GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Uplander - 4WD 🢒 Engine 🢒 Engine Controls - 3.9L 🢒 DTC P1174

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P1174: Air Fuel Imbalance Bank 1

System Description

The air fuel imbalance monitor (AFIM) diagnostic detects a rich or lean cylinder to cylinder air/fuel ratio imbalance. An imbalance will result in oxygen sensor signal switching above the desired frequency. Diagnostic detection is accomplished by measuring the frequency of the pre-catalyst oxygen sensor signal. If the frequency of the oxygen sensor signal exceeds the calibrated limit, a failure is reported.

Conditions for Running the DTC
    • DTCs P0030, P0036, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0128, P0131, P0132, P0133, P0134, P0135, P0201-P0206, P0300, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P1133, P1516, P2101, P2119, P2120, P2125, P2135, P2138, P2176, P2A00, are not set.
    • The device control is not active.
    • The intrusive diagnostics is 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 greater than 10 volts, or less than 18 volts.
    • The engine run time is greater than 50 seconds.
    • The engine coolant temperature (ECT) is greater than 10°C (50°F).
    • The engine speed is greater than 1,000 RPM, but less than 4,000 RPM.
    • The mass air flow is greater than 7 g/s, but less than 400 g/s.

Conditions for Setting the DTC

The air-fuel imbalance is monitored for a predetermined amount of time before the DTC sets.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Controls Connector End Views
    •  Engine Control Module Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Troubleshooting with a Test Lamp
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Output Controls

Special Tools Required

    • J 34730-1A Fuel Pressure Gage
    •  J 39021 Fuel Injector Coil and Balance Tester
    • J-39021-450 Fuel Injector Harness Adapter

Circuit/System Testing

Important: If any DTCs other than DTC P1174 is also set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

    • Inspect the air intake system for the following:
       - Modified, damaged, or restricted components
       - Dirty or deteriorating air filter element
    • Test fuel injector balance for a rich or lean condition. Refer to Fuel Injector Diagnosis .
    • Inspect the base engine for the following:
       - The crankcase ventilation system for correct operation--Refer to Crankcase Ventilation System Inspection/Diagnosis .
       - A vacuum leak and other un-metered air downstream of the MAF sensor
       - The intake manifold for a leak
    • Inspect the exhaust system for the following:
       - An exhaust leak
       - Damaged, restricted, modified or enhanced exhaust system--Refer to Symptoms - Engine Exhaust .
    • Inspect the engine mechanical for items that could alter the air flow into the combustion chamber. Refer to Symptoms - Engine Mechanical .