Jeep Liberty KJ. Manual — part 472
13.
MAP SENSOR
Turn the ignition off.
Connect the C1 PCM harness connector.
Ignition on, engine not running.
With a scan tool, monitor the MAP Sensor voltage.
Connect a jumper wire between the (K1) MAP Signal circuit and the
(K900) Sensor ground circuit.
Does the scan tool display MAP voltage from approximately 4.9
volts to below 0.5 of a volt with the jumper wire installed?
Yes
>> Replace the MAP Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No
>> Go To 14
NOTE: Remove the jumper wire before continuing.
14.
EXCESSIVE RESISTANCE IN THE (K1) MAP SIGNAL CIRCUIT
Turn the ignition off.
Disconnect the C2 PCM harness connector.
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 (K1) MAP Signal circuit from the MAP
Sensor harness connector to the appropriate terminal of special tool
#8815.
Is the resistance below 5.0 ohms?
Yes
>> Go To 15
No
>> Repair the excessive resistance in the (K1) MAP Signal cir-
cuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
9 - 46
ENGINE ELECTRICAL DIAGNOSTICS
KJ
15.
(K1) MAP SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (K1) MAP Signal cir-
cuit in the MAP Sensor harness connector.
Is the resistance below 100 ohms?
Yes
>> Repair the short to ground in the (K1) MAP Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No
>> Go To 16
16.
EXCESSIVE RESISTANCE IN THE (K900) SENSOR GROUND
CIRCUIT
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 (K900) Sensor ground circuit from the
MAP Sensor harness connector to the appropriate terminal of special
tool #8815.
Is the resistance below 5.0 ohms?
Yes
>> Go To 17
No
>> Repair the excessive resistance in the (K900) Sensor
ground circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
17.
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)
No
>> Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
KJ
ENGINE ELECTRICAL DIAGNOSTICS
9 - 47
P0071-AMBIENT AIR TEMPERATURE SENSOR PERFORMANCE
9 - 48
ENGINE ELECTRICAL DIAGNOSTICS
KJ
Theory of Operation
Ambient Air Temperature Sensor performance looks at the outputs of three temperature sensors and compare them
under cold start conditions. Following a start to run delay time, the outputs of the ambient, engine coolant, and
intake air temperature sensors will be compared. If the engine coolant and intake air temperature sensors agree and
the ambient air temperature does not agree, the ambient air temperature sensor is declared as irrational.
•
When Monitored:
Engine off time is greater than 480 minutes. Ambient temperature is greater than 4 deg C (38 deg F).
•
Set Condition:
After a calibrated amount of cool down time the BCM compares the ECT Sensor, IAT Sensor, and the Ambient
Air Temp Sensor values. If the IAT Sensor value is not within –10 deg C (18 deg F) of the other two temper-
ature sensors. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes
(G31) AAT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
(G31) AAT SIGNAL CIRCUIT OPEN
(K300) SENSOR GROUND CIRCUIT OPEN
(G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND
(G31) AAT SIGNAL CIRCUIT SHORTED TO THE (K300) SENSOR GROUND CIRCUIT
AMBIENT AIR TEMPERATURE SENSOR
CAN C BUS CIRCUITS OPEN OR SHORTED
BCM
BCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.
ACTIVE DTC
NOTE: Diagnose any CAN C Bus communication DTC’s before continuing.
Ignition on, engine not running.
With a scan tool, read DTCs.
Is the DTC active at this time?
Yes
>> Go To 2
No
>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
KJ
ENGINE ELECTRICAL DIAGNOSTICS
9 - 49
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