P0174
P0174-FUEL SYSTEM 2/1 LEAN
For a complete wiring diagram Consult Diagrams/Electrical.
Theory of Operation
The fuel feedback system will maintain a stoichiometric fuel/air mixture, 14.7:1, by modifying the injector pulse width according to the oxygen content of the exhaust gas. The PCM makes short term and long term fuel corrections to maintain stoichiometric fuel/air ratio for best catalytic converter efficiency. Short term fuel correction is based on upstream O2 sensor output and is designed for quick engine response. The long term fuel correction compensated for variations in the engine specifications, sensor tolerances and component aging and is designed to correct rich and lean conditions over a longer period of time.
- When Monitored:
With the engine running in closed loop mode, the ambient/battery temperature above -6.7° C (20° F) and altitude below 2590.8 m (8500 ft).
- Set Condition:
If the PCM multiplies short term compensation by long term adaptive and a purge fuel multiplier and the result is below a certain value for 30 seconds over two trips, a freeze frame is stored, the MIL illuminates and a trouble code is stored. Two Trip Fault. Three good trips to turn off the MIL.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Initial Inspection and Diagnostic Overview
Diagnostic Test
1. DTC IS ACTIVE
Diagnose and repair any other active component or circuit DTCs before continuing with this procedure.
Turn the ignition on.
With the scan tool, select View DTCs. Copy DTC and Freeze Frame information.
Start the engine and allow it to reach operating temperature.
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.
NOTE: Attempt to operate the vehicle under conditions similar to which the DTC was set.
NOTE: It may be necessary to test drive the vehicle within the DTC monitoring conditions in order for this DTC to set.
With a scan tool, select View DTCs.
Is the DTC Active or Pending at this time?
Yes
- Go to 2
No
- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking For An Intermittent DTC
2. CHECKING THE FUEL DELIVERY SYSTEM
Perform the diagnostic procedure for *CHECKING THE FUEL DELIVERY SYSTEM. Checking the Fuel Delivery System
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test
No
- Go to 3
3. CHECKING THE EXHAUST SYSTEM FOR LEAKS
Turn the ignition off.
Raise the vehicle.
WARNING: The normal operating temperature of the exhaust system is very high. Never work around or attempt to service any part of the exhaust system until it has cooled. Special care should be taken when working near the catalytic converter. The temperature of the converter rises to a high level after a short period of engine operating time
Connect Exhaust Cone #8404-EC or #8404-EC to Air Pressure Regulator (with hose) #W-18-MIL-1146AS.
CAUTION: The air pressure must not exceed 27.6 kPa (4 psi), otherwise engine damage can occur.
Attach shop air to the air pressure regulator.
Adjust the Air Pressure Regulator to 27.6 kPa (4 psi)
Insert the exhaust cone into the vehicle tail pipe.
If the vehicle is equipped with dual exhaust. Use the #8404-ECT with equipped attached plug, plug one side of the dual exhaust pipe. Pressurize the other as described above.
Apply Mopar(R) Air Leak Detector PN# 05191804AA (or an equivalent leak finder liquid) to the following areas:
- All welded joints from the exhaust manifold to 152.4 mm (6 inches) behind the downstream O2 sensor
- O2 sensor seal points
- O2 sensor boss welds
- Flange/joint connection(s)
- Exhaust manifold to cylinder head connection(s)
- EGR solenoid gasket base and tube seal points (if equipped)
Watch for the liquid/soapy water to bubble.
Use the following definitions to help determine if system or component repair/replacement is necessary:
Type 1 Leak is defined as a leak where very small foam like bubbles 1 mm (0.04 of an inch) or less appear.
Any Type 1 or greater leaks found in welded joints, O2 sensor seal points or O2 sensor boss welds must be repaired or the component must be replaced.
Type 2 Leak is defined as a leak where larger bubbles pea size, 8 mm (0.3 of an inch) or greater appear.
Any Type 2 or greater leaks found in flange or joint connections, exhaust manifold to cylinder head connections, or EGR gasket and tube seal points must be repaired or the components must be replaced.
If a leak is found that matches the above definition, repair or replace the component as necessary.
Once the repair is complete, repeat the procedure to verify that all leaks have been repaired.
Were any exhaust leaks found?
Yes
- Repair or replace the leaking exhaust parts as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test
No
- Go to 4
4. CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR OPERATION
Perform the diagnostic procedure for *CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR OPERATION. Checking the Engine Coolant Temperature Sensor Operation
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test
No
- Go to 5
5. CHECKING THE MAP SENSOR OPERATION
Perform the diagnostic procedure for *CHECKING THE MAP SENSOR OPERATION. Checking the MAP Sensor Operation
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test
No
- Go to 6
6. CHECKING THE OXYGEN SENSOR OPERATION
Perform the diagnostic procedure for *CHECKING THE OXYGEN SENSOR OPERATION. Checking the Oxygen Sensor Operation
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test
No
- Go to 7
7. CHECKING THE ENGINE MECHANICAL SYSTEM
Perform the diagnostic procedure for *CHECKING THE ENGINE MECHANICAL SYSTEM. Checking the Engine Mechanical System
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test
No
- Go to 8
8. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors relative to the components tested in this procedure.
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Monitor the scan tool data relative to the components tested in this procedure and wiggle test the wiring and connectors.
Look for the data to change or for a DTC to set during the wiggle test.
Search for any Technical Service Bulletins that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test
No
- Replace and program the PCM.
- Perform the PCM Verification Test. Powertrain Verification Test