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Dodge Ram Truck 1500-2500-3500. Manual - part 1179

P0171-FUEL SYSTEM 1/1 LEAN

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ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

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P0171-FUEL SYSTEM 1/1 LEAN (CONTINUED)

For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS).

For a complete wiring diagram Refer to Section 8W.

Theory of Operation

The fuel feedback system will maintain a stoiciometric fuel/air mixture, 14.7:1, by modifying the injector pulsewidth
according to the oxygen content of the exhaust gas. The PCM makes short term and long term fuel corrections to
maintain stoiciometric 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 20 deg. F and altitude
below 8500 ft.

•

Set Condition:
If the PCM multiplies short term compensation by long term adaptive and a certain percentage is exceeded for
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

Possible Causes

FUEL PRESSURE OUT OF SPECS

RESTRICTED FUEL SUPPLY LINE

FUEL PUMP INLET STRAINER PLUGGED

FUEL PUMP MODULE

O2 SENSOR

(K41) O2 SENSOR 1/1 SIGNAL CIRCUIT SHORTED TO GROUND

O2 SENSOR 1/1 HEATER OPERATION

TP SENSOR

MAP SENSOR

ECT SENSOR

ENGINE MECHANICAL CONDITION

FUEL FILTER/PRESSURE REGULATOR

PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).

Diagnostic Test

GOOD TRIP EQUAL TO ZERO

NOTE: Check for contaminates that may have damaged the O2 Sensor: contaminated fuel, unapproved sil-
icone, oil and coolant.
Ignition on, engine not running.

With the scan tool, read DTCs and record the related Freeze Frame data.

Is the Good Trip Counter displayed and equal to zero?

Yes

>> Go To 2

>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

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ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

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P0171-FUEL SYSTEM 1/1 LEAN (CONTINUED)

CHECKING FUEL PRESSURE

WARNING: The fuel system is under a constant pressure (even with the engine off). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure must be released.
Install a fuel pressure gauge.

Ignition on, engine not running.

With the scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.

NOTE: Fuel pressure specification is 379 KPa +/- 14 KPa (55 psi +/- 2 psi).
Turn the ignition off.

Choose a conclusion that best matches your fuel pressure reading.

Below Specification

Go To 3

Within Specification

Go To 6

Above Specification

Replace the fuel filter/pressure regulator.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

CAUTION: Stop All Actuations.

RESTRICTED FUEL SUPPLY LINE

Turn the ignition off.

Install special 5/16 fuel line adapter tool #6539 or #6631 for 3/8 fuel line adapter, between the disconnected fuel line
and the fuel pump module.

Attach a fuel pressure test gauge to the T fitting on tool #6539 or #6631.

Ignition on, engine not running.

With the scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.

NOTE: Fuel pressure specification is 379 KPa +/- 14 KPa (55 psi +/- 2 psi).

CAUTION: Stop All Actuations.

Is the fuel pressure within specification?

Yes

>> Repair or replace fuel supply line as necessary.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

>> Go To 4

FUEL PUMP INLET STRAINER

Turn the ignition off.

Is the Fuel Inlet Strainer plugged?

Yes

>> Replace the Fuel Pump Inlet Strainer.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

>> Go To 5

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ENGINE - ELECTRICAL DIAGNOSTICS - SRT-10

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P0171-FUEL SYSTEM 1/1 LEAN (CONTINUED)

FUEL PUMP MODULE

If there are no possible causes remaining, view repair.

Repair

Replace the Fuel Pump Module.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

O2 SENSOR OPERATION

Turn the ignition off.

NOTE: Wait a minimum of 10 minutes to allow the O2 Sensor and Exhaust System to cool down before
continuing the test.
Ignition on, engine not running.

With the scan tool, monitor all of the O2 Sensor voltage readings.

Is the voltage above 4.5 volts?

Yes

>> Go To 7

>> Go To 13

O2 SENSOR HEATER OPERATION

Turn the ignition off.

NOTE: Wait a minimum of 10 minutes to allow the O2 Sensor to cool down before continuing the test.
Ignition on, engine not running.

With the scan tool, actuate the 1/1 O2 Heater Test.

With the scan tool, monitor all O2 Sensor voltage readings for at least 2 minutes.

Does the voltage stay above 4.5 volts for any of the O2 Sensors?

Yes

>> Replace the O2 Sensor that had the voltage reading above 4.5 volts.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

>> Go To 8

TP SENSOR VOLTAGE GREATER THAN 0.92 OF A VOLT WITH THROTTLE CLOSED

With the scan tool, read TP Sensor voltage.

NOTE: The throttle must be against the stop.

Is the voltage 0.92 of a volt or less with the Throttle closed?

Yes

>> Go To 9

>> Check for a binding throttle condition. If OK, replace the Throttle Position Sensor.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

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