will 177.840(a) put my truck out of service
Maybe. Across our inspection records, 37.8% of 177.840(a) citations resulted in out-of-service placement. That's higher than the all-FMCSR average of 31.4%, but this violation is not automatically OOS-eligible under the regulations. The inspector's assessment of hazmat documentation severity determines placement. If cited, ask the roadside inspector whether your specific violation triggered an out-of-service order.