Hi. I'm new to the forum. (Well, My first post anyway) I have a 96 3.9. 90,000 original miles. Bought it new. It just won't start. Read up about code 42. I switched out the two relay's/fuses in the box on the firewall. Still nothing. Timing chain was replaced about 5000 miles ago. Sprayed ether in the TB. No pop at all. Did the three wire (red/wht) to one check and reconnect. Since I've disconnected the battery all I get now is a 55 code. Before had a 21 and 42. If it was a fuel problem I would get at least a pop when turning it over. Yes? The splice was in real good shape. No corrosion at all. It was sealed real well and had shrink wrap around it, but as long as I was there I went ahead and cut it all back and redid it. Since the original code was the 42 I would assume it is has something to do with the ASD relay or orange 30 amp ASD fuse. Switched them out with the ac relay and another 30 amp fuse in the box. I read it may be the ECM. Is that a possibility and if so how can I check it? Where is it? Any help would be appreciated. The day it did it it was a sloppy wet snow on the road. Drove home parked it and when I went to start it. Nada. Thanks in advance. Bob

 

I'm having the same problem myself and was just about to post it. I have a 91 with a 3.9L and manual trans. It's been running great until last night when I went to start it. Its not turning over at all. checked the codes and it gave me #42. I've switched fuses and relays with no result.
Any sugestions would be great

 

Sounds like it is a wire problem. The codes are.
21 02s sensor problem (oxygen sensor), upstream or down stream
42 Fuel pump relay control ckt, Auto shutdown relay control ckt, No ASD relay output voltage at PCM, Fuel level sending unit volts out of range, Fuel level unit No change over miles
So a code 42 to me sounds like the computer is not receiving power to give that power to the relays. So check at the computer terminals for power at the power inputs. If need be we have the wiring diagrams in the service manuals in the FAQ in this section. The computer is located on the passengers side fender.

 

would that be the problem if its not cranking or could it be something else

 

It could be anything. It could be totally unrelated to the code.

 

Hi. When I try to search the FAQ section it comes back with no matches on thing like "1996 3.9" or "code 42". Just keeps showing me to a calender of events, etc. What am I doing wrong? Any help appreciated. Bob

 

You need to look in this section. Look at where you clicked on this post. Now just look above that post. Look to the left and you will see a green arrow pointing at it.

 

I got the truck fired up !!. Put everything back together, went to the computer on the left fender and wiggled the wires around. I had a mechanic coming today to see if we had spark etc. Just wanted to put the box on the drivers side back on where I took apart the three wires. I didn't have any solder so I used a wire nut and electrical tape to reconnect them. I don't think that was the problem. My truck was made in late Oct. of 96 and they may have dealt with this and tried to correct it because it was not corroded at all. Had the resin and shrink wrap and was still a new copper color. I left the battery off all night. I don't know if messing with the wires to the computer did it. When it warms up. I will clean up the contacts up on the ECU. I went and put some more gas in the truck with some water dryer. It was 7 deg. this morning, so I figured might as well cover that base too. I still don't feel confident with this until I find out what caused it. No check engine light so far. I'm sure the 21 code will come back. That started when the dealership had to put a new Cat on it and O2 sensor. But as usual, that can't be anything they did. So thanks for the info. and now that I'm a member, I'm sure I will be back.

 

Glad to hear you got the truck running and sorry for the thread-jack. I think I've traced my issues to the starter and should be back on the road soon too.

thanks for everyone's help