-Refer to Symptoms - Engine Exhaust (See: Engine, Cooling and Exhaust/Exhaust
System/Testing and Inspection/Symptoms - Engine Exhaust).
* Malfunctioning fuel injectors-Refer to Fuel Injector Solenoid Coil Test (w/LLT) (See: Powertrain Management/Computers and Control
Systems/Testing and Inspection/Component Tests and General Diagnostics/Fuel Injector Solenoid Coil Test)Fuel Injector Solenoid Coil
Test (w/LF1) (See: Powertrain Management/Fuel Delivery and Air Induction/Fuel Injector/Testing and Inspection) ,
* The air intake duct for being collapsed or restricted
* The air filter for being dirty or restricted
* Objects blocking the throttle body
* The evaporative emissions control system for improper operation
* Excessive fuel in the crankcase-Change the oil as necessary.
5. If all conditions test normal, test the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical (See: Engine, Cooling and
Exhaust/Engine/Testing and Inspection/Symptom Related Diagnostic Procedures/Symptoms - Engine Mechanical).
6. 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.
P0172
DTC P0171, P0172, P0174, or P0175 (LF1)
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 P0171
- Fuel Trim System Lean Bank 1
DTC P0172
- Fuel Trim System Rich Bank 1
DTC P0174
- Fuel Trim System Lean Bank 2
DTC P0175
- Fuel Trim System Rich Bank 2
Circuit/System Description
The engine control module (ECM) controls a Closed Loop air/fuel metering system in order to provide the best possible combination of
driveability, fuel economy, and emission control. The ECM monitors the heated oxygen sensor (HO2S) signal voltage, and adjusts the fuel delivery
based on the signal voltage while in Closed Loop. A change made to the fuel delivery changes the long and short term fuel trim values. The short
term fuel trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The long term fuel trim
values change in response to trends in the short term fuel trim The long term fuel trim makes coarse adjustments to fueling in order to re-center and
restore control to short term fuel trim. The ideal fuel trim values are around 0 %. A positive fuel trim value indicates that the ECM is adding fuel in
order to compensate for a lean condition. A negative fuel trim value indicates that the ECM is reducing the amount of fuel in order to compensate
for a rich condition.
If the ECM detects an excessively lean condition, DTC P0171 or P0174 sets. If the ECM detects an excessively rich condition, DTC P0172 or
