Thanks Mark, I am on the "edge" firmware and have the verbose logging already enabled. The tx is being logged ok but no rx back. Another anomaly is it will sometimes go from PoweringOn to PoweredOn with no apparent response to the AT command being sent, then times out back to PoweringOn. So there may be a hardware failure, voltage level shifter perhaps? I will try putting an oscilloscope on both ends of transmission next. In testing I simply modified the simcom 7600 driver code to override the default modem driver so as not to effect the 5360 pulse logic. The spec sheet also mentioned it takes the UART around 11s to respond after power up. Using the spec sheet timing with a delay after turning on appears very reliable on mine in powering up and down the module. Whereas the 2s and 6s pulse turned it on and the 4s pulse turned it off going by the led status.