07 Expy fuse 74 blown, then replaced. Now no crank no start. No ground from pcm.

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BabeWins

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2007 Expedition 5.4 EL Limited. 142K miles Wrench light came on while driving to work with no CEL. When I cranked it to limp home, The CEL and wrench light was illuminated. Codes were consistent with Fuse 74: P0010, P0010, P0102, P0135, P0141, P0155, P0161, P0443. Replaced Fuse but could not find culprit on visual inspection of wires. I traced and doctored all grounds, cleaned the MAS, throttle body, replaced air filter, changed starter (dang top bolt!), and cleared PCM. Drove around neighborhood slowly to relearn and P0020 returned and would not clear. Next morning NO CRANK NO START! Replaced the Crankhaft sensor with no avail. I was able to crank by using my power probe on pin 85 of starter relay. It will run and idle perfectly for about a minute, then idle revs and dies. I’m assuming that the ground supplied by the PCM is my issue, as no ground is supplying pin 85 on Starter relay, Dies once PCM is asked to take over fuel pressure, and New code displayed after dying: U0101 Lost comm with TCM? Any direction on chasing this down? I assume that I’m missing a short to ground, but not sure where to start. Is there any other components outside of those components of “Fuse 74” that would cause no ground from PCM? The PATS system is fine. The only history leading up to this issue was a few intermittent No crank and no starts, but never has stranded me... and the radio the day before quit working, but started working again after I replaced the starter. It has rear air suspension that has been stuck in the up position for years, but can’t relate any of these to the PCM ground.
 

Hamfisted

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Tried disconnecting the battery negative terminal and letting everything reset ?
The P0020 code could be a faulty VCT on the driver's side, or a issue with the wiring harness going to it.

VCT Solenoids at Rock Auto

VCTS-1000-1-ANG__ra_p.jpg


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BabeWins

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Yes have let the PCM reset. I’ve traced the wires and found no issues and replaced the camshaft position sensor on both sides. The PCM is not supplying ground,
What would cause PCM not to supply ground to the starter relay if all conditions are being met for ignition, PATS, neutral safety, gear selector, and cause no crank no start?
Where do I start?
 

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BabeWins

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I have a "listener" ordered to help quickly test for short to ground in all related wires/connectors associated with fuse 74.
 
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BabeWins

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Update. Performed a pin out from PCM to all items associated with fuse 74 (original culprit blown.) When completed, decided to jump from pin 85 from starter relay and noticed that I had a ground for the first time with key in run position. So I inserted the relay and it Cranked! CEL immediately upon crank. Cleared the codes and drove it around the block. Real time data showed P0344, but no CEL until rerank.
3 Codes remain: P0020, P0340, and P0344. I could really use some help! What next? Anyone run into this before? I assume it has something to do with to with a short in the starting system, since no crank no start previously and no ground from PCM to starter relay?
 
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BabeWins

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Upon pin out of pcm with listener, it showed continuity on every pin and tone from pin to all connectors. I thought to myself great. no help. I decided to plug everything back in and see if I had ground back to the starter relay… I did! Expy cranked right up! After brief around the block, P0020 showed back up. I decided to switch the two sensors with one another and code did not follow sensor. Still showing P0020, but idles perfect. when I punch it, just not getting good response.. definitely power loss above 3000, almost like in limp mode but not cutting out. About to take it up to parts store and have alternator output tested and buy some cleaner for PCM/ECM pins and connectors.
Thinking it’s all connector issue at this point? Anyone have similar issues?
 

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