Jeep Grand Cherokee WK. Manual — part 1041
P0850-PARK/NEUTRAL SWITCH PERFORMANCE (CONTINUED)
For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS).
For a complete wiring diagram Refer to Section 8W.
Theory of Operation
The Park Neutral switch rationality test is enabled only for vehicles equipped with a 4/5 speed automatic transmis-
sion. This diagnostic checks if the park/neutral switch is incorrectly stuck in the neutral position during driving con-
ditions by comparing Vehicle Speed, Engine Speed, Throttle Position, and Pressure Ratio to the fail thresholds and
by looking at the state of the Park/Neutral Switch. The stuck in drive condition is not explicitly checked as the starter
relay does not energize and therefore render the vehicle inoperable.
•
When Monitored:
Continuously with the transmission in Park, Neutral, or Drive and NOT in Limp-in mode.
•
Set Condition:
This code will set if the PCM detects an incorrect Park/Neutral switch state for a given mode of vehicle oper-
ation. One trip fault. Three good trips to turn off the MIL.
Possible Causes
TRS (T41) SENSE (P/N SENSE) CIRCUIT OPEN
TRS (T41) SENSE (P/N SENSE) CIRCUIT SHORTED TO GROUND
TRANSMISSION RANGE SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.
P/N & D/R NOT IN CORRECT POSITION
NOTE: Check the TCM for DTCs, if P0706 is set in the TCM diagnose the TCM code before continuing.
Ignition on, engine not running.
With the scan tool, read the Park/Neutral Position Switch input state.
While moving the gear selector through all gear positions (Park to 1 and back to Park), monitor the scan tool dis-
play.
Did the scan tool display show P/N and D/R in the correct gear positions?
Yes
>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
>> Go To 2
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ENGINE ELECTRICAL DIAGNOSTICS
WK
P0850-PARK/NEUTRAL SWITCH PERFORMANCE (CONTINUED)
2.
TRS (T41) SENSE (P/N SENSE) CIRCUIT OPEN
Turn the ignition off.
Disconnect the C3 PCM harness connector.
Disconnect the Transmission Range Sensor 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 TRS (T41) Sense (P/N Sense) circuit
from the TRS harness connector to the appropriate terminal of special
tool #8815.
Is the resistance below 5.0 ohms?
Yes
>> Go To 3
No
>> Repair the open in the TRS (T41) Sense (P/N Sense) cir-
cuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)
3.
TRS (T41) SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the TRS (T41) Sense
(P/N Sense) circuit at the TRS harness connector.
Is the resistance above 100k ohms?
Yes
>> Go To 4
No
>> Repair the short to ground in the TRS (T41) Sense (P/N
Sense) circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)
WK
ENGINE ELECTRICAL DIAGNOSTICS
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P0850-PARK/NEUTRAL SWITCH PERFORMANCE (CONTINUED)
4.
TRANSMISSION RANGE SENSOR
Measure the resistance between ground and the (T41) TRS Sense
(P/N Sense) circuit while moving the gear selector through each gear
in the TRS connector.
NOTE: The circuit is grounded in Park and Neutral and open in
the other positions.
Did the resistance change from above 100 kohms (open) to
below 10.0 ohms (grounded)?
Yes
>> Go To 5
No
>> Replace the Transmission Range Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)
5.
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)
9 - 762
ENGINE ELECTRICAL DIAGNOSTICS
WK
P1115-GENERAL TEMPERATURE RATIONALITY
WK
ENGINE ELECTRICAL DIAGNOSTICS
9 - 763
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