DTC P0851 or P0852
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Perform
the Diagnostic
System Check - Vehicle prior to using this diagnostic procedure. |
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Review
Strategy
Based Diagnosis for an overview of the diagnostic approach. |
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Diagnostic
Procedure Instructions provides an overview of each diagnostic category. |
DTC P0851:
Park/Neutral Position (PNP) Switch Circuit Low Voltage
DTC P0852: Park/Neutral Position (PNP) Switch Circuit
High Voltage
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Circuit |
Short to Ground |
Open/High Resistance |
Short to Voltage |
Signal Performance |
|
Park/Neutral Signal |
P0851 |
P0852 |
P0852 |
-- |
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Circuit |
Short to Ground |
Open/High Resistance |
Short to Voltage |
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Operating Conditions: Engine running,
normal operating temperature |
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Park/Neutral Signal |
Park/Neutral |
In-Gear |
In-Gear |
The transmission manual
shift shaft switch assembly, also known as the Internal Mode Switch (IMS),
is a sliding contact switch attached to the manual shift shaft inside the
transmission case. The Park/Neutral Position (PNP) Switch is integrated
into the IMS and connects to the Transmission Control Module (TCM)
lead-frame through a short wire harness. The 5 inputs to the TCM from the
transmission manual shift shaft switch assembly indicate the transmission gear
selector lever position. This information is used for engine start enable,
engine controls as well as determining the transmission shift patterns. The
state of each input is available for display on the scan tool. The five input
parameters represented are Signal A, Signal B, Signal C, Signal P (Parity), and Signal N (Park/Neutral
Start Signal). Park/Neutral Signal is sent from the Park/Neutral switch
directly to the Engine Control Module (ECM) and is used for engine start
enable. The Park/Neutral Signal circuit is not connected to the TCM internally;
the circuit uses the TCM as a pass-through connector only. The ECM Park/Neutral
diagnostic monitors the Park/Neutral Signal circuit to detect Low voltage when
the ECM expects to see High voltage and High voltage when the ECM expects to
see Low voltage.
Conditions
for Running the DTC
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Ignition
voltage is between 9-18 volts. |
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No
TCM DTCs P0601, P0602, P0603, or P0604. |
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No
IMS DTCs P1825 or P1915. |
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No
Communication DTCs U0001, U0100, U0101, U2105, or U2106. |
P0852
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No
TP DTCs P0121, P0122, P0123. |
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No
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No
MAF DTCs P0101, P0102, or P0103. |
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No
MAP DTCs P0106, P0107, or P0108. |
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Engine
Speed is greater than 400 RPM. |
Conditions
for Setting the DTC
P0851
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The
ECM detects the Park/Neutral switch signal equals 0 volts (Low) when the
IMS reports a Drive range for 0.2 seconds. |
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TP
is equal to or greater than 10 percent. |
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Engine
torque is equal to or greater than 75 N·m
(55 lb ft). |
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Vehicle
speed is equal or greater than 10 km/h (6 mph). |
P0852
The ECM detects the
Park/Neutral switch signal equals 12 volts (High) when the IMS reports a
Park/Neutral range for 0.2 seconds.
Action
Taken When the DTC Sets
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DTC
P0851 and P0852 are Type C DTCs. |
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The
ECM uses |
Conditions
for Clearing the DTC
DTC P0851 and P0852 are
Type C DTCs.
Schematic
Reference
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Connector
End View Reference
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DTC
Type Reference
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Electrical
Information Reference
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If there are any other
engine or transmission related DTCs set, diagnose those DTCs first. With a scan
tool observe the Park/Neutral switch parameter in Engine Controls data list and
move the gear shift lever from Park, to Reverse and through all the ranges and
observe the parameter as you move the shift lever. The parameter should display
Park/Neutral when in Park or Neutral and In-Gear when in Reverse, Drive or
Drive Low. It is especially important to closely observe the Park and Neutral
to Drive transitional positions while moving the shift lever and observing for
possible misalignment or slack in the shifter mechanism. If any concerns are
found proceed to Testing.
Disconnect the
transmission 16-way connector and observe the Park/Neutral scan tool parameter
in the Engine Controls data list. The parameter should display In-Gear.
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If
the Park/Neutral parameter does not display In-Gear test the Park/Neutral
signal circuit between the engine side of the transmission 16-way connector
and the ECM connector for a short to ground. |
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If
the Park/Neutral parameter displays In-Gear test the transmission IMS for a
shorted P/N circuit to ground. Inspect the harness for damage or chaffing. |
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If
the IMS was not shorted to ground, test the IMS park/Neutral signal circuit
from the IMS connector on the TCM side to the 16-way connector for an open or
short to ground. |
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If
no concerns are found, replace the ECM. Refer to Control
Module References for replacement, setup, or programming. |
Perform the Control
Solenoid Valve and Transmission Control Module Assembly Inspection .
Perform the Diagnostic
Repair Verification after completing the diagnostic procedure.