Allison 1000 & 2000 Gen 5 Fault Code:P0706 Transmission Range Sensor Circuit – Performance

CIRCUIT DESCRIPTION:
An Internal Mode Switch (IMS) is used by the TCM to detect the angular position of the shift selector shaft. There are five internal switches in the IMS: A, B, C, P, and NS. The TCM uses four of these switch inputs to determine the proper gear range that is selected. The fifth switch (NS), located in the IMS, is used as confirmation that the transmission is in neutral before the engine starter is engaged. DTC P0706 sets when the Engine Control Module (ECM) allows a start in reverse or forward range.

ACTION TAKEN WHEN THE DTC SETS:
1. The CHECK TRANS light illuminates (non-OBD II strategy).
2. The diagnostic response is to shut all solenoids off, allowing the transmission to fail to hydraulic default “limp home”. Shift selector and hydraulic state of logic valves determines range.
3. DTC P0706 is stored in the TCM history.
4. The TCM inhibits Torque Converter Clutch (TCC) engagement.
5. Due to this failure and associated response, DTC P0722 can also set.
6. A shift to R (Reverse) will allow reverse range if DTC P0878 is not active.
7. The TCM forces Variable Modulated Main off.

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 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.

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.