(P0172) Fuel System 1/1 Lean Control Below Limit (at Load)
(P0172) FUEL SYSTEM 1/1 LEAN CONTROL BELOW LIMIT (AT LOAD)Part 1 Of 2:
Part 2 Of 2:
When Monitored and Set Condition
^ When Monitored: With the engine running in closed loop mode, the ambient/battery temperature above -7 °C (20 °F), altitude below 2590m (8500 ft). and fuel level greater than 15%.
^ Set Condition: If the PCM multiplies short term compensation by long term adaptive and a certain percentage is exceeded for two trips, the MIL illuminates and a trouble code is stored.
POSSIBLE CAUSES
RESTRICTED FUEL SUPPLY LINE
FUEL STRAINER PLUGGED
02 SENSOR SIGNAL CIRCUIT
02 SENSOR GROUND CIRCUIT
02 SENSOR HEATER OPERATION
MANIFOLD ABSOLUTE PRESSURE SENSOR OPERATION
ENGINE COOLANT TEMPERATURE SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
02 SENSOR
FUEL PUMP
FUEL CONTAMINATION/EXHAUST LEAK
Diagnostic Test
1. CHECK FOR CURRENT DTC
Note: Check for contaminates that may have damaged the 02 Sensor: contaminated fuel, unapproved silicone, oil and coolant.
Note: Diagnose any Misfire, Throttle Body, or Accelerator Pedal Position Sensor DTC(s) first, if set along with the fuel system DTC.
Note: If the PCM detects and stores a DTC, the PCM also stores the engine/vehicle operating conditions under which the DTC was set. Some of these conditions are displayed on the DRB III at the same time the DTC is displayed.
Note: Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may assist when checking for a DTC.
Turn the ignition on.
With the DRB III, erase PCM DTCs.
Note: It maybe necessary to road test the vehicle for this DTC to set.
Did this DTC set again?
Yes>> Go To 2
No>> Go To 12
2. CHECKING FUEL PRESSURE
WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT PRESSURE (EVEN WITH THE ENGINE OFF). BEFORE TESTING OR SERVICING ANY FUEL SYSTEM HOSE, FITTING OR LINE, THE FUEL SYSTEM PRESSURE MUST BE RELEASED.
Turn the ignition off.
Install a fuel pressure gauge.
Turn the ignition on.
With the DRB III, actuate the Fuel Pump Relay and observe the fuel
pressure gauge.
Note: Fuel pressure specification is 3.7 to 4.2 bar (54 to 61 psi).
Turn the ignition off.
CAUTION: Stop All Actuations.
Choose a conclusion that best matches your fuel pressure reading.
Within Specification
Go To 3
Below Specification
Go To 11
3. 02 SENSOR OPERATION
Start the engine.
Allow the engine to reach normal operating temperature.
With the DRB III, read the 02 Sensor voltage.
Is the voltage switching between 0.4 and 0.6 volt?
Yes>> Go To 4
No>> Go To 8
4. 02 SENSOR HEATER OPERATION
Turn the ignition off.
Note: Allow the 02 Sensor to cool down before continuing the test.
Raising the hood may help in reducing under hood temperatures.
Turn the ignition on.
With the DRB III, actuate the 02 Heater Test.
With the DRB III, monitor 02 Sensor voltage for at least 2 minutes.
Does the voltage stay above 0.47 volt?
Yes>> Replace the Oxygen Sensor in accordance with the Service Information.
Perform Powertrain Verification Test - Ver 2
No>> Go To 5
5. MAP SENSOR OPERATION
Connect a Vacuum Gauge to a Manifold Vacuum source.
Start the engine.
Allow the engine to idle.
Note: If engine will not idle, maintain a constant RPM above idle.
With the DRB III in Sensors, read the MAP Sensor vacuum value.
Is the DRB III reading within 33.9 mbar (1 in. Hg) of the Vacuum Gauge reading?
Yes>> Go To 6
No>> Replace the Manifold Absolute Pressure Sensor in accordance with the Service Information.
Perform Powertrain Verification Test - Ver 2
6. ECT SENSOR OPERATION
Note: For this test to be valid, the thermostat must be operating correctly.
Note: This test works best if performed on a cold engine (cold soak) Turn the ignition on.
With the DRB III, read the Engine Coolant Temperature (ECT) Sensor value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature.
Note: If engine coolant temperature is above 82 °C (180 °F), allow the engine to cool until 65 °C (150 °F) is reached.
Start the Engine.
During engine warm-up, monitor the ECT Sensor value. The temperature value change should be a smooth transition from start up to normal operating temperature 82 °C (180 °F). The value should reach at least 82 °C (180 °F).
Did the Engine Coolant Temperature value increase with a smooth transition and did it reach at least 82 °C (180 °F)?
Yes>> Go To 7
No>> Replace the Engine Coolant Temperature Sensor in accordance with the Service Information.
Perform Powertrain Verification Test - Ver 2
7. ENGINE MECHANICAL PROBLEM
Check for any of the following conditions/mechanical problems. AIR
INDUCTION SYSTEM - must be free from leaks.
ENGINE VACUUM - must be at least 13 inches in neutral
ENGINE VALVE TIMING - must be within specifications
ENGINE COMPRESSION - must be within specifications
ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.
ENGINE CRANKCASE VENT SYSTEM - must flow freely
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - must not have any internal vacuum leaks.
FUEL - must be free of contamination
FUEL INJECTOR - must not be plugged or restricted; harness connectors must be connected to the correct injectors.
Are there any engine mechanical problems?
Yes>> Repair as necessary.
Perform Powertrain Verification Test - Ver 2
No>> Go To 12
8. 02 SENSOR
Turn the ignition off.
Disconnect the 02 Sensor harness connector.
Note: Check connectors-Clean/repair as necessary.
Turn the ignition on.
With the DRB III, monitor the 02 Sensor voltage.
The 02 Sensor voltage should read 0.47 volts on the DRB III with the harness connector disconnected.
Using a jumper wire, jump from the 02 Sensor Signal circuit to the 02 Sensor Ground circuit in the 02 Sensor harness connector.
Note: The voltage should drop from 0.47 volts down to 0.0 volts with the jumper wire connected.
Did the 02 Sensor voltage drop from 0.47 volts to 0.0 volt?
Yes>> Replace the Oxygen Sensor in accordance with the Service Information.
Perform Powertrain Verification Test - Ver 2
No>> Go To 9
9. 02 SENSOR SIGNAL CIRCUIT
With the ignition on.
With the DRB III, monitor the 02 Sensor voltage.
Is the voltage below 0.45 volts?
Yes>> Go to10
No>> Check the 02 Sensor Signal circuit for a short to ground, open, or short to voltage. Inspect the 02 Sensor harness connector and the PCM harness connector. If OK, replace and program the Powertrain Control Module in accordance with the Service Information.
Perform Powertrain Verification Test - Ver 2
10. 02 SENSOR GROUND CIRCUIT
With the ignition on.
Measure the voltage on the 02 Sensor Ground circuit in the 02 Sensor harness connector.
Is the voltage below 0.1 volt?
Yes>> Check the fuel system for contaminates. Also, check the exhaust system for any leaks.
Perform Powertrain Verification Test - Ver 2
No>> Check the 02 Sensor Ground circuit for a short to ground, open, or short to voltage. Inspect the 02 Sensor harness connector and the PCM harness connector. If OK, replace and program the Powertrain Control Module in accordance with the Service Information.
Perform Powertrain Verification Test - Ver 2
11. FUEL STRAINER
WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT PRESSURE (EVEN WITH THE ENGINE OFF). BEFORE TESTING OR SERVICING ANY FUEL SYSTEM HOSE, FITTING OR LINE, THE FUEL SYSTEM PRESSURE MUST BE RELEASED
With the ignition off. Remove and inspect the Fuel Strainer.
Is the Fuel Strainer plugged?
Yes>> Replace the Fuel Strainer in accordance with the Service Information.
Perform Powertrain Verification Test - Ver 2
No>> Replace the Fuel Pump in accordance with the Service Information.
Perform Powertrain Verification Test - Ver 2
12. INTERMITTENT WIRING AND CONNECTORS
The conditions necessary to set this DTC are not present at this time.
Note: Check connectors-Clean/repair as necessary. Poor pin to terminal connections can set DTCs. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors specific to this DTC. Wiggle the wires while checking for shorts and open circuits.
Note: Check for any Technical Service Bulletins that may apply.
Were there any problems found?
Yes>> Repair as necessary.
Perform Powertrain Verification Test - Ver 2
No>> The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.