6 cylinder misfire no/low energy Pulse at injector for 6cyl. What can be the problem? Ground wire, ECU?

Scan for codes other than misfire, check fuel pressure and check for a vacuum leak.

Do what has been suggested first

Check for bent pins at ecm or looseconnections. Also check for bad connections at aldl. It may be a bad ecm but check to see if #6 is even getting a signal. Normally you need a noid light for that though. What is fuel pressure? Is it within specs?

What was the original code that was set? If it was 16 then that is a faulty ecm. Course you said you coudlnt' pull it out.
Try this test although you dont' need to see if theya re working or not. Check resistancein #6
1. Start engine. Using a stethoscope,  ensure each injector is making a "clicking" noise during operation. If "clicking" noise is not heard,  ensure wiring connector is securely fastened.
2. Ensure an injector signal is present on injector harness connector. Turn engine off. Disconnect injector electrical connector. Using a DVOM,  measure resistance across injector terminals.
3. Resistance should be approximately 13.8 ohms. If resistance is not as specified,  replace fuel injector. Disconnect negative battery cable. Remove injector from engine.
4. Place injector into a container to catch fuel spray. Turn ignition on. DO NOT start engine. Using a jumper wire,  connect terminals FP and +B of check connector. See Fig. 13.

Fig. 13: Check Connector Terminal ID (ES300 Shown? Others Similar)
Courtesy of TOYOTA MOTOR SALES,  U.S.A,  INC.

5. Connect battery voltage to injector terminals for 15 seconds. Ensure an even,  cone shaped fuel spray is observed from injector. If fuel spray is not satisfactory,  replace injector. If fuel spray is satisfactory,  check
volume of fuel delivered by fuel injector.
6. On GS300,  fuel volume should be 2.4 3.0 ozs. (70 78 cc) for 15 seconds of operation. On ES300,  fuel volume should be 1.8 2.16 ozs. (54 64 cc) for 15 seconds of operation. On LS400 and SC400,  fuel
volume should be 1.9 2.4 ozs. (55 70 cc) for 15 seconds of operation. On SC300,  fuel volume should be 2.4 3.0 ozs. (70 88 cc) for 15 seconds of operation. Check each injector 2 3 times for volume.
Maximum volume difference between injectors isÂ.16 ozs. (5 cc) for GS300 and ES300, Â.17 ozs. (10 cc) for SC400 and LS400,  andÂ.27 ozs. (9 cc) for SC300. If volume is not satisfactory,  replace injector.
7. Remove battery voltage from injector. With injector still placed in container,  observe injector tip. If injector drips more than one drop of fuel within one minute,  replace fuel injector.
Other than that you may have a bad ecu guess it would only be to try one and see if it does same thing. Also have you check main efi relay and fi fuse? And clean ground on back of right rear cylinder head that is the main ground for fuel injectors, ecu etc.

Also there may be a break in the ground wire for injector#6