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Hey guys,2003 Ford Excursion 6.0L Powerstroke (not the original owner). Been chasing codes and electrical gremlins using FORScan. Trying to stay methodical and not just throw parts at it.Current issue / codes:Persistent P0720 / P1832 / P1876 (Output Shaft Speed Sensor circuit) – OD flashing.Confirmed:PCM is completely stock: VXAP2A2TCU: TQAU0N4No prior PCM or TCU swaps or reflashes. Symptoms only happen when the truck is warmed up, and persist until it cools down, then it starts all over when wam again. OD flashes and goes into limp mode stuck in 1:1 gear 5.What I’ve done so far:Full FORScan diagnostics and monitoring.Replaced OSS sensor twice: First with a Standard brand unit (code came right back), then switched to genuine Motorcraft DY1250. Still getting P0720.Previouse owner upgraded passager battery charging cable to 2/0 AWG with 250A MEGA fuse.Replaced the alternator after the shop said it had 350mv-500mv ripple. No dice.checked all grounds and battery connection, put in new in passager battery ground cable to tub as that was a little suss. Had a shop ohm OSS wires and they said it was good.cleaned the PCM connections with electrical spay/cleaner.SCT X4 tuner – loaded Gearhead Customs tunes (8K TOW, SRL, and UNLIMITED TOW). Switched everything back to completely stock tune to rule out any tune-related variables during diag.Battery's are both new last year. But I have a battery tester coming in the mail to test those.The 250amp mega fuse blew a couple months ago and replaced that.One thing I do see on Forscan is the OSS registers speed that coralates with RPM and speed, but the 'Actual Output Speed' drops intermittently.Im at my wits end with this problem! Im planning on taking it to a transmission shop to put in jumper wires from OSS to PCM, if that doesnt work the only other thing I wont have done is put a new PCM. The problems gotten more and more consistent as the weathers warned up.Appreciate any experience from you 6.0 guys who’ve actually fixed this ****. Happy to post more live data, parameter logs, or pics if it helps point me in the right direction.Thanks in advance!
This is active limp mode PIDs
The ISS/TSS and OSS sensors are externally mounted on the top of the transmission.
Output Shaft Speed Sensor Circuit (bad connector, bad wiring, OR it could be the alternator producing excessive A/C ripple, or even bad batteries, last possibility IMO would be a bad sensor). Could also be a bad ground somewhere. Ultimately it could be a bad PCM. NOTE - a 12V reference circuit is used for power.
Resistance across the sensor should range from 780 - 1900 ohms,
Note - The sensors VREF and SIGRTN circuits are shared with the internal harness, so IF shift solenoid or TR sensor codes are absent, I would tend to think the problem is not in the internal wiring harness.
P1832:
Transfer case Differential lockup solenoid circuit failed: First inspect fuse 27.
P1832 - Transfer Case Differential Lock-up Solenoid Circuit Failure -----------------
Strangely enough, this code could be a result of doing the mod to eliminate the door chime alarm. Pinpoint Test I
P1876:
Transfer case 2-wheel drive codes solenoid circuit failed: First inspect fuse 27.
Pulse Vacuum Hublock (PVH) Solenoid or Wiring -------------- (disconnected it to do the solenoids test)
Strangely enough, this code could be a result of doing the mod to eliminate the door chime alarm. Pinpoint Test I
The ISS/TSS and OSS sensors are externally mounted on the top of the transmission.
Output Shaft Speed Sensor Circuit (bad connector, bad wiring, OR it could be the alternator producing excessive A/C ripple, or even bad batteries, last possibility IMO would be a bad sensor). Could also be a bad ground somewhere. Ultimately it could be a bad PCM. NOTE - a 12V reference circuit is used for power.
Resistance across the sensor should range from 780 - 1900 ohms,
Note - The sensors VREF and SIGRTN circuits are shared with the internal harness, so IF shift solenoid or TR sensor codes are absent, I would tend to think the problem is not in the internal wiring harness.
P1832:
Transfer case Differential lockup solenoid circuit failed: First inspect fuse 27.
P1832 - Transfer Case Differential Lock-up Solenoid Circuit Failure -----------------
Strangely enough, this code could be a result of doing the mod to eliminate the door chime alarm. Pinpoint Test I
P1876:
Transfer case 2-wheel drive codes solenoid circuit failed: First inspect fuse 27.
Pulse Vacuum Hublock (PVH) Solenoid or Wiring -------------- (disconnected it to do the solenoids test)
Strangely enough, this code could be a result of doing the mod to eliminate the door chime alarm. Pinpoint Test I
So I replaced the passenger battery ground to body. Body ground to PCM reads perfect. That ground wasnt causing the issue, but it looked less than idea so I replaced it with a 4ga wire I had laying around. Batteries tested all good with the Kingbolen BM580. I also replaced the alternator with a new Leece Nievile 240amp alternator (same that was on it before). The BM580 was measuring 10-40mv ripple. I think Ive ruled everything out but a bad PCM at this, assuming the first shop I took it to tested the harness correctly. Anything else I should look at before taking to the transmission shop?
Im going to have them test the harness themselves again to confirm the first diag.
That said, it sounds like you are doing what you can. Sorry I can't help more - this certainly isn't really "my cup of tea".
Sometimes it is the PCM, and my approach has pretty much been "rule out all else", then it is the PCM.
That said, it sounds like you are doing what you can. Sorry I can't help more - this certainly isn't really "my cup of tea".
Sometimes it is the PCM, and my approach has pretty much been "rule out all else", then it is the PCM.
Same. PCM is usually the last thing I suspect when diagnosing.
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