1.
2.

Replace the internal transmission wire
harness (refer to the Service Manual or
In-Chassis Maintenance).
Is the replacement complete?

Is the replacement complete?
15

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 P0965 active after reprogramming the
TCM?

Begin diagnosis
again. Go to
Step 1

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

Go to Step 16

SIL 14-TR-18
September, 2018
Page 30 of 72

DTC P0965 Pressure Control Solenoid 2 (PCS2) Control
Circuit—Performance (cont'd)
Step
16

Action
1.
2.
3.
4.

5.

6.

Turn ignition OFF.
Install test a TCM and torque bolt in 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 TCM input wire 162.
If codes are not active with test TCM
installed, then turn ignition OFF and
re-install the original TCM.
Restart engine and check again for active
DTCs.

Value(s)

Yes

No

Go to Step 17

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?
17

To verify the repair:
1. Clear the DTC
2. Drive the vehicle under circumstances
shown in the failure records.
Did DTC P0965 return?

Begin the
diagnosis again.
Go to Step 1

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

Repair complete.

SIL 14-TR-18
September, 2018
Page 31 of 72

DTC P2534 Ignition Switch Run/Start—Circuit Low

Circuit Description
This DTC is set when the TCM detects if the Run/Start wired input to the TCM is low when it is expected to be high.
DTC P2534 indicates that the TCM processor has detected low and open conditions in the ignition switch run/start
electrical circuit. Open, short to ground or wire to wire short conditions may exist in the ignition switch run/start
circuit (wire 123).
Action Taken When the DTC Sets
When DTC P2534 is active, the following conditions occur:
• The Malfunction Indicator Lamp illuminates on first occurrence.
• The Service Transmission message is displayed in the vehicle message center on the Silverado 4500HD,
5500HD, 6500 HD and the Navistar CV models.
• DTC is stored in the TCM history.
NOTE: When connecting the Allison DOC® software to a General Motors Silverado 4500HD, 5500HD and
6500HD models or a NAVISTAR CV model use the J-48624 Translator and the J-41788 OBD II Connector.
Conditions for Clearing the DTC/CHECK TRANS Light
Use the Allison DOC® software 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 failure.
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 the Use J-39700 Universal Breakout Box, the appropriate harness adapters, 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 and J-48624

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

SIL 14-TR-18
September, 2018
Page 32 of 72

DTC P2534 Ignition Switch Run/Start—Circuit Low (cont'd)
Translator and J-41788 OBD II Connector with the Allison DOC® software 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.
• You may have to drive the vehicle in order to experience a fault.
• This DTC indicates a variation in ignition voltage. Common ignition circuit problems for this DTC are a fault in
the feed wires to the TCM, a defective ignition switch, or a large vehicle accessory load on the ignition circuit.
• A vehicle charging system failure may cause this DTC to set under certain circumstances.
• This DTC may indicate that an internal voltage problem has occurred inside the TCM. The use of a substitute
TCM would be a good way to diagnose this problem.
• A defective vehicle battery may induce this DTC.
• Inspect the wiring for poor electrical connections at the TCM. 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
• When diagnosing for an intermittent short or open circuit condition, massage the wiring harness while
watching the test equipment for a change.
Tool Requirements:
• Allison DOC® software
• 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 tests for an active DTC.
3. This step tests for voltage at pin 23.
5. This step test for open condition in OEM wire harness.
6. This step test for wire to wire shorts in the OEM wire harness.
7. This step test for shorts to ground in the OEM wire harness.
10. Recalibrate TCM with updated version of original calibration.
11. Install test TCM.

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

SIL 14-TR-18
September, 2018
Page 33 of 72

DTC P2534 Ignition Switch Run/Start—Circuit Low (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
DOC®

Value(s)

Yes

No

1

Connect the Allison
software.
Start engine.
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

2

1.
2.

Go to Step 3

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

1.
2.
3.

Clear the DTC.
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, short to ground or wire to wire shorts
in the Ignition Switch Run/Crank Circuit Low
electrical circuit.
Did the DTC return?

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

SIL 14-TR-18
September, 2018
Page 34 of 72

DTC P2534 Ignition Switch Run/Start—Circuit Low (cont'd)
Step

Action

Value(s)

Yes

No

3

Turn ignition OFF.
Connect the TCM Breakout Harness
Adapter to the J-39700 Universal Breakout
Box.
3. Connect the OEM TCM wire harness
80-way connector to the TCM Breakout
Harness.
4. Leave 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 Overlay while cranking the
engine.
Was voltage measured at pin 23?

9-18V (12V TCM)

Go to Step 5

Go to Step 4

4

Check the Transmission Ignition Fuse in the
OEM fuse panel.
Was fuse open?

Check and
replace fuse
47 in the OEM
Underhood
Electrical Center
and repeat
Step 4. Go to
Step 5 if fuse
is OK

Go to Step 5

5

1.
2.

Go to Step 6

Go to Step 8

1.
2.

Turn ignition OFF.
Connect the J-47275 TCM Breakout
Harness Adapter to the J-39700 Universal
Breakout Box.
3. Connect the OEM TCM wire harness
80-way connector to the J-47275 TCM
Breakout Harness Adapter.
4. Leave the TCM disconnected. Do not
connect the TCM side of the Breakout
Harness to the TCM.
5. Disconnect the 24-way connector at
transmission.
6. Using a DVOM, measure between pin 23
on the J-39700 Universal Breakout Box
and the J-47278-1 Transmission 24-way
Magnetic Overlay and pin X103 in the OEM
in-line connector A2.
Was continuity measured?

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

SIL 14-TR-18
September, 2018
Page 35 of 72

DTC P2534 Ignition Switch Run/Start—Circuit Low (cont'd)
Step

Action

Value(s)

Yes

No

6

1.
2.

Turn ignition OFF.
Connect the J-47275 TCM Breakout
Harness Adapter TCM to the Breakout Box.
3. Connect the OEM TCM wire harness
80-way connector to the J-47275 TCM
Breakout Harness Adapter.
4. Leave the TCM disconnected. Do not
connect the TCM side of the Breakout
Harness to the TCM.
5. Disconnect the 24-way connector at
transmission.
6. Using a Digital volt/ohmeter (DVOM), test
for short to ground between pin 23 and all
other pins on the J-47275-1 TCM Overlay.
Was continuity measured?

Go to Step 7

Go to Step 8

7

1.
2.

Turn ignition OFF.
Disconnect the 80-way TCM connector
and install the 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 pin 23 to chassis ground on the
J-47275-1 TCM Overlay.
Was continuity measured between this pin and
to chassis ground?

Go to Step 8

Go to Step 12

8

Repair the vehicle wiring harness.

Go to Step 12

Go to Step 9

Go to Step 11

Go to Step 12

NOTE: The vehicle OEM has responsibility for
all external wiring. The OEM should perform.
Is the repair complete?
9

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

10

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 P2543 active after reprogramming the
TCM?

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

SIL 14-TR-18
September, 2018
Page 36 of 72

DTC P2534 Ignition Switch Run/Start—Circuit Low (cont'd)
Step
11

Action
1.
2.
3.
4.

5.

6.

Turn ignition OFF.
Install test a TCM and torque bolt in TCM to
2.0-3.2 N·m (18-28 lb in).
Start the engine and apply and release
service brakes.
Using the Allison DOC® software check for
active codes and monitor service brake
status on TCM input wire 162.
If codes are not active with the test TCM
installed, then turn ignition OFF and
re-install the original TCM.
Restart engine and check again for active
DTCs.

Value(s)

Yes

No

Go to Step 12

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?
12

To verify the repair:
1. Clear the DTC.
2. Drive the vehicle under normal operating
conditions.
3. Using the Allison DOC® software, monitor
the ignition voltage.
4. Drive the vehicle under normal operating
conditions.
Did DTC P2534 return?

Begin the
diagnosis again.
Go to Step 1

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

Repair complete.

SIL 14-TR-18
September, 2018
Page 37 of 72

DTC P2535 Ignition Switch Run/Start—Circuit High

Circuit Description
This DTC is set when the TCM detects if the Run/Start wired input to the TCM is high when it is expected to be low.
DTC P2535 indicates that the TCM processor has detected high condition in the ignition switch run/start electrical
circuit. The short to power or wire to wire short conditions may exist in the ignition switch run/start circuit (wire 123).
Action Taken When the DTC Sets
When DTC P2535 is active, the following conditions occur:
• DTC is stored in the TCM history.
• The Service Transmission message is displayed in the vehicle message center on the Silverado 4500HD,
5500HD, 6500 HD and the Navistar CV models.
Conditions for Clearing the DTC
Use the 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 warmup cycles without failure.
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.
Diagnostic Aids
The following procedures are not documented in any Allison procedures or in any Allison Troubleshooting Manual
or Service Manual and therefore 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 the J-39700 Universal Breakout Box, the appropriate harness adapters, 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 and 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.

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

SIL 14-TR-18
September, 2018
Page 38 of 72

DTC P2535 Ignition Switch Run/Start—Circuit High (cont'd)
– 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.
• You may have to drive the vehicle in order to experience a fault.
• This DTC indicates a variation in ignition voltage. Common ignition circuit problems for this DTC are a fault in
the feed wires to the TCM, a defective ignition switch, or a large vehicle accessory load on the ignition circuit.
• A vehicle charging system failure may cause this DTC under certain circumstances.
• This DTC may indicate that an internal voltage problem has occurred inside the TCM. The use of a substitute
TCM would be a good way to diagnose this problem.
• A defective vehicle battery may induce this DTC.
• Inspect the wiring for poor electrical connections at the TCM. 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
• When diagnosing for an intermittent short or open circuit condition, massage the wiring harness while
watching the test equipment for a change.
Tool Requirements:
• Allison DOC®