Jeep Grand Cherokee WJ. Manual - part 638

TEST

ACTION

APPLICABILITY

WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
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 DRB
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 DTC When Monitored and Set Conditions. 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 ROAD TEST VERIFICATION - VER-2.

→

Test Complete.

Turn the ignition off.
Disconnect the Engine Speed Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between ground and the Engine Speed Sensor Signal circuit.
Is the resistance above 100 kohms?

All

Yes

→

Go To

→

Repair the Engine Speed Sensor Signal circuit for a short to
ground.
Perform ROAD TEST VERIFICATION - VER-2.

Turn the ignition off.
Disconnect the Engine Speed Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between the Engine Speed Sensor Signal and Sensor Ground
circuits.
Is the resistance above 100 kohms?

All

Yes

→

Go To

→

Repair the Engine Speed Sensor Signal and Sensor Ground
circuits for a short together.
Perform ROAD TEST VERIFICATION - VER-2.

Turn the ignition off.
Disconnect the Engine Speed Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the Engine Speed Sensor Signal circuit.
Is the resistance below 5.0 ohms?

All

Yes

→

Go To

→

Repair the Engine Speed Sensor Signal circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.

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DRIVEABILITY - DIESEL

P0725-ENGINE SPEED SENSOR DYN. PLAUSIBILITY —

Continued

TEST

ACTION

APPLICABILITY

Turn the ignition off.
Disconnect the Engine Speed Sensor harness connector.
Disconnect the ECM harness connectors.
Turn the ignition on.
Measure the voltage of the Engine Speed Sensor Signal circuit.
Is the voltage below 0.5 volt?

All

Yes

→

Go To

→

Repair the Engine Speed Sensor Signal circuit for a short to
voltage.
Perform ROAD TEST VERIFICATION - VER-2.

NOTE: Ensure the ECM and Engine Speed Sensor harness connectors are
connected.
Connect, by back probing, a voltmeter capable of reading frequency to ECM harness
connector C2 cavity 67.
Crank the engine while monitoring the voltmeter.
Is the frequency between 16 and 20 Hz at 270-300 cranking RPM?

All

Yes

→

Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.

→

Replace the Engine Speed Sensor in accordance with the Service
Information.
Perform ROAD TEST VERIFICATION - VER-2.

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P0725-ENGINE SPEED SENSOR DYN. PLAUSIBILITY —

Continued

Symptom:

P0725-ENGINE SPEED SENSOR OVERSPEED RECOGNITION

When Monitored and Set Condition:

P0725-ENGINE SPEED SENSOR OVERSPEED RECOGNITION

When Monitored:

With the engine running.

Set Condition:

The engine speed sensor signal indicates engine speed is above 5100 RPM

for at least 500 milliseconds. NOTE: Engine damage is possible when the engine speed
exceeds 5100 RPM.

POSSIBLE CAUSES

CHECK FOR OTHER DTCS

ENGINE CONTROL MODULE

REPLACE THE ENGINE SPEED SENSOR

INTERMITTENT CONDITION

TEST

ACTION

APPLICABILITY

CAUTION: Engine damage is possible when engine speed exceeds 5100
RPM.
NOTE: This DTC indicates the Engine Speed Sensor has seen an engine
speed above 5100 RPM.
Turn the ignition on.
With the DRB, check for other Engine Speed Sensor DTCs.
Are other Engine Speed Sensor DTCs present?

All

Yes

→

Refer to symptom list for problems related to other DTCs before
continuing.
Perform ROAD TEST VERIFICATION - VER-2.

→

Go To

Turn the ignition on.
With the DRB, erase ECM DTCs.
Test drive the vehicle and monitor the DRB for ECM DTCs.
Did this DTC reset?

All

Yes

→

Go To

→

Go To

110

DRIVEABILITY - DIESEL

TEST

ACTION

APPLICABILITY

Replace the Engine Speed Sensor in accordance with the Service Information.
With the DRB, erase ECM DTCs.
Perform several drive cycles, turning the ignition off for at least 10 seconds between
each drive cycle.
Monitor the DRB for ECM DTCs.
Did this DTC reset?

All

Yes

→

Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.

→

The repair is complete.
Perform ROAD TEST VERIFICATION - VER-2.

All

Yes

→

Repair as necessary
Perform ROAD TEST VERIFICATION - VER-2.

→

Test Complete.

111

DRIVEABILITY - DIESEL

P0725-ENGINE SPEED SENSOR OVERSPEED RECOGNITION —

Continued

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