Why I can't read imx7d idcode through jtag port with IEEE1149 tools?

[DaveSim]

I help my firend to trouble-shoot his imx7d manufacture thing. There are some boards can't run after programing .  And because of no test point inside ,so I try to use ieee1149 tools to boundary-scan the pins around imx7d .But I found I even can't read out imx7d idcode through 1149 tool.
My question is what's probably wrong in it ? Or what's diffrent between imx7d-series and other ics? (New ic without programing . It avoid system jtag security things.)  Thanks!

[DaveSim]

Okey,Jtag chain worded . I asked and checked the jtag port part schemtic from my friend after many times Jtag connect fail. I found jtag mode be connected to gnd. Acording to reference manual , the jtag would word as tap mode while the pin be connect to 3.3v.