Allison 1000 & 2000 Gen 4 Fault Codes: P0701 Transmission Control System Performance

Allison 1000 & 2000 Gen 4 Fault Codes: P0701 Transmission Control System Performance

CIRCUIT DESCRIPTION:
The Transmission Control Module (TCM) monitors the status of the pressure switches at start-up to detect the presence of hydraulic pressure.

CONDITIONS FOR RUNNING THE DTC:
1. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM).
2. Engine speed is greater than 200 rpm and less than 7500 rpm for 5 seconds.
3. This test is run after engine start-up and runs as part of the transmission hydraulic initialization.

CONDITIONS FOR SETTING THE DTC:
DTC P0701 sets when transmission fluid temperature is above -25°C (-13°F) with an engine speed above 500 rpm for 6 seconds or 400 rpm for 15 seconds and forward or reverse range is selected and all the pressure switches do not indicate pressure.

ACTION TAKEN WHEN THE DTC
1. DTC P0701 is stored in the TCM history.
2. The TCM inhibits TCC engagement.

CONDITIONS FOR CLEARING THE MIL/DTC
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 failure.

DIAGNOSTIC AIDS:
1. DTC P0701 may be logged if a forward or reverse range is selected immediately after the engine is started and before the TCM detects pressure at the switches (2 to 6 seconds after engine start).
2. A plugged control main filter may cause this code to set. The control main filter is to be changed after the first 8000 km (5,000 miles). Failure to change the filter at this interval may cause this code and other pressure switch codes to set.
3. A cracked internal suction filter tube or damaged tube seal may cause this DTC to set.
4. A stuck lube regulator valve (located in the front support) may cause this DTC to set. A high static oil level with the vehicle running is often a good indication of this complaint. Often pressure switch DTCs are set in this scenario.
5. You may have to drive the vehicle in order to experience a fault.