Mechanics

CHEVROLET SILVERADO ENGINE PROBLEM

2009 Chevrolet Silverado • 12,000 miles

Check engine light came on, and it runs rough. Bogs down on acceleration. Code scanner shows PO171, P1174 and P1175. Could dirty fuel be the cause of these code readings?
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March 26, 2013.



1175

DTC P1174 or P1175

Diagnostic Instructions

Perform theDiagnostic System Check - Vehicle (See: Testing and Inspection\Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
ReviewStrategy Based Diagnosis (See: Testing and Inspection\Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
Diagnostic Procedure Instructions (See: Testing and Inspection\Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptors
DTC P1174
Fuel Trim Cylinder Balance Bank 1
DTC P1175
Fuel Trim Cylinder Balance Bank 2
Circuit/System Description

The Fuel Trim Cylinder Balance diagnostic detects a rich or lean cylinder to cylinder air/fuel ratio imbalance in each bank. The diagnostic monitors the pre-catalyst heated oxygen sensor (HO2S) signal's frequency and amplitude characteristics by calculating an accumulated voltage over a predetermined sample period. An imbalance is indicated when multiple samples of the accumulated voltage are consistently higher than the desired value.

Conditions for Running the DTC

DTCs P0030, P0036, P0050, P0053, P0059, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0128, P0131, P0132, P0133, P0134, P0135, P0151, P0152, P0153, P0154, P0155, P0201-P0206, P0300, P0301-P0306, P0411, P0412, P0418, P0442, P0443, P0446, P0449, P0452, P0453, P0454, P0455, P0496, P1133, P1153, P1516, P2101, P2119, P2120, P2125, P2135, P2138, P2176, P2431, P2432, P2433, P2440, P2A00, P2A03 are not set.
The device control is not active.
The intrusive diagnostics are not active.
The engine overspeed protection is not active.
The power take-off (PTO) is not active.
The traction control is not active.
The fuel control is in air-fuel Closed Loop.
The system voltage is more than 10 volts, or less than 18 volts.
The engine run time is greater than 100 seconds.
The engine coolant temperature (ECT) is greater than -20°C (-4°F).
The engine speed is greater than 425 RPM, but less than 6,000 RPM.
The mass air flow is greater than 25 g/s, but less than 510 g/s.
Conditions for Setting the DTC

Multiple samples of the pre-catalyst HO2S accumulated voltage are consistently greater than the desired value.

Action Taken When the DTC Sets

DTCs P1174 and P1175 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P1174 and P1175 are Type B DTCs.

Diagnostic Aids

The fuel trim cylinder balance diagnostic is very sensitive to heated oxygen sensor (HO2S) design. A non-OE sensor or an incorrect part number may set a false DTC.
Monitoring the misfire current counters, or misfire graph, may help to isolate the cylinder that is causing the condition.
Reference Information
Schematic Reference

Engine Controls Schematics (See: Powertrain Management\Diagrams\Electrical)
Connector End View Reference

Component Connector End Views (See: Diagrams\Connector Views)
Electrical Information Reference

Circuit Testing (See: Testing and Inspection\Component Tests and General Diagnostics)
Troubleshooting with a Test Lamp (See: Testing and Inspection\Component Tests and General Diagnostics)
Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection\Component Tests and General Diagnostics)
Wiring Repairs (See: Testing and Inspection\Component Tests and General Diagnostics)
DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (See: Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (See: Testing and Inspection\Programming and Relearning) for scan tool information

Circuit/System Testing

Read and record the Freeze Frame/Failure Records data taking note of the speed and load at which the DTC set.
Diagnose any other DTCs that are set. Refer to Diagnostic Trouble Code (DTC) List - Vehicle (See: Diagnostic Trouble Code Descriptions).
With the engine idling and the transmission in the Park or Neutral position, observe the manifold absolute pressure (MAP) sensor parameter. The MAP sensor parameter should be between 19-42 kPa.
¤ If the MAP sensor parameter is not between 19-42 kPa, refer toDTC P0106 (See: P0106) orDTC P0107 or P0108 (See: P0107).
Inspect the air induction system for modified, damaged, leaking, or restricted components.
Inspect the crankcase ventilation system for improper operation.
Inspect the vacuum hoses for splits, kinks, and improper connections.
Inspect for vacuum leaks at the intake manifold, the throttle body, and the injector O-rings.
Test for a restricted, damaged, leaking, or modified exhaust system from the catalytic converter forward. Refer to Symptoms - Engine Exhaust (See: Engine, Cooling and Exhaust\Exhaust System\Testing and Inspection\Symptom Related Diagnostic Procedures\Symptoms - Engine Exhaust).
Test the fuel injectors for improper operation. Refer to Fuel Injector Diagnosis (w/CH47976) (See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Component Tests and General Diagnostics\Fuel Injector Diagnosis (With CH 47976))Fuel Injector Diagnosis (w/J39021 or w/Tech 2) (See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Component Tests and General Diagnostics\Fuel Injector Diagnosis (w/J39021 or w/Tech 2)).
Test for fuel contamination. Refer to 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))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)).
Test for excessive fuel in the crankcase due to leaking injectors.
Test the ignition system for improper operation. Refer to Electronic Ignition System Diagnosis (See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Component Tests and General Diagnostics\Electronic Ignition System Diagnosis).
Test the engine for any mechanical conditions such as sticking valves, lifters, etc, which could alter the flow into the combustion chamber. Refer to Symptoms - Engine Mechanical (See: Engine, Cooling and Exhaust\Engine\Testing and Inspection\Symptom Related Diagnostic Procedures\- Symptoms - Engine Mechanical).
Repair Instructions

Perform theDiagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure. Verify the repair under the same speed and load as noted in the Freeze Frame/Failure Records data recorded during testing.

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171,174 are lean codes.

Roy

ASEMaster6371
Apr 25, 2013.