Died while driving

[mremington]

Had my 03 die while on the interstate after getting the fuel pump and injectors replaced. Was running great and then engine cut off completely. Try to restart and no crank, dash lights up you hear a few clicks under the hood but nothing else. Fuel pump doesnt engage, nothing. Starter was jumped and spun but that's it. Swapped some relays and checked fuses and looks fine. Battery also tested fine. Mechanic thinks its the ECU as my scan tool says it cant connect to the computer now where before it was fine. He tried swapping the ignition switch but no luck same as before thought ive heard of these switches being bad out of the box.

One odd thing was during the pump and injector replacement we noticed the Positive battery cable was corroded pretty bad (falling apart) so the battery was replaced since it sat since around in the garage since end of December. The mechanic had to use a small hose clamp to tighten the cable around the post of the new battery and wasn't until it was snug that the car fired up, until then it was dim lights and no start until it was tight. I ordered a new cable but was wondering if this maybe this fried something?? I'm not sure and at a loss here, sourcing a computer now just in case but I wanted to check with the experts as my guy seems knowledgeable but yall know these cars like nobody else.

Thanks all!
Karl

[Mr. Man]

When you turn the key on (not start) does the FP buzz

[mremington]

Nope not a peep. I didnt hear any relays either this afternoon. Unplugged the battery for a half hour and then Tried my bluetooth obd2 and the SCT scan / programming tool that came with the car to see if either could see the computer and they could not connect to pull any codes. Getting a tow tomorrow so the shop can look at it. Ran like new for about 20 min and shut off doing about 70, never tried to turn over after that only dash lights and some clicks under the hood. Marty suggested checking the wiring as it sat in the garage almost 2 months until the fuel pump was replaced so maybe mice or something chewed into it at some point. At least before when the pump was dead it attempted to crank. Would a bad ECU cause these issues?

[03Merc]

It's the main pcm wire behind the bumper cover in the loom that wraps around the rebar....most likely.


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[03Merc]

https://uploads.tapatalk-cdn.com/20250224/4a09257afd28becc752901a1456eb6 10.jpg
https://uploads.tapatalk-cdn.com/20250224/a567059f4bbd92a7865cadb45445a5 5f.jpg


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[03Merc]

https://youtu.be/TZ--BMz2X_k?si=0EHd2AiDS6xrg2O0


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[mustangeddie]

Sounds like you have a couple of issues. First thing I would do is fix the battery cable properly there are so many electronics in the car that rely on that having a good connection. Second if you don't hear the fuel pump running and confirm it has no fuel pressure I would suspect a defective fuel pump. What was the reason for changing the pump in the first place. If it turns out the ECU is bad I have a good one from an 03 if you need it.

[mremington]

We'll check wiring tomorrow where you've indicated, along with replacing the battery cable harness that arrived today. Replaced the pump because right before Christmas I drove it down the road came back home and it wouldnt start after that, no noise from the pump but it would at least try to turn over, had some codes for 2 or 3 bad injectors as well. After pump and injectors replaced it started up codes cleared and halfway into driving I noticed the check engine light pop back on but it was still running great until it just shut off. Hoping its not the ECU obviously but trying to track one down just in case since I cant even talk to the thing. I'll show all this to him too so he can check what yall are suspecting. Really appreciate the help guys! And I'll grab that 03 ECU from you for sure if its bad. Figured I'd get a tune from Marty while I was at it, this one has an old Reinhart tune I think from when it was purchased.

[Mr. Man]

Fixing the battery cable is a good thing regardless of the other issue. I'd put the car up and give the connection points for the fuel pump a good going over. Perhaps a connection came loose.

[mremington]

Dropped it off yesterday and showed him the pictures and posts here as a reference, waiting on an update later today or tomorrow. He's pretty methodical but I'm hoping the info here can be of assistance especially the wiring issues around that area. I would think if the ECU fried it wouldnt run great at all like it was for about 20 min but the loss of comms is concerning me. Thanks again!

[03Merc]

Dropped it off yesterday and showed him the pictures and posts here as a reference, waiting on an update later today or tomorrow. He's pretty methodical but I'm hoping the info here can be of assistance especially the wiring issues around that area. I would think if the ECU fried it wouldnt run great at all like it was for about 20 min but the loss of comms is concerning me. Thanks again!

No communication to pcm from the Obd 2 port is for sure that yellow wire.


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[mremington]

Nothing yet unfortunately. He did some checking today, gets a signal from the ignition switch, starter is good and said tomorrow he would be able to put it up on a lift and start in on it full time. I again mentioned the wire harness and the spot to check along with the yellow wire and he has not been able to check it yet. He did say he would swap in a stock (I assume crown vic or gm) ECU and see if it could be read by a scan tool. I'm assuming that would at least verify if the current one is bad or if no comms that the wiring is obviously faulty somewhere.

I did tell him to check the link to this thread as well for pictures and your input. I'm hoping tomorrow I'll have some solid answers and can move forward accordingly. Thanks again everyone, your feedback is much appreciated.

[mremington]

So before he moved to put it on a lift it tried to crank, fuel pump came on, engine tried to start. Next key turn nothing again. Swapped pcm for a crownvic/marquis and could read it with a tool, swapped old one back and no comms. Then swapped the crownvic/marquis one back again and no comms. Pretty much has to be a wiring issue at this point so I asked specifically for him to check the wiring you mentioned and the area behind the driver side wheel well. I'm just waiting on the results now.

[crouse]

Do you have take the bumper cover off?

[mremington]

Actually just spoke with my guy this morning. Turns out a lot of the wiring was bad, same as the video and pictures above. Some spots were corroded like the battery terminal and another looked like a mouse or something chewed it so with all that I grabbed a chassis harness from an 03 to be safe. Assumption now is it was just bad timing (or good depending on how you look at it) that this cropped up after the fuel pump / injector swap. I'd rather run off a known good harness than risk the engine cutting off doing 90 again, it was not a fun experience. Hopefully I'll have her back this weekend, been driving the wifes car lately and the fuzzy pink steering wheel is getting old.

Any other tips or concerns I should know about given this problem? Anything you guys would look over or have done while this is getting fixed? Just curious again what the experts say. Thanks Gents!