Code 2-1 - please help

[MomentSurf]

Im getting Code 2-1 ('21') on my 91 Suzuki 225 (the code comes up about 30seconds after starting on the muffs). The code is for Throttle Position Sensor/ECM. I tested both according to the manual and they both check out good. What else could be triggering this alarm. The first step is to test the ECM voltage which should be between 4.8v and 5.2v according to the manual - I'm getting 4.0v. But I have an extra ECM and I'm getting 4.0v with that as well...I find it hard to believe that both units are bad. Any other tips to track down this issue?

[MomentSurf]

I switched the ignition module with the extra one, Went through all the grounds, ensuring they were tight. Problem went away.