Allison 1000 & 2000 Gen 4 Fault Codes: P0880 TCM Supply Voltage

Allison 1000 & 2000 Gen 4 Fault Codes: P0880 TCM Supply Voltage

CIRCUIT DESCRIPTION:
DTC P0880 sets if an abnormal power-down sequence has occurred. This condition means the Transmission Control Module (TCM) has lost supply voltage (wire 103) before it has finished saving information from that drive cycle. This process is usually completed in less than 10 seconds.

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. Loss of TCM supply voltage before drive cycle data is saved.

CONDITIONS FOR SETTING THE DTC:
DTC P0880 sets during the next ignition cycle if the TCM loses TCM supply voltage less than 1 O seconds after the ignition voltage has been turned off.

ACTION TAKEN WHEN THE DTC SETS:
1. DTC P0880 is stored in the TCM history.
2. The TCM loses adaptive information for the drive cycle.
3. The TCM reverts to previous adaptive settings.

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 diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.

You may have to drive the vehicle in order to experience a fault.