DTC P0966 Pressure Control Solenoid 2 (PCS2) Control Circuit Low

P0966 - Pressure Control Solenoid 2 

Circuit Description
Pressure Control Solenoid 2 (PCS2) is a normally open solenoid used to apply the C2 clutch in fourth through sixth range and the C3 clutch in reverse. The TCM commands the solenoid OFF to produce hydraulic pressure in the clutch apply circuit. When PCS2 is commanded ON, the C2 clutch is released.

The TCM sends control current to PCS2 from High Side Driver 2 (HSD2) via wire 171. HSD2 is continuously ON unless the TCM detects a fault condition. The Transmission Control Module (TCM) regulates the amount of current to PCS2 by switching PCS2 Low Side Driver (LSD) ON and OFF. Wire 152 completes the circuit between PCS2 and its LSD. DTC P0966 indicates that the TCM has detected a short-to-ground condition in the low side of PCS2 electrical circuit.

Conditions for Running the DTC
• The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater than 9V and less than 32V (24V TCM).
• TCM initialization is in process or engine speed is greater than 200 rpm and less than 7500 rpm for 5 seconds.

Conditions for Setting the DTC
DTC P0966 sets when the TCM detects a short-to-ground in the PCS2 return circuit for more than 2 seconds.

Actions Taken When the DTC Sets
When DTC P0966 is active, the following conditions occur:
• The CHECK TRANS light illuminates.
• DTC is stored in TCM history.
• Hydraulic default (SOL OFF) is commanded. The shift selector position and hydraulic state of latch valves determines the range attained.

Conditions for Clearing the DTC/CHECK TRANS Light
Use the Allison DOC™ For PC–Service Tool to clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids
• DTC P0966 indicates a short-to-ground in the electrical circuit for the PCS2 solenoid.
• You may have to drive the vehicle in order to experience a fault. Use the data obtained from failure records to determine transmission range and/or certain vehicle operating variables such as temperature, run time etc. This data can be useful in reproducing the failure mode when DTC was set.
• Inspect the wiring for poor electrical connections at the TCM and transmission connector. Look for the following conditions:
→A bent terminal
→A backed-out terminal
→A damaged terminal
→Poor terminal tension
→A chafed wire
→A broken wire inside the insulation
• Inspect OEM wiring harness routing, look for possible contact points where chafing could occur leading to an open or short circuit condition. Moving parts on the vehicle could be contacting  harness; this includes parking brake drum, suspension components, etc.
• When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
• Advanced Troubleshooting (requires a frequency-capable digital multimeter, if available), measure solenoid LSD functionality as follows:
1. Install TCM breakout harness adapter J 47275 between the 80-way connectors of the TCM and OEM
2. Set up a frequency-capable digital multimeter, such as Fluke 87, to monitor frequency by selecting the VOLTS-DC scale and pressing the HERTZ button once.
3. Connect the RED test lead to the solenoid low side pin at TCM breakout harness adapter J 47275. Connect the BLACK test lead to the isolated ground pin.
4. Use Allison DOC™ For PC–Service Tool solenoid test function to command the solenoid ON and OFF. Read More: Solenoid Test using ALLISON DOC Software (ALLISON Transmission).
5. Frequency should read in the KILOHERTZ range when the driver is commanded ON. Frequency should read 0 hertz when the driver is commanded OFF.

#Test Description
This DTC requires the use of the J 47275 TCM Breakout and J 47279 Transmission Breakout. The numbers below
refer to step numbers on the diagnostic table.
2. Tests for the proper ignition voltage.
→Install the Allison DOC™ For PC–Service Tool.
→Start the Engine.
→Record the failure records.
→Monitor ignition voltage. Is the voltage within the specified values? 9–18V for 12V TCM, and 18–32V for 24V TCM.
3. Tests for an active DTC.
→Clear the DTC.
→Start the Engine and test drive the vehicle.
→Attempt to duplicate the same conditions observed in the failure records (range attained, temperature, etc.). NOTE: This DTC detects a short-to-ground condition in the PCS2 electrical circuit. Did DTC P0966 return?
4. Tests for wire-to-wire shorts or a short-to-ground condition in wire 152.
→Turn ignition OFF.
→Disconnect the TCM 80-way connector.
→Install the OEM-side of the 80-way connector to the J 47275 TCM Breakout. Leave the TCM disconnected.
→Disconnect the transmission 20-way connector.
→Inspect the routing of wire 152 in the chassis harness between the TCM and transmission
→At J 47275-1 TCM Overlay, test for wire-to-wire shorts between pin 52 and all other pins in the 80 way connector, and short-to-ground between pin 52 and chassis ground. Were any wire-to-wire shorts or shorts-to-ground wiring defects found?
6. Tests for the wire-to-wire shorts or a short-to-ground in the internal transmission harness.
→Turn ignition OFF.
→Install J 47279 Transmission Breakout to transmission 20-way connector. Leave the OEM harness disconnected.
→Using a DVOM, test for wire-to-wire shorts between pin 5 and pin 6 of the 20-way connector, or shorts-to-ground between pin 5 and chassis ground. NOTE: The resistance value between pins 5 and 6 will read normal solenoid resistance (4.0 to 7.8 ohms). The resistance between pins 5 and 4, between 5 and 9, and between pins 5 and 10 will be twice normal solenoid resistance. Were any wire-to-wire shorts or shorts-to-ground found?
7. Remove the hydraulic control module assembly.
→Inspect the internal harness for wire-to-wire shorts or shorts-to-ground. Were any wire-to-wire shorts or shorts-to-ground found?
→Repair or replace the internal wiring harness. Is the repair complete?
→Replace PCS2. Is the replacement complete? NOTE: In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM.

To verify the repair:
1. Clear the DTC.
2. Drive the vehicle under normal operating conditions.
Did the DTC return?

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