P1174

DTC P1174

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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
- Fuel Trim Cylinder Balance

Circuit/System Description

The Fuel Trim Cylinder Balance diagnostic detects a rich or a lean cylinder-to-cylinder air/fuel ratio imbalance. 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, P0053, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0131, P0132, P0133, P0134, P0135, P0201-P0204, P0220, P0222, P0223, P0300, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P0506, P0507, P060D, P1133, P1516, P2101, P2119, P2120, P2122, P2123, P2125, P2127, P2128, P2135, P2138, P2176, P2A00 are not set.
* The device control is not active.
* The intrusive diagnostics are not active.
* The engine overspeed protection 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.
* DTC P1174 runs continuously when the above conditions are met.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

DTC P1174 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P1174 is a Type B DTC.

Diagnostic Aids

* The Fuel Trim Cylinder Balance diagnostic is very sensitive to 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.

Circuit/System Testing

1. Read and record the Freeze Frame/Failure Records data taking note of the speed and load at which the DTC set.
2. Diagnose any other DTCs that are set. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. Diagnostic Trouble Code Descriptions
3. 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 to Altitude Versus Barometric Pressure.

4. Inspect the air induction system for modified, damaged, leaking, or restricted components.
5. Inspect the crankcase ventilation system for improper operation.
6. Inspect the vacuum hoses for splits, kinks, and improper connections.
7. Inspect for vacuum leaks at the intake manifold, the throttle body, and the injector O-rings.
8. Test for a restricted, damaged, leaking, or modified exhaust system from the catalytic converter forward.
9. Test the fuel injectors for improper operation.
10. Test for fuel contamination.
11. Test for excessive fuel in the crankcase due to leaking injectors.
12. Test the ignition system for improper operation.
13. Test the engine for any mechanical conditions such as sticking valves, lifters, etc., which could alter the flow into the combustion chamber.

Repair Instructions

Perform the Diagnostic Repair Verification 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. Verification Tests

* Air Cleaner Assembly Replacement
* Air Cleaner Element Replacement
* Fuel Injector Replacement
* Fuel System Cleaning
* Fuel Tank Draining
* Ignition Coil Replacement
* Intake Manifold Replacement
* Spark Plug Replacement
* Throttle Body Assembly Replacement