hey all I have a 1995 bronco 5.0
i was having a no start issue I was getting spark and fuel I was not getting injector pulse. I changed the computer thinking that was the issue. Now I have an intermittent start issue where it starts then it has to cool down to start again. It willl stall when I put it into gear it immediately stalls. So I scanned it I got codes 629,121,542, and 543. Now I am totally lost and don’t know where to look next any help I would appreciate thanks.

 

600-series Codes are all related to the E4OD transmission. 629 is a torque converter circuit failure. (Worry about this one if it drives erratically AFTER you get it running right).

Code 121 is indicative of the readings from the TP sensor being "out of expected range" which typically means the varistor has failed or is failing (has "dead spots").

Codes 542 & 543 are related to the fuel pump circuit. 542 indicates a lost ground or an "always on" condition in the pump circuit. 543 indicates a loss of power. The fact that both are present would make me wonder if you have a weak/intermittent power connection in the fuel pump circuit.

Just an FYI, total ECM failure is the problem about .001% of the time.

 

How should I go about checking the fuel circuit.. the pump seems to be working fine mechanically I am getting 40+ pounds at the rail

 

I have found these two websites very helpful:

easyautodiagnostics.com

troubleshootmyvehicle.com