Some 2019-2023 Silverado 4500HD/5500HD/6500HD trucks may have an intermittent condition where the available Power Take-Off (PTO) is inoperative along with DTC P251A (PTO Enable Switch Circuit) set in the PTO Control Module.
The PTO is an upfitter integrated auxiliary power source. The PTO system controls engine speed to values higher than normal base idle, PTO load relay engagement, and remote starting and shutdown of the engine.
The intermittent PTO operation may be due to a vehicle ground issue. Before replacing the PTO switch, check and clean the vehicle grounds.
G120 (Main PTO ground on the left side of the engine) – Inspect ground bolt length and the ground eyelet for proper clamp load. Check for red anti-corrosion paint between the block and eyelet. (Fig. 18)
Fig. 18
G340 (Main battery ground on the driver-side frame rail) – Inspect for debris between the eyelet and ground cable.
G398 and G399 (Left frame rail to right frame rail ground cable) – Check for proper tension and eyelet clamp load.
G108 and G110 (Main engine to frame ground on the right front inner frame rail, G108, and on the right side of the engine, G110) – Verify bolt length does not bottom out and inspect red anti-corrosion paint between the eyelet and engine block. (Fig. 19)
Fig. 19
G198 and G199 (Main body-to-left frame rail ground) – Look for proper eyelet clamp load and red anti-corrosion paint between the bolt head and eyelet and the engine block or body stud. (Fig. 20)
Fig. 20
Refer to #PIP6108 for more details.
– Thanks to Bill Alley
