Fuel System 1/1 Rich Control Over Limit (At Load)
P0171 - FUEL SYSTEM 1/1 RICH CONTROL OVER LIMIT (AT LOAD)
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.
Diagnostic Test
1. PRE-DIAGNOSTIC CHECK OUT
NOTE: Always perform diagnostics with a fully charged battery.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal connections can set DTCs.
NOTE: Check for applicable TSBs related to the problem.
Turn the ignition on.
With the DRB III(R), read PCM DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors. Repair as necessary.
Perform this procedure prior to symptom diagnosis.
Continue
- Go To 2
2. CHECK FOR CURRENT DTC
NOTE: Check for contaminates that may have damaged the O2 Sensor: contaminated fuel, unapproved silicone, oil and coolant.
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(R) 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(R), erase PCM DTCs.
NOTE: It maybe necessary to road test the vehicle for this DTC to set.
With the DRB III(R), read PCM DTCs.
Did this DTC set again?
Yes
- Go To 3
No
- Go To 12
3. 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(R), actuate the Fuel Pump 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 4
Above Specification
- Replace the fuel filter/pressure regulator.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
4. O2 SENSOR OPERATION
Start the engine.
Allow the engine to reach normal operating temperature.
With the DRB III(R), read the O2 Sensor voltage.
Is the voltage switching between 0.4 and 0.6 volt?
Yes
- Go To 5
No
- Go To 9
5. EVAP PURGE SOLENOID OPERATION
Turn the ignition off.
Disconnect the hoses at the Evap Purge Solenoid.
NOTE: Check connectors - Clean/repair as necessary.
Using a hand vacuum pump, apply 339 mbar (10 in. Hg) of vacuum to the Evap Purge Solenoid vacuum source port on the component side.
Did the Evap Purge Solenoid hold vacuum?
Yes
- Go To 6
No
- Replace the Evap Purge Solenoid.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
6. MAP SENSOR OPERATION
With the ignition off.
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(R) in Sensors, read the MAP Sensor vacuum value.
Is the DRB III(R) reading within 33.9 mbar (1 in. Hg) of the Vacuum Gauge reading?
Yes
- Go To 7
No
- Replace the Manifold Absolute Pressure Sensor.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
7. 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 off until the engine is cold.
Turn the ignition on.
With the DRB III(R), read the Engine Coolant Temperature 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 Engine Coolant Temperature 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 8
No
- Replace the Engine Coolant Temperature Sensor.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
8. ENGINE MECHANICAL PROBLEM
Turn the ignition off.
Check for any of the following conditions/mechanical problems.
AIR INDUCTION SYSTEM - must be free from restrictions.
ENGINE VACUUM - must be at least 440 mbar (13 in. Hg) 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.
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. Powertrain Verification Test - Ver 2
No
- Go To 12
9. O2 SENSOR
Turn the ignition off.
Disconnect the O2 Sensor harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Turn the ignition on.
With the DRB III(R), monitor the O2 Sensor voltage.
The O2 Sensor voltage should read 0.47 volt on the DRB III(R) with the connector disconnected.
Connect a jumper wire between the O2 Sensor Signal circuit and the Sensor Ground circuit in the O2 Sensor harness connector.
NOTE: The voltage should drop from 0.47 volt down to 0.0 volt with the jumper wire connected.
Did the O2 Sensor voltage drop from 0.47 volt to 0.0 volt?
Yes
- Replace the Oxygen Sensor.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
No
- Go To 10
10. O2 SIGNAL CIRCUIT
With the ignition on.
Measure the voltage of the O2 Sensor Signal circuit at the O2 Sensor harness connector.
Is the voltage above 0.47 volt?
Yes
- Check the O2 Signal circuit for damage, short to ground, open, or short to voltage. Inspect the O2 Sensor harness connector and the PCM harness connector. If OK, replace the Powertrain Control Module.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
No
- Go To 11
11. O2 SENSOR GROUND CIRCUIT
With the ignition on.
Measure the voltage of the O2 Sensor Ground circuit at the O2 Sensor harness connector.
Is the voltage below 0.1 volt?
Yes
- Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary. Replace and program the Powertrain Control Module.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
No
- Check the O2 Sensor Ground circuit for damage, short to ground, open, or short to voltage. Inspect the O2 Sensor harness connector and the PCM harness connector. If OK, replace and program the Powertrain Control Module.
- Perform POWERTRAIN VERIFICATION TEST - VER 2. Powertrain Verification Test - Ver 2
12. INTERMITTENT WIRING AND CONNECTORS
The condition that caused this DTC to set is currently not present. Inspect the related wiring harness for a possible intermittent condition.
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. 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.