Jeep Liberty KJ. Manual - part 470

(K399) O2 2/2 HEATER CONTROL CIRCUIT

Ignition on, engine not running.

With a scan tool, actuate the O2 2/2 Heater Test with the Sensor har-
ness connector still disconnected.

Using a 12-volt test light connected to ground, probe the (K399) O2 2/2
Heater Control circuit in the O2 Sensor harness connector.

Does the test light illuminate brightly and flash on and off dur-
ing the actuation?

Yes

>> Go To 4

>> Go To 5

(Z42) O2 HEATER GROUND CIRCUIT OPEN

Turn the ignition off.

Measure the resistance between an engine ground and the (Z42) O2
2/2 Heater ground circuit in the O2 Sensor harness connector.

Is the resistance below 5.0 ohms?

Yes

>> Replace the O2 Sensor.

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

>> Repair the open in the (Z42) O2 2/2 Heater ground circuit.

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

(K399) O2 2/2 HEATER CONTROL CIRCUIT SHORTED TO BATTERY VOLTAGE

Turn the ignition off.

Disconnect the C3 PCM harness connector.

Ignition on, engine not running.

Using a 12-volt test light connected to ground, probe the (K399) O2
Heater 2/2 Control circuit in the O2 Sensor harness connector.

Does the test light illuminate?

Yes

>> Repair the short to battery voltage in the (K399) O2 2/2

Heater Control circuit.

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

>> Go To 6

9 - 38

ENGINE ELECTRICAL DIAGNOSTICS

(K399) O2 2/2 HEATER CONTROL CIRCUIT OPEN

Turn the ignition off.

CAUTION: Do not probe the PCM harness connectors. Probing the
PCM harness connectors will damage the PCM terminals resulting
in poor terminal to pin connection. Install Miller Special Tool #8815
to perform diagnosis.
Measure the resistance of the (K399) O2 2/2 Heater Control circuit from
the O2 Sensor harness connector to the appropriate terminal of special
tool #8815.

Is the resistance below 5.0 ohms?

Yes

>> Go To 7

>> Repair the open in the (K399) O2 2/2 Heater Control circuit.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to
8 - ELECTRICAL/ELECTRONIC CONTROL MODULES/
POWERTRAIN CONTROL MODULE - DIAGNOSIS AND
TESTING)

PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.

Were there any problems found?

Yes

>> Repair as necessary.

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

>> Replace and program the Powertrain Control Module per Service Information.

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

ENGINE ELECTRICAL DIAGNOSTICS

9 - 39

P0068-MANIFOLD PRESSURE/THROTTLE POSITION CORRELATION

For a complete wiring diagram Refer to Section 8W.

Theory of Operation

This DTC sets when an unexpected high intake manifold air flow condition exists that can lead to increased engine
speed and puts the NGC into a High Air flow Protection limiting mode. The High Air flow Protection feature includes
RPM limits for when a Throttle and/or MAP sensor limp-in fault is present.

•

When Monitored:
During all drive modes.

•

Set Condition:
If vacuum drops below 1.5

Hg with engine RPM greater than 2000 RPM and closed throttle. This fault can set

due to a TPS/MAP sensor failure. It will set much faster than the TPS/MAP fault can mature. If there is not an
obvious large intake leak, suspect a TPS/MAP fault. One Trip Fault. Three good trips to turn off the MIL.

Possible Causes

VACUUM LEAK

RESISTANCE IN THE (F856) 5-VOLT SUPPLY CIRCUIT

(F856) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND

RESISTANCE IN THE (K1) MAP SIGNAL CIRCUIT

(K1) MAP SIGNAL CIRCUIT SHORTED TO GROUND

RESISTANCE IN THE (F855) 5-VOLT SUPPLY CIRCUIT

(F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND

RESISTANCE IN THE (K22) TP SENSOR NO.1 SIGNAL CIRCUIT

(K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO GROUND

RESISTANCE IN THE (K900) SENSOR GROUND CIRCUIT

MAP SENSOR

THROTTLE POSITION SENSOR

PCM

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

Diagnostic Test

ACTIVE DTC

NOTE: Diagnose any TP Sensor or MAP Sensor component DTCs before continuing.

NOTE: If the P0501 - No Vehicle Speed Signal is set long with this DTC, refer to the P0501 diagnostics
before continuing.

NOTE: The throttle plate and linkage should be free from binding and carbon build up.

NOTE: Make sure the throttle plate is at the idle position.
Ignition on, engine not running.

With a scan tool, read DTCs.

Is the DTC active at this time?

Yes

>> Go To 2

>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

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

9 - 40

ENGINE ELECTRICAL DIAGNOSTICS

VACUUM LEAK

NOTE: This code is enabled on engines with a plastic intake manifold and is intended to shut down the
engine if a large crack occurs.

NOTE: A large vacuum leak is most likely the cause of this DTC.
Inspect the Intake Manifold for leaks and cracks.

Inspect the Power Brake Booster for any vacuum leaks.

Inspect the PCV system for proper operation and vacuum leaks.

Inspect the throttle plate to see if it is bent and will close entirely, if it is bent it may need to be replaced.

Inspect the MAP Sensor for proper installation.

Verify the engine is free from any mechanical failures.

Were any vacuum leaks found?

Yes

>> Repair the vacuum leak as necessary.

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

>> Go To 3

MAP SENSOR OPERATION

Start the engine.

With a scan tool, monitor the MAP Sensor voltage.

Snap the throttle.

Does the MAP Sensor voltage vary from below 2.0 volts at idle to above 3.5 volts at wide open throt-
tle?

Yes

>> Go To 4

>> Go To 11

TP SENSOR OPERATION

Ignition on, engine not running.

With a scan tool, monitor the TP Sensor voltage while slowly pressing the throttle pedal from closed to wide open
throttle.

Does voltage start at approximately 0.8 of a volt and go above 3.5 volts with a smooth transition?

Yes

>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

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

>> Go To 5

ENGINE ELECTRICAL DIAGNOSTICS

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