Jeep XJ. Manual — part 831
TEST
ACTION
APPLICABILITY
4
Turn the ignition off.
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.
Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.
Is the Fuel Inlet Strainer plugged?
All
Yes
→
Replace the Fuel Pump Inlet Strainer.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
No
→
5
If there are no possible causes remaining, view repair.
All
Repair
Replace the Fuel Pump Module.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
6
Turn the ignition on
With the DRBIII
t, read the O2 Sensor voltage.
Is the voltage between 0.4 to 0.6 volt?
All
Yes
→
No
→
7
Turn the ignition off.
NOTE: Wait a minimum of 10 minutes to allow the O2 Sensor to cool down
before continuing the test. Allow the O2 Sensor voltage to stabilize between
0.4 to 0.6 volts.
Turn the ignition on.
With the DRBIII
t, actuate the O2 Heater Test.
With the DRBIII
t, monitor O2 Sensor voltage for at least 2 minutes.
Does the voltage stay between 0.4 and 0.6 volt?
All
Yes
→
Replace the O2 Sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
No
→
8
Turn the ignition on.
With the DRBIII
t, read TP Sensor voltage.
NOTE: The throttle must be against the stop.
Is the voltage 0.92 or less with the Throttle closed?
All
Yes
→
No
→
Check for a binding throttle condition. If OK, replace the Throttle
Position Sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
9
Turn the ignition on.
With the DRBIII
t, read the TP Sensor voltage.
While monitoring the DRBIII
t, slowly open and close the throttle.
Does the voltage increase and decease smoothly?
All
Yes
→
No
→
Replace the Throttle Position Sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
85
DRIVEABILITY - GAS
P0171-1/1 FUEL SYSTEM LEAN —
Continued
TEST
ACTION
APPLICABILITY
10
Turn 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 DRBIII
t in Sensors, read the MAP Sensor vacuum value.
Is the DRBIII
t reading within 19 of the Vacuum Gauge reading?
All
Yes
→
No
→
Replace the MAP Sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
11
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 DRBIII
t, 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 temp
value change should be a smooth transition from start up to normal operating temp
82°C (180°F). The value should reach at least 82°C (180°F).
Did the Engine Coolant Temperature increase smoothly and did it reach at least 82°C
(180°F)?
All
Yes
→
No
→
Replace the Engine Coolant Temperature Sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
12
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 PCV SYSTEM - must flow freely
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - no internal vacuum leaks
FUEL - must be free of contamination
FUEL INJECTOR - plugged or restricted injector; control wire not connected to
correct injector
Are there any engine mechanical problems?
All
Yes
→
Repair as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
No
→
Test Complete.
13
Turn the ignition on.
Disconnect the O2 Sensor harness connector.
With the DRBIII
t, monitor the O2 Sensor voltage.
Is the O2 Sensor voltage between 0.40 to 0.60 volt?
All
Yes
→
Replace the O2 Sensor
Perform POWERTRAIN VERIFICATION TEST VER - 5.
No
→
86
DRIVEABILITY - GAS
P0171-1/1 FUEL SYSTEM LEAN —
Continued
TEST
ACTION
APPLICABILITY
14
Turn the ignition off.
Disconnect the O2 Sensor harness connector.
Disconnect the PCM harness connector.
Measure the resistance of the O2 Sensor Signal circuit in the PCM harness connector
to ground.
Is the voltage above 5.0 ohms?
All
Yes
→
Repair the O2 Sensor Signal for a short to ground.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
No
→
15
If there are no possible causes remaining, view repair.
All
Repair
Replace and program the Powertrain Control Module Module in
accordance with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
16
NOTE: Check for contaminates that may have damaged the O2 Sensor:
contaminated fuel, unapproved silicone, oil and coolant.
WARNING: KEEP CLEAR OF THE ENGINE’S MOVING PARTS.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRBIII
t
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DRBIII
t Freeze Frame information. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?
All
Yes
→
Repair as necessary
Perform POWERTRAIN VERIFICATION TEST VER - 5.
No
→
Test Complete.
87
DRIVEABILITY - GAS
P0171-1/1 FUEL SYSTEM LEAN —
Continued
Symptom List:
P0172-1/1 FUEL SYSTEM RICH
P0175-2/1 FUEL SYSTEM RICH
Test Note:
All symptoms listed above are diagnosed using the same tests.
The title for the tests will be P0172-1/1 FUEL SYSTEM RICH.
When Monitored and Set Condition:
P0172-1/1 FUEL SYSTEM RICH
When Monitored:
With the engine running in closed loop mode, the ambient/battery
temperature above 20 deg. F and altitude below 8000 ft.
Set Condition:
If the PCM multiplies short term compensation by long term adaptive and
the result is below a certain value for two trips, a freeze frame is stored, the MIL
illuminates and a trouble code is stored.
P0175-2/1 FUEL SYSTEM RICH
When Monitored:
With the engine running in closed loop mode, the ambient/battery
temperature above 20 deg. F and altitude below 8000 ft.
Set Condition:
If the PCM multiplies short term compensation by long term adaptive and
the result is below a certain value for two trips, a freeze frame is stored, the MIL
illuminates and a trouble code is stored.
POSSIBLE CAUSES
INTERMITTENT CONDITION
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
O2 SENSOR HEATER OPERATION
O2 SENSOR
EVAP SYSTEM OPERATION
O2 SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
O2 SENSOR SIGNAL CIRCUIT OPEN
TPS VOLTAGE GREATER THAN 0.92 VOLTS WITH THROTTLE CLOSED
TP SENSOR SWEEP
MAP SENSOR OPERATION
ECT SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR (HIGH)
PCM
88
DRIVEABILITY - GAS
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