Some 2024-2026 Chevrolet 5500 HG/5500 XG Low Cab Forward (LCF) models equipped with the 6.6L V8 engine (RPO L8T) and 6-speed Allison automatic transmission (RPO MW7) may have several DTCs set in the Transmission Control Module (TCM) along with an illuminated Check Engine light. DTC P0711 (Transmission Fluid Temperature Sensor Circuit Performance) and P0700 (Transmission Control Module Requested Malfunction Indicator Lamp Illumination) may set in the TCM due to corrosion of the TCM chassis ground terminals. This condition may be found more often on vehicles driven in cold climate regions where salt is spread on the roads.
If DTC P0711 is set, inspect the TCM chassis ground terminals J-400 and J11, located on the bottom of the right-front frame rail behind the front bumper. (Fig. 18)
Fig. 18
Remove the ground bolt from the frame rail and use a wire brush to clean the bolt, ground terminals and frame contact area. All bare metal surfaces should be completely clean of any corrosion. Install the bolt with both grounds and torque to specification.
In addition, check that the connector cavities are clean and dry. Apply dielectric silicone lubricant to the ground terminals and bolt.
Test drive the vehicle and confirm the DTCs have not returned. If DTC P0711 sets, the vehicle should be referred to a certified Allision repair facility.
For more information, refer to Bulletin #25-NA-354
– Thanks to Rich Renshaw
