This is what the book says :


Code 4-4-3 (TWC Efficiency... "Three Way Converter")
1) Check for other codes. If any code for misfiring is stored
(Codes 4-5-1, 4-5-2, 4-5-3, 4-5-4, 4-5-5, 5-4-2, 5-4-3, 5-5-1, 5-5-2,
5-5-3, 5-5-4, 5-5-5, 5-4-4 or 5-4-5) perform that testing first.
If Codes 4-3-5 or 4-3-6 are stored, perform testing for that code first.
If none of the above codes are stored, go to next step.

2) Perform a compression check on all cylinders. Repair as
necessary. If compression is okay, go to next step.

3) Check for air leakage in intake system. Repair as
necessary. If there is no air leakage in intake system, check for air
leakage in exhaust system. Repair as necessary. If there is no air
leakage in exhaust system, check fuel and residual pressure. Repair as
necessary. If fuel and residual pressure are okay, retest using NEW Cat Converter.


Mike