A whole bunch on p-codes lol

[17MagMetal]

Yeah. Far cry from 'no gas' eh ? Hope now you get why I got a little peeved at yer comment.

Hah, agreed. Tone is hard to convey over text, I gotcha.

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[Nick the Crab]

I recently battled fuse 40 with a used 2016 I picked up. My issue was a little different! I'll share it here for anyone else that has this issue.

The car had lth, rxt clutch, 18+ intake, and various other mods. During my initial inspection and test drive I noticed A/F seemed a bit too steady at 14.0. Took it up to speed and engine braked down to 20mph. Gauge showed vacuum, but now lean A/F... That's a problem!

That night I came home and did some research; fuse 40 was a likely source. The next day, I came prepared with my fluke and a box full of 20A minis. Sure enough, the installed fuse 40 was blown. I pulled it and measured resistance to gnd & 12v rail. 750k+ ohms! Popped in a new fuse, cranked it up, and got good* A/F readings. I ended up purchasing the car and started driving home. I got about 10 miles up the road when I noticed A/F was back at 14.0... Measured again - dead short to ground. Great!!

Fast forward a week. I'm stressing about finding this intermittent short. The car is LOW low and I don't have a suitable concrete surface for this kind of jacking.

After reviewing the wiring diagrams, I decide to do what ever I can top side to narrow it down. The easy first step was disconnecting all cam phasers - the short remained. Next, I removed the two connectors from the pcm - the short remained. This was a relief as I did not want to have to open up the pcm and look for failed components... I went ahead and rung out all the pins while these connectors were off. No shorts to ground, so the short must be on the high side of a sensor/actuator. The next area to look is on the back of the intake manifold. I knew it had a ported 18+ manifold, I did NOT know it had IMRC lockouts...

At this point I had a pretty good suspicion that I would find my issue here. There would be 4 connectors behind the manifold that were no longer connected. Did the previous owner or shop fail to secure them? Did they cut them off and leave exposed wires?? Who knows! I climbed on top of the strut brace and started wiggling around harnesses while I had my meter triggered on continuity check between downstream fuse 40 & ground. Sure enough the tone was intermittent while wiggling the harness... After removing the engine cover and climbing in a little deeper, I see the problem! Some how the shop that installed the clutch fully ate a connector with the transmission. Since the connector harness was damaged beyond repair, and the IMRC was locked out, I made the decision the just cut the harness as close to the trans as I could. The hanging wires were then properly isolated and secured.

The short is gone! We have functioning O2 sensors!! Now comes the interesting part... If the seller is to be believed, he had the clutch done 5000 MILES AGO! The car has been running in limp mode the entire time based on dtc duration flag... Also, at some point, the car was remote tuned by palm beach dyno. You'd think they would have said something if they had no A/F data right??

Anyway, hope this wall of text helps someone in the future. I'm happily working through my basket case of a 2016 mustang GT premium convertable

 

[WildHorse]

The short is gone!

good that you found that ! I also have a 2020 intake manifold w/ IMRC lockouts, first thing I did was zip tied it all to the main harness running along the firewall.

 

[WildHorse]

The fuse . as you can see, it didn't pop.

 

[WildHorse]

The fuse . as you can see, it didn't pop.

Can anybody guess why this happened ? I found the answer today.

 

[WildHorse]

No one ? Come on now.

 

[Nick the Crab]

Yes, that's usually caused by high resistance at the contact. It appears you are not getting an effective wipe on the fuse lead. See how the tin plating is scuffed on the non-melted side?

 

[WildHorse]

Yes, that's usually caused by high resistance at the contact. It appears you are not getting an effective wipe on the fuse lead. See how the tin plating is scuffed on the non-melted side?

Give this man a cigar.

Barely contacting.

Took it for a cruise Sunday, all was good then the STFT started wildly fluctuating, long story short. bought the smallest files I could , cleaned them then used dental pics to pull them out a little.

Been right as rain ever since.

 

[WildHorse]

Used this stuff to clean all the contacts . took off a lot of residue. Highly recommended.

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