obd2 wont read computer

the van has rough idle and engine light is on but multiple obd2 tools have been used and cannot retrieve codes.all fuses are good and yes the cigarette lighter works.any ideas would be great

I would still replace the #17 fuse and see what happens.

What year model are you working on?

replaced the fuse for no reason obviously! and its a 1999 ford windstar

I suggest you do a pin-to-pin ohmmeter check on the harness feeding the data port. To avoid zapping the meter, lift a battery cable during checks.

terminals #4 and #5 are (separate) ground circuits. Black.

terminal #13 (VT) goes all the way to the PCM plug ... pin #13

terminal #2 (TN/OG) ditto ...pin #16

terminal #10 (PK/LB) ditto ... pin #15

.... there is one more conductor, but I don't think its a problem. Good luck!

all wires tested good and grounds too. however i did realize my ignition switch doesnt turn off.the switch test good in the on positions but no way to test the off.ill try a new switch.is it possible that this is my problem?and thanks for offering better advise than changing a good fuse.

I don't know if the ignition switch could be the problem... but I believe in fixing what needs to be fixed ... it might surprise us.

If you haven't already found the actual switch yet, its a black box down inside the steering column covers ... actuated by a long rod that starts out at the key tumbler. A good chance to do some lubrication.

yes i ve had the swith out for testing thought maybe its not turning something since it doesnt turn off. i actually stumbled upon this when i noticed a hot to the touch rely in the fuse box when the key hadnt been on for 2 days. i plan to change the switch asap.when testing the circuit a1 to b1 had less resistance than all others. thanks again and ill let you know the out come of the ignition switch change.

the ignition switch was causing the van to run rough and preventing the obd codes from being read.runs great again . pulled old switch apart and the inside was melted!dont know why it got so hot but it caused alot of problems.ty for your help

Glad you found the problem .... thanks for the feed-back.