Allison

Allison 1000 & 2000 Gen 4 Fault Codes: U1301 J1850 (Class 2) Serial Data Communication Link Low

CIRCUIT DESCRIPTION:
Applications that employ J1850 class 2 serial communication use wire 130 to send operational information and commands among the various control modules. Included modules would be Powertrain Control Module (PCM), Antilock Brake System (ABS) Controller, Truck Body Controller (TBC), and Instrument Panel Cluster (IPC). Each controller sends out a state of health (SOH) message approximately once every second. The TCM uses these SOH messages to monitor the condition of the devices on the class 2 serial link.

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 18V and less than 32V (24V TCM).

CONDITIONS FOR SETTING THE DTC:
DTC U0032 is set when high voltage is detected on the class 2 data circuit for more than 3 seconds. This would normally indicate a short-to-power at wire 130.

ACTION TAKEN WHEN THE DTC SETS:
1. The CHECK TRANS light does not illuminate.
2. DTC U0032 is stored in the TCM history.
3. TCM uses default values for missing/erroneous information.
4. 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. The TCM self-clears this DTC when software detects a failure recovery has occurred.

DIAGNOSTIC AIDS:
1. If communication can be established with the Scan Tool at the OBDII connector, then the U0032 should be shown in failure records only. This may indicate that an intermittent short-to-power was present at one time. Refer to Identification of Potential Circuit Problems information.
2. It is not possible to communicate with J1850 with this DTC active.
3. Use the J 43890 T-harness to communicate with the TCM to determine if the U0032 is still active.
4. U0032 in failure records may be present along with a U1000-U1096 that is active. This would indicate that the malfunction occurred when the ignition was ON.
5. This code indicates that voltage is high at wire 130. Normally, this is an indication that a short-to-power exists at wire 130. Inspect wire 130 for this condition.

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 this DTC is active an engine no-start condition may exist. Class 2 messages will not be sent to enable the fuel pump and starter.

Allison 1000 & 2000 Gen 4 Fault Codes: U2104 CAN Bus Reset Counter Overrun

CIRCUIT DESCRIPTION:
J1939 is the protocol currently used in medium duty applications to allow communication between an electronically-controlled engine and the OEM transmission. A signal is sent over a two-wire network harness that incorporates two 120 Ohm resistors in parallel. There are two versions of J1939 currently in use in the medium duty market. Version J1939-11, the most widely used, incorporates a third shield wire. There is also J1939-15, which uses a two-wire connection without shielding.

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. Engine speed is greater than 200 rpm and less than 7500 rpm for 5 seconds.

CONDITIONS FOR SETTING THE DTC:
DTC U0073 is set when the TCM detects no communication on the Controller Area Network (CAN) backbone harness for 3 seconds or more. This may be due to a shorted wire to ground or power in the CAN backbone harness.

ACTION TAKEN WHEN THE DTC SETS:
1. DTC U0073 is stored in the TCM history.
2. The CHECK TRANS light does not illuminate.
3. The TCM defaults to the last-used adaptive shift values and engine throttle percentage is calculated from torque clip speed.
4. 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:
1. If communication can be established at the vehicle nine-pin connector and U0073 is listed in failure records, this indicates an intermittent short condition was present.
2. When diagnosing for intermittent shorts-to-ground, massage the wiring harness while watching the test equipment for a change. Refer to Wire Check information.
3. If an active U0073 is present, Scan Tool communication will not be possible. The cause of the active DTC must be discovered and repaired before communication can be established with the TCM.
4. A short between wires 129 and 132 within the CAN harness can cause this DTC.
5. A short between wires 129 and 131 within the CAN harness can cause this DTC.
6. A short to a vehicle ground and wire 129 can cause this DTC.
7. A short to vehicle power and wire 132 can cause this DTC.

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.

For proper data communications it is necessary to have two 120 Ohm resistors installed in parallel at the J1939 CAN backbone harness.

If this DTC is present in a new vehicle, harsh shifting may occur due to adaptive function inhibit (DNA).

Allison 1000 & 2000 Gen 4 Fault Codes: U2105 CAN Bus ECM Error

CIRCUIT DESCRIPTION:
J1939 is the protocol currently used in medium duty applications to allow communication between an electronically-controlled engine and the OEM transmission. A signal is sent over a two-wire network harness that incorporates two 120 Ohm resistors in parallel. There are two versions of J1939 currently in use in the medium duty market. Version J1939-11, the most widely used, incorporates a third shield wire. There is also J1939-15, which uses a two-wire connection without shielding.

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. Engine speed is greater than 200 rpm and less than 7500 rpm for 5 seconds.

CONDITIONS FOR SETTING THE DTC:
DTC U0100 is set when the TCM detects that no engine torque or throttle messages are being received on the Controller Area Network (CAN) backbone harness for 3 seconds or more.

ACTION TAKEN WHEN THE DTC SETS:
1. The CHECK TRANS light illuminates.
2. DTC U0100 is stored in the TCM history.
3. The TCM defaults to last-used adaptive shift values and engine throttle percentage is calculated from torque converter slip speed.
4. 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:
1. Often an active U0100 will prevent Scan Tool communication with the TCM. Install J1939 T-adapter harness J 43890 to confirm that the TCM is operational. This harness is only useful to confirm that the TCM is able to communicate with the Scan Tool. An active U0100 will be set whenever J 43890 is used.
2. When Scan Tool communication with the TCM can be established at the nine-pin vehicle connector and the U0100 is active, generally it points to an open connection at wires 129 or 132 at the ECM or a terminal in the wrong location at the engine ECM connector.
3. Engine ECM parameters improperly set can cause this DTC to set.
4. A missing terminating resistor can cause this DTC to set. This will prevent Scan Tool communication with the TCM or produce very erratic communication.
5. If DTC U0100 becomes active shortly AFTER an engine update and the troubleshooting procedure for U0100 has been performed.

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 diagnosing for an intermittent open, massage the wiring harness while watching the test equipment for a change. It may be necessary to check for 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.

Intermittent cycling of the TCC could indicate a J1939 wiring problem exists. It is possible to have an open condition at the CAN backbone harness allowing TCC to cycle without a U0100 setting. For a U0100 to set, an open condition needs to be present for 3 seconds.

For proper data communications, it is necessary to have two 120 Ohm resistors installed in parallel at the J 1939 CAN backbone harness.

If this DTC is present in new vehicle, harsh shifting may occur due to adaptive function inhibit (DNA).