troubelshooting code 46

[fgross2006]

I have this code for a few weeks that I know of. Seems to be the only code present in KOER.

Today I swapped out my ratty patched up negative battery cable for a repro correct one with the extra ground and the ECM ground connector. So as along as I had the hood up and it was a nice day here on Long Island I decided to take a shot at troubleshooting the code 46 I have.

Since code 46 says no Thermactor bypass I checked the situation on the TAB. The first this I did was to pull the vacuum hose and placed my vacuum pump onto the nipple of the TAB and applied vacuum manually. Then i ran the KOER scan and low and behold no code 46. But now I have codes 21 and 41. Hmmm.

I heard the engine kind of click when the ECM applied vacuum to the TAB. Since I had that hose off the TAB I heard it suck vacuum. I applied my vacuum gauge and it said 20. I then noticed the hose that goes to the TAB was flared they way rubber hose gets when it has been sitting in the same position a long time. apparently the original cream colored hard vacuum line is still there but the original connector is gone so a 4 inch piece of vacuum tube was slid onto it. I replaced the old vacuum tube with a new piece 1 size smaller so I could insure a snug fit.

Since i verified the ECM was switching the solenoid on and vacuum was being applied to the TAB line, and since I verified no code 46 when I had manually applied vacuum I was sure the hose was leaking at the flare. No so. After connecting the tighter hose to the TAB, while the ECM was still pulling vacuum on that line, I still picked up code 46 doing another KOER but 21 and 41 went away.

So I assume that when the TAB vacuum line was disconnected it was drawing air which explains the codes 41 and 21 showing up only when that line was not connected. But how is it possible that I still get code 46 when I felt vacuum pulling on that line and measured it with a vacuum gauge just before I reconnected it to the TAB? Especially since I verified there no code 46 when I apply vacuum manually?

I have a spare, used TAD I can swap just to troubleshoot further, The one that's on the car was a NOS Motorcraft I installed around 4 years ago.

Anybody have insight on this?