Jeep Grand Cherokee WJ. Manual - part 975

TEST

ACTION

APPLICABILITY

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.

→

Go To

If there are no possible causes remaining, view repair.

All

Repair

Replace and program the Powertrain Control Module in accor-
dance with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER - 5.

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

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.

→

Test Complete.

117

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

THROTTLE POSITION SENSOR SWEEP

MAP SENSOR OPERATION

ECT SENSOR OPERATION

ENGINE MECHANICAL PROBLEM

FUEL FILTER/PRESSURE REGULATOR (HIGH)

PCM

118

DRIVEABILITY - GAS

TEST

ACTION

APPLICABILITY

NOTE: Check for contaminates that may have damaged the O2 Sensor:
contaminated fuel, unapproved silicone, oil and coolant.
Turn the ignition on.
With the DRBIII

t, read DTC’s.

Is the Good Trip counter for this DTC displayed and equal to zero?

All

Yes

→

Go To

→

Go To

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.
Install a fuel pressure gauge to the fuel rail.
Turn the ignition on.
With the DRBIII

t, actuate the ASD Fuel System test and observe the fuel pressure

gauge.
NOTE: Fuel pressure specification is 339 KPa +/- 34 KPa (49.2 psi +/- 5 psi).
Turn the ignition off.
Choose a conclusion that best matches your fuel pressure reading.

All

Below Specification

Go To

Within Specification

Go To

Above Specification

Test Complete.

Caution: Stop All Actuations.

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.
Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module.
Install special 5/16 fuel line adapter tool #6539 or #6631 between disconnected fuel
line and the fuel pump module.
Attach a fuel pressure test gauge to the T fitting on tool #6539 or #6631.
Turn the ignition on.
With the DRBIII

t, actuate the ASD Fuel System test and observe the fuel pressure

gauge.
NOTE: Fuel pressure specification is 339 KPa +/- 34 KPa (49.2 psi +/- 5 psi).
Is the fuel pressure within specification?

All

Yes

→

Repair or replace fuel supply line as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 5.

→

Go To

Caution: Stop All Actuations.

119

DRIVEABILITY - GAS

P0172-1/1 FUEL SYSTEM RICH —

Continued

TEST

ACTION

APPLICABILITY

All

Yes

→

Replace the Fuel Pump Inlet Strainer.
Perform POWERTRAIN VERIFICATION TEST VER - 5.

→

Go To

If there are no possible causes remaining, view repair.

All

Repair

Replace the Fuel Pump Module.
Perform POWERTRAIN VERIFICATION TEST VER - 5.

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

→

Go To

→

Go To

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.

→

Go To

NOTE: The engine must be at operating temperature and in closed loop to
perform this test.
Start the engine.
Allow the engine to reach normal operating temperature.
With the DRBIII

t select System Tests, perform the Purge Vapors Test.

Observe the Short Term Adaptive value and press 3 to flow.
NOTE: Short Term Adaptive value change.
Did the Short Term Adaptive value change?

All

Yes

→

Go To

→

Refer to the Driveability category and perform the appropriate
symptomm.
Perform POWERTRAIN VERIFICATION TEST VER - 5.

120

DRIVEABILITY - GAS

P0172-1/1 FUEL SYSTEM RICH —

Continued

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