Subject: Allison LCT1000 DTC P1711, P0872 After Completing Repairs
Model: 01-05 Chevrolet Silverado and 01-05 GMC Sierra
The following diagnosis might be helpful if the vehicle exhibits the described symptoms in the PI.
Condition/Concern:
Code P0872 or P1711 setting soon after a transmission repair. Generally, the vehicle did not exhibit the code prior to the transmission repair.
Recommendation/Instructions:
Investigation into DTC P1711/P0872 has shown that in most cases trucks that set this code have had a cracked transmission adapter housing. Bulletin 03-07-30-031 contains details on the adapter housing repair. Cracks in the adapter housing can allow dirt and sand to enter the transmission resulting in stuck shift valves in the valve body. To reduce the possibility of setting a DTC P1711/P0872 when repairing a cracked adapter housing, the following five steps should taken:
Clean the transmission oil pan thoroughly inside and out.
Replace the fluid filter located inside the oil pan (P/N 29537965).
Replace the spin-on fluid filter (P/N 29539579).
Thoroughly flush the transmission cooler and lines using TransFlow tool J 45096.
Be sure that the transmission fluid is refilled to put the oil level in the "cold" range with the engine running and the transmission in park. Do not shift from park into a forward or reverse range until the oil is in this "cold" range.
By reducing the amount of dirt and sand inside the transmission, the chances of setting this DTC will be greatly reduced. The following checks help in determining the if shift valve "E" is stuck in the bore or shift valve "C" has a oversize bore or if the condition is related to the wiring.
Cycle the ignition key to the run position with the engine off, the TFP (Transmission Fluid Pressure) switches "C" "D" and "E" should all read OFF on the Tech II scan tool. Upon starting the engine the TFP switches "C" "D" and "E"should change from OFF to ON The above 2 steps indicate that the TFP switch, wiring and TCM are functioning properly Once the transmission reaches a Steady State first (1st) gear the TFP switches should read"C" OFF "D" ON "E" OFF, if "E" does NOT change to OFF once the transmission has reached a steady state first (1st) gear the "E" shift valve may be stuck in the bore or the "C" shift valve is loose in the bore causing a bleed action to the "E" valve. This will force the "E" valve into the ON position once this occurs DTC P1711 or P0872 will set after 2 seconds. The valve body assembly should be checked for a stuck valve and rear cover should be replaced (if cracked) as required for this condition. The valve body should be torqued to 100 inch pounds. Over torquing the Transmission Fluid Pressure Switch (TFP) may result in shorting out the TFP and setting DTC P1711 or P0872.
If the "E" switch changes to OFF, the condition may be intermittent and the DTC flow chart should be followed to see if another condition can be found for the DTC P1711 or P0872.
