Allison 3000 & 4000 Gen 4 Fault Code: P0659 Actuator Supply Voltage 1 (HSD1) High

DIAGNOSTIC RESPONSE:
DNS, SOL OFF (hydraulic default)

CIRCUIT DESCRIPTION:
The high side drivers are connected to the high side circuits of the solenoids and commanded on during normal operation. The high side drivers serve as a master switch to supply battery voltage to the low side drivers. High side drivers are turned on during TCM initialization and remain on during normal operation. High side drivers are turned off during cranking and for certain diagnostic responses. High Side Driver 1 (HSD1) supplies battery voltage to the Main Mod, Pressure Control Solenoid 4 (PCS4) and Pressure Control Solenoid 6 (PCS6) via wire 111. The TCM regulates control current to the solenoids by switching the appropriate low side driver on and off. This test detects if the voltage measured at the HSD1 detection circuit indicates high during initialization when the circuit is off.

CONDITIONS FOR RUNNING THE DTC:
During TCM initialization while high side driver is commanded off.

CONDITIONS FOR SETTING THE DTC:
This DTC sets during TCM initialization, if HSD1 voltage detected to be greater than 6V while the HSD1 circuit is OFF.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P0659 is active:
1. Transmission fails to Neutral (N).
2. DTC is stored in the TCM history.
3. The CHECK TRANS light illuminates.
4. The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool 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 failure.

DIAGNOSTIC AIDS:
DTC P0659 can be caused by:
1. HSD1 circuit issues such as:
– W111 shorted to another wire in chassis harness.
– W111 (terminal 1 of 20-way) shorted to another wire in the internal transmission harness.
2. Two or more low side driver circuit issues with Main Mod, PCS4, or PCS6.
3. Main Mod issues such as:
– W174 shorted to another wire in chassis harness.
– W174 shorted (terminal 8 of 20-way) to another wire in the internal transmission harness.
4. PCS4 issues such as:
– W155 shorted to another wire in chassis harness.
– W155 shorted (terminal 2 of 20-way) to another wire in the internal transmission harness.
5. PCS6 (7-speed only) issues such as:
– W178 shorted to another wire in chassis harness.
– W178 shorted (terminal 7 of 20-way) to another wire in the internal transmission harness.
6. Broken or defective connector assembles allowing pushed back pins to short together.
7. Unlocked connectors, missing seal plugs allowing moisture in connectors.
8. Defective TCM.

Review applicable information in Control System and Transmission Specifications to find additional circuit specifications, system and connector diagrams, and troubleshooting tips.