Allison 1000 & 2000 Gen 5 Fault Code:P0218 Transmission Fluid Over Temperature

CIRCUIT DESCRIPTION:
DTC P0218 indicates a sump temperature threshold has been exceeded, this can allow converter out temperatures to reach much higher than acceptable. Torque converter stator One Way Clutch (OWC) function should be tested after achieving high converter out temperatures.

If the TCM detects a high Transmission Fluid Temperature (TFT) for an extended period of time, then DTC P0218 sets.

ACTION TAKEN WHEN THE DTC SETS:
1. The CHECK TRANS light is not illuminated (non-OBD II strategy).
2. The TCM forces Variable Modulated Main off.
3. The TCM freezes shift adapts (DNA).
4. The TCM records the operating conditions when the conditions for setting the DTC are met. The TCM stores this information as Failure Records.
5. DTC P0218 is stored in the TCM history.
6. The shift schedule is altered to increase upshift and downshift speeds, allowing maximum engine rpm for increased cooler flow. Torque Converter Clutch (TCC) remains applied.

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 warmup cycles without failure.

The TCM cancels the DTC default actions when the fault no longer exists, and the DTC passes the test.

DIAGNOSTIC AIDS:
1. Verify cooling system is operating properly. Follow transmission overheat troubleshooting information for problem OVERHEATING IN ALL RANGES.
2. Verify the customer’s driving habits, such as stall events, overloaded vehicle, etc.
3. Using the diagnostic tool, monitor TFT. TFT should rise steadily during warm-up cycles and then stabilize.
4. DTC P0218 may set after DTC P0711 (not active) has set. Follow the diagnostic information for DTC P0711 before proceeding to the diagnostics for DTC P0218. Repairing the condition that set DTC P0711 will likely eliminate DTC P0218.
5. DTC P0218 sets first, before DTC P0711 and DTC P0712.
6. If DTC P0711 is active, temperature is defaulted and diagnostics are shut off, DTC P0218 cannot be set.