Allison 1000 & 2000 Gen 5 Fault Code:P0657 Actuator Supply Voltage 1 Open

CIRCUIT DESCRIPTION:
High Side Driver 1 (HSD1) supplies battery voltage to the Main Modulation, Torque Converter Clutch (TCC) and Pressure Control Solenoid 1 (PCS1) solenoids via wire 111. HSD1 is continuously on during normal operation except during brief circuit tests. The TCM regulates control current to the solenoids by switching the appropriate low side driver on and off. DTC P0657 indicates the TCM has detected multiple low side circuits are open while having HSD1 voltage. DTC P0657 could be caused by open condition in the high side wiring attached to HSD1 (wire 111).

ACTION TAKEN WHEN THE DTC SETS:
1. Main modulation is inhibited.
2. If the failure occurs while in a forward range a shift to 1st, 3rd or 5th range is made.
3. While diagnostic response is active, if the shift selector is moved to N (Neutral), the transmission shifts to neutral; if the shift selector is moved to R (Reverse), the transmission shifts to reverse. If the shift selector is moved to D (Drive) range or R (Reverse) and the transmission is compromised by overspeeding or direction change, the transmission shifts to neutral.
4. The CHECK TRANS light illuminates.
5. The TCM forces variable main mod off.
6. The TCM inhibits TCC engagement.
7. DTC is stored in the TCM history.

CONDITIONS FOR CLEARING THE DTC:
The diagnostic tool may be used 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 OEM procedures or in any OEM Troubleshooting or Service information and should not be used as a method to diagnose any transmission DTCs, function, or shift quality concern:

1. 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 Breakout Box, the appropriate harness adapters, and appropriate magnetic overlays to troubleshoot the vehicle.

2. 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 Breakout Box and appropriate harnesses with the diagnostic tool to monitor the circuit performance in question unless otherwise specified in the various troubleshooting information.

3. 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.

4. 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 and run time. This data can be useful in reproducing the failure mode when the DTC was set.

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.

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, such as the parking brake drum, or suspension components.

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