Allison

Allison 1000 & 2000 Gen 4 Fault Codes: P0841 Transmission Pressure Switch Solenoid C Circuit Stuck Open

CIRCUIT DESCRIPTION:
The Pressure Switch Manifold (PSM) is a multiple-switch assembly made up of three normally open (N/O) and one normally closed (N/C) pressure switches. The C pressure switch monitors C shift valve positioning and relays it to the TCM. When C pressure switch is in the open state, C shift valve should be in the destroked position.

CONDITIONS FOR RUNNING THE DTC:
1. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater than 18V and less than 32V (24V TCM).
2. DTC P0561, P0562, or P0563 is not active.
3. C shift valve is commanded to the ON (stroked) position.

CONDITIONS FOR SETTING THE DTC:
DTC P0841 is set when C solenoid is commanded ON and C pressure switch status remains OFF for a period of time. The time period is 5 seconds at 0°C (32°F) to -40°C (-40°F). The intent of this DTC is to detect a stuck shift valve, in the destroked state, a mechanical solenoid failure, or an open circuit.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P0841 is active, the following conditions will occur:
1. If the failure occurs while in a forward range, the transmission shifts to 1st, 3rd or 5th range.
2. If the shift selector is moved to N (Neutral), the transmission will shift to neutral.
3. If the shift selector is moved to R (Reverse), the transmission shifts to reverse.
4. If the shift selector is moved to a forward range or reverse and the transmission is compromised by overspeeding or direction change, the transmission shifts to neutral.

DTC P0841 is stored in TCM history.

The CHECK TRANS light illuminates.

The TCM inhibits TCC engagement.

The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
A Scan Tool may be used to clear the code 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:
Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

When a P0841 and P0843 are set in combination, this may indicate an open circuit condition is present at the pressure switch circuit or the shift valve is stuck in the destroked state. See Troubleshooting Process information.

When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. It may be necessary to check for shorting to ground or opens at individual wires within a harness to isolate an intermittent condition. Refer to Wire Check information.

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 where the DTC was set.

Multiple inactive pressure switch DTCs may be due to a plugged Control Main Filter. Ensure that the initial 8000 km (5,000 mile) filter change was performed.

Allison 1000 & 2000 Gen 4 Fault Codes: P0842 Transmission Pressure Switch Solenoid C Circuit Stuck Closed

CIRCUIT DESCRIPTION:
The Pressure Switch Manifold (PSM) is a multiple-switch assembly made up of three normally open (N/O) and one normally closed (N/C) pressure switches. The C pressure switch monitors C shift valve positioning and relays it to the TCM. When C pressure switch is in the open state, C shift valve should be in the destroked position.

CONDITIONS FOR RUNNING THE DTC:
1. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater than 18V and less than 32V (24V TCM).
2. DTC P0561, P0562, or P0563 is not active.
3. C shift valve is commanded to the OFF (destroked) position.

CONDITIONS FOR SETTING THE DTC:
DTC P0842 is set when C solenoid is commanded OFF and C pressure switch status remains ON for a period of time that is temperature dependent. The time period is 2 seconds at 0°C (32°F) or up to 6 seconds at -40°C (-40°F). The intent of this DTC is to detect a stuck shift valve, in the stroked state, a mechanical solenoid failure, or a circuit short to ground.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P0842 is active, the following conditions will occur:
1. If the failure occurs while in a forward range, the transmission shifts to another forward range.
2. If the shift selector is moved to N (Neutral), the transmission will shift to neutral.
3. If the shift selector is moved to R (Reverse), the transmission shifts to reverse.
4. If the shift selector is moved to a forward range or reverse and the transmission is compromised by overspeeding or direction change, the transmission shifts to neutral.

DTC P0842 is stored in TCM history.

The CHECK TRANS light illuminates.

The TCM inhibits TCC engagement.

The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
A Scan Tool may be used to clear the code 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:
Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

When a P0842 and P0840 are set in combination, this may indicate a short to ground at the pressure switch circuit or the shift valve is stuck in the stroked state. See Troubleshooting Process information.

When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. It may be necessary to check for shorting to ground at individual wires within a harness to isolate an intermittent condition. Refer to Wire Check information.

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 where the DTC was set.

Multiple inactive pressure switch DTCs may be due to a plugged Control Main Filter. Ensure that the initial 8000 km (5,000 mile) filter change was performed.

Allison 1000 & 2000 Gen 4 Fault Codes: P0843 Transmission Pressure Switch Solenoid C Circuit High

CIRCUIT DESCRIPTION:
The Pressure Switch Manifold (PSM) is a multiple-switch assembly made up of three normally open (N/O) and one normally closed (N/C) pressure switches. The C pressure switch monitors C shift valve positioning and relays it to the TCM. When C pressure switch is in the open state, C shift valve should be in the destroked position.

CONDITIONS FOR RUNNING THE DTC:
1. Components are powered and the ignition voltage is greater than 5V.
2. DTC P0561, P0562, or P0563 is not active.
3. C shift valve is commanded to the ON (stroked) position.
4. Transmission temperature is above -25°C (-13°F).
5. Vehicle shutdown is not in process.

CONDITIONS FOR SETTING THE DTC:
DTC P0843 sets during steady state operation when C shift valve is in the stroked state (commanded ON) and C pressure switch status is detected as destroked (commanded OFF). Steady state is defined as attaining a valid range. The intent of this code is to detect an open condition in the pressure switch wiring circuit or the pressure switch.

Later software levels incorporate retry logic that allows the TCM to command C solenoid OFF and ON. If the pressure switch state does not change, and remains in the OFF state, DTCs P0841 and P0843 will set.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P0843 is active, the following conditions will occur:
1. If the failure occurs while in a forward range, the transmission shifts to another forward range.
2. If the shift selector is moved to N (Neutral), the transmission will shift to neutral.
3. If the shift selector is moved to R (Reverse), the transmission shifts to reverse.
4. If the shift selector is moved to a forward range or reverse and the transmission is compromised by overspeeding or direction change, the transmission shifts to neutral.

DTC P0843 is stored in TCM history.

The CHECK TRANS light illuminates.

The TCM inhibits TCC engagement.

The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
A Scan Tool may be used to clear the code 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:
Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

When only a DTC P0843 is set, look for an intermittent open condition at the pressure switch circuit or an intermittent hydraulic failure (sticking valve). This code is set when the condition is present more than 3 times during a current drive cycle. See Intermittent Fault information.

When a P0843 and P0841 are set in combination, this may indicate an open circuit condition is present at the pressure switch circuit or the shift valve is stuck in the destroked state. See Troubleshooting Process information.

When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. It may be necessary to check for an open condition at individual wires within a harness to isolate an intermittent condition. Refer to Wire Check information.

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 where the DTC was set.

Multiple inactive pressure switch DTCs may be due to a plugged Control Main Filter. Ensure that the initial 8000 km (5,000 mile) filter change was performed.

Allison 1000 & 2000 Gen 4 Fault Codes: P0845 Transmission Pressure Switch Solenoid D Circuit

CIRCUIT DESCRIPTION:
The Pressure Switch Manifold (PSM) is a multiple-switch assembly made up of three normally open (N/O) and one normally closed (N/C) pressure switches. The D pressure switch monitors D shift valve positioning and relays it to the TCM. When D pressure switch is in the open state, D shift valve should be in the destroked position.

CONDITIONS FOR RUNNING THE DTC:
1. Components are powered and the ignition voltage is greater than 5V.
2. DTC P0561, P0562, or P0563 is not active.
3. D shift valve is commanded to the OFF (destroked) position.
4. Transmission temperature is above -25°C (-13°F).
5. Vehicle shutdown is not in process.

CONDITIONS FOR SETTING THE DTC:
DTC P0845 sets during steady state operation when D shift valve is in the destroked state (commanded OFF) and D pressure switch status is detected as stroked (commanded ON). Steady state is defined as attaining a valid range. The intent of this code is to detect shorts to ground in the pressure switch wiring circuit or the pressure switch.

Later software levels incorporate retry logic that allows the TCM to command D solenoid ON and OFF. If the pressure switch state does not change, and remains in the ON state, DTCs P0845 and P0847 will set.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P0845 is active, the following conditions will occur:
1. If the failure occurs while in a forward range, the transmission shifts to another forward range.
2. If the shift selector is moved to N (Neutral), the transmission will shift to neutral.
3. If the shift selector is moved to R (Reverse), the transmission shifts to reverse.
4. If the shift selector is moved to a forward range or reverse and the transmission is compromised by overspeeding or direction change, the transmission shifts to neutral.

DTC P0845 is stored in TCM history.

The CHECK TRANS light illuminates.

The TCM inhibits TCC engagement.

The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
A Scan Tool may be used to clear the code 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:
Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

When only a DTC P0845 is set, look for an intermittent short to ground at the pressure switch circuit or an intermittent hydraulic failure (sticking valve). This code is set when the condition is present more than 3 times during a current drive cycle. See Intermittent Fault information.

When a P0845 and P0847 are set in combination, this may indicate a short to ground is present at the pressure switch circuit or the shift valve is stuck in the stroked state. See Troubleshooting Process information.

When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. It may be necessary to check for shorting to ground at individual wires within a harness to isolate an intermittent condition. Refer to wire check information.

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.

Multiple inactive pressure switch DTCs may be due to a plugged Control Main Filter. Ensure that the initial 8000 km (5,000 mile) filter change was performed.

Allison 1000 & 2000 Gen 4 Fault Codes: P0848 Transmission Pressure Switch Solenoid D Circuit High

CIRCUIT DESCRIPTION:
The Pressure Switch Manifold (PSM) is a multiple-switch assembly made up of three normally open (N/O) and one normally closed (N/C) pressure switches. The D pressure switch monitors D shift valve positioning and relays it to the TCM. When D pressure switch is in the open state, D shift valve should be in the destroked position.

CONDITIONS FOR RUNNING THE DTC:
1. Components are powered and the ignition voltage is greater than 5V.
2. DTC P0561, P0562, or P0563 is not active.
3. D shift valve is commanded to the ON (stroked) position.
4. Transmission temperature is above -25°C (-13°F).
5. Vehicle shutdown is not in process.

CONDITIONS FOR SETTING THE DTC:
DTC P0848 sets during steady state operation when D shift valve is in the stroked state (commanded ON) and D pressure switch status is detected as destroked (commanded OFF). Steady state is defined as attaining a valid range. The intent of this code is to detect an open condition in the pressure switch wiring circuit or the pressure switch.

Later software levels incorporate retry logic that allows the TCM to command D solenoid OFF and ON. If the pressure switch state does not change, and remains in the OFF state, DTCs P0848 and P0846 will set.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P0848 is active, the following conditions will occur:
1. If the failure occurs while in a forward range, the transmission shifts to another forward range.
2. If the shift selector is moved to N (Neutral), the transmission will shift to neutral.
3. If the shift selector is moved to R (Reverse), the transmission shifts to reverse.
4. If the shift selector is moved to a forward range or reverse and the transmission is compromised by overspeeding or direction change, the transmission shifts to neutral.

DTC P0848 is stored in TCM history.

The CHECK TRANS light illuminates.

The TCM inhibits TCC engagement.

The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
A Scan Tool may be used to clear the code 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:
Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

When only a DTC P0848 is set, look for an intermittent open condition at the pressure switch circuit or an intermittent hydraulic failure (sticking valve). This code is set when the condition is present more than 3 times during a current drive cycle. See Intermittent Fault information.

When a P0848 and P0846 are set in combination, this may indicate an open circuit condition is present at the pressure switch circuit or the shift valve is stuck in the destroked state. See Troubleshooting Process information.

When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. It may be necessary to check for an open condition at individual wires within a harness to isolate an intermittent condition. Refer to Wire Check information.

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.

Multiple inactive pressure switch DTCs may be due to a plugged Control Main Filter. Ensure that the initial 8000 km (5,000 mile) filter change was performed.

Allison 1000 & 2000 Gen 4 Fault Codes: P0870 Transmission Pressure Switch Solenoid E Circuit

CIRCUIT DESCRIPTION:
The Pressure Switch Manifold (PSM) is a multiple-switch assembly made up of three normally open (N/O) and one normally closed (N/C) pressure switches. The E pressure switch monitors E shift valve positioning and relays it to the TCM. When E pressure switch is in the open state, E shift valve should be in the destroked position.

CONDITIONS FOR RUNNING THE DTC:
1. Components are powered and the ignition voltage is greater than 5V.
2. DTC P0561, P0562, or P0563 is not active.
3. E shift valve is commanded to the OFF (destroked) position.
4. Transmission temperature is above -25°C (-13°F).
5. Vehicle shutdown is not in process.

CONDITIONS FOR SETTING THE DTC:
DTC P0870 sets during steady state operation when E shift valve is in the destroked state (commanded OFF) and E pressure switch status is detected as stroked (commanded ON). Steady state is defined as attaining a valid range. The intent of this code is to detect shorts to ground in the pressure switch wiring circuit or the pressure switch.

Later software levels incorporate retry logic that allows the TCM to command E solenoid ON and OFF. If the pressure switch state does not change, and remains in the ON state, DTCs P0870 and P0872 will set.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P0870 is active, the following conditions will occur:
1. If the failure occurs while in a forward range, the transmission shifts to another forward range.
2. If the shift selector is moved to N (Neutral), the transmission will shift to neutral.
3. If the shift selector is moved to R (Reverse), the transmission shifts to reverse.
4. If the shift selector is moved to a forward range or reverse and the transmission is compromised by overspeeding or direction change, the transmission shifts to neutral.

DTC P0870 is stored in TCM history.

The CHECK TRANS light illuminates.

The TCM inhibits TCC engagement.

The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
A Scan Tool may be used to clear the code 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:
Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

When only a DTC P0870 is set, look for an intermittent short to ground at the pressure switch circuit or an intermittent hydraulic failure (sticking valve). This code is set when the condition is present more than 3 times during a current drive cycle. See Intermittent Fault information.

When a P0870 and P0872 are set in combination, this may indicate a short to ground is present at the pressure switch circuit or the shift valve is stuck in the stroked state. See Troubleshooting Process information.

When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. It may be necessary to check for shorting to ground at individual wires within a harness to isolate an intermittent condition. Refer to Wire Check information.

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.

Multiple inactive pressure switch DTCs may be due to a plugged Control Main Filter. Ensure that the initial 8000 km (5,000 mile) filter change was performed.

Allison 1000 & 2000 Gen 4 Fault Codes: P0871 Transmission Pressure Switch Solenoid E Circuit Stuck Open

CIRCUIT DESCRIPTION:
The Pressure Switch Manifold (PSM) is a multiple-switch assembly made up of three normally open (N/O) and one normally closed (N/C) pressure switches. The E pressure switch monitors E shift valve positioning and relays it to the TCM. When E pressure switch is in the open state, E shift valve should be in the destroked position.

CONDITIONS FOR RUNNING THE DTC:
1. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater than 18V and less than 32V (24V TCM).
2. E shift valve is commanded to the ON (stroked) position.

CONDITIONS FOR SETTING THE DTC:
DTC P0871 sets when E solenoid is commanded ON and E pressure switch status remains OFF for a period of time. The time period is 5 seconds at 0°C (32°F) to -40°C (-40°F). The intent of this DTC is to detect a stuck shift valve, in the destroked state, a mechanical solenoid failure, or an open circuit.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P0871 is active, the following conditions will occur:
1. If the failure occurs while in a forward range, the transmission shifts to another forward range.
2. If the shift selector is moved to N (Neutral), the transmission will shift to neutral.
3. If the shift selector is moved to R (Reverse), the transmission shifts to reverse.
4. If the shift selector is moved to a forward range or reverse and the transmission is compromised by overspeeding or direction change, the transmission shifts to neutral.

DTC P0871 is stored in TCM history.

The CHECK TRANS light illuminates.

The TCM inhibits TCC engagement.

The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
A Scan Tool may be used to clear the code 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:
Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

When a P0871 and P0873 are set in combination, this may indicate an open circuit condition is present at the pressure switch circuit or the shift valve is stuck in the destroked state. See Troubleshooting Process information.

When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. It may be necessary to check for an open condition at individual wires within a harness to isolate an intermittent condition. Refer to Wire Check information.

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.

Multiple inactive pressure switch DTCs may be due to a plugged Control Main Filter. Ensure that the initial 8000 km (5,000 mile) filter change was performed.