For 1990-2009 cars

### 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: 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-P0205, P0220, P0222, P0223, P0300, P0411, P0412, P0418, 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, P2430, P2431, P2432, P2433, P2440, P2444, 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 60 seconds.

• | The engine coolant temperature (ECT) is greater than -20°C (-4°F).

• | The engine speed is greater than 1,000 RPM, but less than 6,000 RPM.

• | The mass air flow is greater than 20 g/s, but less than 510 g/s.

• | This DTC 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.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### 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 .
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 DTC P0106 .

4. Inspect the air induction system for modified, damaged, leaking, or restricted components.
5. Inspect the crankcase ventilation system for improper operation. Refer to Crankcase Ventilation System Inspection/Description .
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. Refer to Symptoms - Engine Exhaust .
9. Test the fuel injectors for improper operation. Refer to Fuel Injector Diagnosis .
10. Test for fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
11. Test for excessive fuel in the crankcase due to leaking injectors.
12. Test the ignition system for improper operation. Refer to Electronic Ignition (EI) System Diagnosis .
13. 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 .

### 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.

• | 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