• J-39700 Universal Breakout Box
• J-47275 TCM Breakout Harness
• J-47278-1 Transmission Magnetic Overlay
• J-46708 Digital Multimeter
Test Description
The numbers below refer to the step numbers on the diagnostic table:
2. This step checks for active DTCs.
3. This step tests for proper ignition voltage.
4. This step tests for wire to wire shorts in the OEM wiring harness.
7. Recalibrate TCM with updated version of original calibration.
8. Install test TCM.
NOTE: The J-39700 Universal Breakout Box, adapter harnesses, jumpers, and the J-46708
Digital Multimeter leads add a few ohms of resistance to a circuit. Refer to BEGINNING THE
TROUBLESHOOTING PROCESS for the procedure to determine the tool resistance that is added to a
test circuit.

Copyright © 2018 Allison Transmission, Inc. All Rights Reserved.

SIL 14-TR-18
September, 2018
Page 39 of 72

DTC P2535 Ignition Switch Run/Start—Circuit High (cont'd)
NOTE: The Allison Transmission warranty, or the extended coverage for parts and labor, does not cover
the repair or replacement of OEM or bodybuilder-provided components or any external wire harnesses not
provided by Allison Transmission, Inc.
Before repairing or replacing these components or circuits that caused a transmission issue, always
contact the vehicle OEM call center and/or the vehicle OEM or bodybuilder service representative to
verify the warranty coverage and proper payment arrangements, arrange an alternate sublet or repair
plan (if needed), and get troubleshooting assistance for the repair (such as vehicle schematics, DTC
trees, parts assistance, etc.).

Step

Action

1

2

Value(s)

Yes

No

Connect using the Allison DOC® software
with the J-48624 Translator and the J-41788
OBD II Connector
2. Start engine.
3. Using the Allison DOC® software, record
snapshot showing active or inactive
code(s).
4. Review failure records report from snapshot
to determine conditions when DTC occurs.
Is the DTC active?

Go to Step 2

Troubleshoot
any other active
DTCs if present.
If no other DTCs
are active, go
to Step 2

1.
2.
3.

Go to Step 3

System OK.
Clear inactive
DTCs and
return vehicle
to service.

Go to Step 4

Check and
replace fuse
47 in the OEM
Underhood
Electrical Center
and repeat
Step 3. Go to
Step 4 if fuse
is OK

1.

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 is intended to detect an
open condition in the Ignition Switch Run/Start
electrical circuit.
Did the DTC return?
3

1.
2.

Turn OFF the ignition.
Connect J-47275 TCM Breakout Harness
Adapter.
3. Connect the OEM TCM wire harness
80-way connector to the J-39700 Universal
Breakout Box.
4. Leave the TCM disconnected. Do not
connect the TCM side of the Breakout
Harness to the TCM.
5. On the J-39700 Universal Breakout Box,
measure ignition voltage pin 23 on the
J-47275-1 TCM Magnetic Overlay while
cranking the engine
Was voltage measured at pin 23?

9-18V (12V TCM)

Copyright © 2018 Allison Transmission, Inc. All Rights Reserved.

SIL 14-TR-18
September, 2018
Page 40 of 72

DTC P2535 Ignition Switch Run/Start—Circuit High (cont'd)
Step

Action

Value(s)

Yes

No

4

1.
2.

Turn OFF the ignition.
Disconnect the 80-way TCM connector and
install the J-39700 Universal Breakout Box
to the 80-way connector.
3. Disconnect the 24-way transmission
connector and leave disconnected.
4. On the J-39700 Universal Breakout Box,
measure ignition voltage pin 23 to all other
pins on the J-47275-1 TCM Magnetic
Overlay.
Was continuity measured between pin 23 and
any other pin on the Breakout Box?

Go to Step 5

Go to Step 9

5

Repair the vehicle wiring harness.

Go to Step 9

Go to Step 6

Go to Step 9

Replace TCM

Go to Step 8

Go to Step 9

NOTE: The vehicle OEM has responsibility for
all external wiring. The OEM should perform
vehicle harness repairs.
Is the repair complete?
6

NOTE: In most cases the TCM is not at fault.
Investigate thoroughly before replacing the
TCM. Refer to 4-6. TCM Diagnostic Procedure.
Is the replacement complete?

7

1.

If the service outlet is authorized to use
the TCM Reflash software, recalibrate the
original TCM with the latest calibration and
software.
2. Once the TCM recalibration is complete,
use the Allison DOC® software to check for
active DTCs.
Is DTC P2535 active after reprogramming the
TCM?

Copyright © 2018 Allison Transmission, Inc. All Rights Reserved.

SIL 14-TR-18
September, 2018
Page 41 of 72

DTC P2535 Ignition Switch Run/Start—Circuit High (cont'd)
Step
8

Action
1.
2.
3.
4.

5.

6.

Turn ignition OFF.
Install a test TCM and torque bolt in the
TCM to 2.0-3.2 N·m (18-28 lb in).
Start engine and apply and release service
brakes.
Using the Allison DOC® software check for
active codes and monitor service brake
status on the TCM input wire 123.
If codes are not active with test the TCM
installed, then turn ignition OFF and
re-install original the TCM.
Restart the engine and check again for
active DTCs.

Value(s)

Yes

No

Go to Step 9

NOTE: In most cases, the TCM is not at
fault. Investigate thoroughly before replacing
the TCM. Refer to 4-6 TCM DIAGNOSTIC
PROCEDURE.
Is repair or replacement complete?
9

To verify the repair:
1. Clear the DTC.
2. Drive the vehicle under normal operating
conditions.
3. Using the J-48624 Translator device with
the J-41788 OBD II Connector, monitor
the ignition voltage with the Allison DOC®
software.
4. Drive the vehicle under normal operating
conditions.
Did DTC P2535 return?

Begin Diagnostic
again. Go to
Step 1

Copyright © 2018 Allison Transmission, Inc. All Rights Reserved.

Repair complete.

SIL 14-TR-18
September, 2018
Page 42 of 72

DTC P2728 Pressure Control Solenoid 1 (PCS1) Control
Circuit—Performance

Circuit Description
PCS1 is a Pressure Proportional to Current (PPC) solenoid used to control oncoming and off-going and holding
pressure to any one of five clutches.
The TCM sends control current to PCS1 from High Side Driver 1 (HSD1) via wire 111. HSD1 is continuously on
unless the TCM detects a fault condition. The TCM regulates the amount of current to PCS1 by switching the low
side driver on and off. Wire 155 completes the circuit between PCS1 and its low side driver. DTC P2728 indicates
that the TCM processor has detected an open, short to ground, short to power or wire to wire shorts condition in
the electrical circuit. The open condition may exist in the high side (wire 111) or low side (wire 155).
This test detects the performance of the solenoid by comparing desired current to current as measured by the
control integrated circuit.
Actions Taken When the DTC Sets
When DTC P2728 is active, the following conditions occur:
• If the failure occurs while in a forward range, a shift to 1st, 3rd, or 5th range is made.
• While diagnostic response is active, if shift selector is moved to N (Neutral), transmission shifts to neutral;
if the shift selector is moved to R (Reverse), transmission shifts to reverse. If the shift selector is moved
Copyright © 2018 Allison Transmission, Inc. All Rights Reserved.

SIL 14-TR-18
September, 2018
Page 43 of 72

DTC P2728 Pressure Control Solenoid 1 (PCS1) Control
Circuit—Performance (cont'd)
to D (Drive) or R (Reverse) from the range failed in, the transmission will shift to the requested range
if transmission operating conditions allow. If the shift selector is moved to N (Neutral), the transmission
will shift to neutral.
• The Service Transmission message is displayed in the vehicle message center on the Silverado 4500HD,
5500HD, 6500 HD and the Navistar CV models.
• The Malfunction Indicator Lamp (MIL) illuminates on first occurrence.
• The TCM forces Variable Modulated Main off.
• The DTC is stored in the TCM history.
NOTE: When connecting Allison DOC® to a General Motors Silverado 4500HD, 5500HD and 6500HD
models or a NAVISTAR CV model use J-48624 Translator and J-41788 OBD II Connector.
Conditions for Clearing the DTC
Use Allison DOC® 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 the DTC recurring.
Diagnostic Aids
The following procedures are not documented in any Allison procedures or in any Allison Troubleshooting
Manual or Service Manual and should not be used as a method to diagnose any transmission DTCs, function,
or shift quality concern:
– Back-probing any connections used for transmission features or functions may damage and/or unlock
terminals from the back-probed connector creating permanent or intermittent shorts and/or open circuits.
If possible, use J-39700 Universal Breakout Box, J-48624 Translator and J-41788 OBD II Connector, and
appropriate magnetic overlays to troubleshoot the vehicle.
– Load-testing any transmission-related circuits with any other electrical devices such as vehicle lamps or
relays, especially with the TCM connected to the harness. Use J-39700 Universal Breakout Box, J-48624
Translator and J-41788 OBD II Connector with Allison DOC® to monitor the circuit performance in question
unless otherwise specified in the various Troubleshooting Manuals.
– Piercing a wire to check for voltages, shorts-to-grounds or other wires anywhere in the circuit but especially
at the TCM. This creates a leak path for moisture and damages the wire and insulation.
An intermittent circuit condition can allow this DTC to set. Make sure you check for the following conditions at the
OEM harness first, then at the transmission internal harness:
• DTC P2728 indicates an open, short to ground, short to power or wire to wire shorts in the electrical circuit
for the PCS1.
• Inspect the wiring for poor electrical connections at the TCM and the transmission main connector. Look for
the following conditions:
– A bent terminal.
– A backed-out terminal.
– A damaged terminal.

Copyright © 2018 Allison Transmission, Inc. All Rights Reserved.

SIL 14-TR-18
September, 2018
Page 44 of 72

DTC P2728 Pressure Control Solenoid 1 (PCS1) Control
Circuit—Performance (cont'd)
– 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 circuit condition. Moving parts on the vehicle could be contacting the harness; this includes parking
brake drum, suspension components, transmission shift linkage, etc.
• When diagnosing for an intermittent open condition, massage the wiring harness while watching the test
equipment for a change. It may be necessary to check continuity at individual wires within a harness to
isolate an intermittent circuit ground condition.
• 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 the DTC was set.
Tool Requirements:
• Allison DOC®
• J-39700 Universal Breakout Box
• J-47275 TCM Breakout Harness
• J-47275-1 TCM Magnetic Overlay
• J-47278-1 Transmission Magnetic Overlay
• J-46708 Digital Multimeter
Test Description
The numbers below refer to the step numbers on the diagnostic table.
1. This step tests for the proper ignition voltage.
4 This step tests the OEM harness for an open condition in either wire 111 or wire 155 of the OEM chassis
harness.
5 This step tests the OEM harness for a wire to wire shorts condition in either wire 111 or wire 155 of the
OEM chassis harness.
6 This step tests the OEM harness for a short to ground condition in either wire 111 or wire 155 of the
OEM chassis harness.
7 This step tests the OEM harness for a short to power condition in either wire 111 or wire 155 of the
OEM chassis harness.
8. Repair of the OEM chassis wiring harness
9 This step tests for wire to wire shorts in the transmission internal wire harness.
10This step tests for short to ground in the transmission internal wire harness.
11 This step checks the resistance of PCS1.
15. Recalibrate TCM with updated version of original calibration.
16. Install a test TCM.

Copyright © 2018 Allison Transmission, Inc. All Rights Reserved.

SIL 14-TR-18
September, 2018
Page 45 of 72

DTC P2728 Pressure Control Solenoid 1 (PCS1) Control
Circuit—Performance (cont'd)
NOTE: The J-39700 Universal Breakout Box, adapter harnesses, jumpers, and the J-46708
Digital Multimeter leads add a few ohms of resistance to a circuit. Refer to BEGINNING THE
TROUBLESHOOTING PROCESS for the procedure to determine the tool resistance that is added to a
test circuit.

NOTE: The Allison Transmission warranty, or the extended coverage for parts and labor, does not cover
the repair or replacement of OEM or bodybuilder-provided components or any external wire harnesses not
provided by Allison Transmission, Inc.
Before repairing or replacing these components or circuits that caused a transmission issue, always
contact the vehicle OEM call center and/or the vehicle OEM or bodybuilder service representative to
verify the warranty coverage and proper payment arrangements, arrange an alternate sublet or repair
plan (if needed), and get troubleshooting assistance for the repair (such as vehicle schematics, DTC
trees, parts assistance, etc.).

Step

Action

1

Was BEGINNING THE TROUBLESHOOTING
PROCESS performed?

2

Connect using the Allison DOC® software
with the J-48624 Translator and the J-41788
OBD II Connector.
2. Start the engine.
3. Record the DTC failure record data.
4. Monitor the ignition voltage.
Is the voltage within the specified values?

3

1.
2.
3.

1.

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.).

Value(s)

9–18V

Yes

No

Go to Step 2

Go to
BEGINNING
THE TROUBLE
SHOOTING
PROCESS

Go to Step 3

Resolve voltage
problem. (Refer
to System
Voltage Low and
System Voltage
High)

Go to Step 5

Go to Diagnostic
Aids

NOTE: This DTC is intended to detect an open,
short to ground, short to power or wire to wire
shorts condition in the PCS1 electrical circuit.
Did DTC return?

Copyright © 2018 Allison Transmission, Inc. All Rights Reserved.

SIL 14-TR-18
September, 2018
Page 46 of 72

DTC P2728 Pressure Control Solenoid 1 (PCS1) Control
Circuit—Performance (cont'd)
Step

Action

Value(s)

Yes

No

4

1.
2.

Turn OFF the ignition.
Install the J-47275 TCM Connector
Breakout Harness and the J-39700
Universal Breakout Box on the TCM 80-way
vehicle wiring harness connector. Leave
TCM disconnected.
3. Remove the 24-way connector from the
transmission. At the 24-way transmission
harness connector install a jumper wire
from pin 14 and 15, leave transmission
disconnected.
4. At the TCM J-39700 Universal Breakout
Box, measure pins 11 and 55 for continuity.
Did the pins have continuity between them?

Go to Step 8

Go to Step 5

5

NOTE: Review TROUBLESHOOTING
OF PERFORMANCE
COMPLAINTSPROCEDURES, before
performing steps.

Go to Step 8

Go to Step 6

Go to Step 8

Go to Step 7

1.
2.
3.

Turn OFF the ignition.
Disconnect the TCM 80-way connector.
Install the OEM side 80-way connector to
the J-39700 Universal Breakout Box. Leave
the TCM disconnected.
4. Remove the jumper wire and leave
the 24-way transmission connector
disconnected.
5. At the J-39700 Universal Breakout Box,
test for wire to wire continuity between pins
11 and 55 to all other pins in the 80-way
connector.
Wire to wire continuity indicates a short between
OEM chassis wiring harness wires. Was
continuity measured?
6

1.
2.

Turn ignition OFF.
Install the J-47275 TCM Breakout Harness
Adapter and J-39700 Universal Breakout
Box on the 80-way OEM connector. Leave
TCM disconnected.
3. Disconnect the 24-way transmission
connector.
4. On the J-39700 Universal Breakout Box
measure continuity between pins 11 and 55
to chassis ground.