Complex transmission issues

[Duper Suty]

TL;DR This particular post is asking the question "Did I accidentally clear the codes trying to link the obd-2 while the truck was running"
Reason I'm asking is this may point me in a positive direction for further diagnosis.

To frame the whole situation, I have a 02/97 super duty 2wd E4OD I've gone through the gauntlet of electrical and mechanical troubleshooting for sudden loss of 2nd and drive. Downloaded Forscan and got an elm327 OBD-II through the mail to read codes in an effort to see if any were stored (no CEL or flashing OD light). I have a list of what I've done to troubleshoot I'm organizing into chronological order I will provide once I neaten it up.

Anyway, I made the rookie mistake of running the truck while it was connecting to the obd-2 port. It shut down once it linked and the dash lights went nuts. I closed the Bluetooth link, shut key off, and removed the obd-2 adapter. Truck did restart on its own and cycled the gauges and dash lights fine. I wanted to see if the rest of it was okay afterwards, so I drove it around the block and Drive came back. It drove like it was factory fresh for about 1.3 miles, where I really hammered it going uphill and the exact issues I was chasing returned. Limped it back home, shut it down but put key on and pulled codes with Forscan.

Still chasing issues, but I'm curious if I accidentally did something along the lines of clearing the codes when I linked the obd-2 and it shut down. Codes I pulled after I got it back home are provided in a posted screenshot just for relevancy

Again, I have notes on what I've done in an effort to resolve this that I will compose into its own post.

 

[Duper Suty]

02/1997 F-Super Duty, E4OD 2wd

I've been compiling my notes as stated in that thread and noticed something that I wanted to double check regarding the VSS, so I verified every step to ensure my notes were accurate and they supported my most recent findings.

Sensor itself resisted to 1104 ohms.

Both wires (red/pink-green/black) between the VSS and what I believe is called the C205 connector at the firewall were bad, absolutely no continuity or short to ground. Reran those wires one at a time to ensure color match and verified continuity and confirmed still no short to ground, both via back probe and narrow needle probe of the male/female faces.

Verified no shorting to each other at sensor and connector, both via back probe and narrow needle probe of male/female faces.

Reconnected C205 and performed same continuity and short to ground checks on cab interior side of C205 to the VSS sensor. Observed short while probing inside cab side.

Disconnected C205 again. Probed engine bay face, no short. Probed firewall contacts, short observed.

Took gauge cluster out and verified continuity and short to ground on the wires between C205 and the PSOM connector. Continuity error still observed.

The VSS wires were shorting to each other at the PSOM connector. Depinned the connector, replaced the female contacts, blew out the connector and repinned. After lots of aggressive shaking the wires remained isolated from each other. Unsure what exactly was causing the issue except maybe the little locking ears on the contacts were somehow touching, they did look rough. This time passed continuity test, passed short to ground test.

With VSS connected, getting 1116 ohms at the PSOM connector (in case it wasn't clear before, one needle probe on pink/red wire and second probe on green/black wire at PSOM plug female face and back probe).

This was all done with batteries connected in the truck and key on, used a lead on negative battery post to multimeter probe for solid ground when verifying short to ground.

No codes through FORScan now. Batteries were low so disconnected for the night and put them on the tender. They are reaching end of service life.

Next day, reconnected batteries and tried to move truck. Reverse is strong, like stab throttle and chirp the duals strong, but all forward gears still just feel the limp engagement but engine throttle doesn't move truck forward

At this time confident in the integrity of the VSS circuit I wanted to verify calibration on the PSOM after reconnecting the PSOM itself. Held reset on cluster, turned key on, got E 08 6, select button then 969CAL showed. 235/85r16 tires with 120 tone teeth and 4.63 ratio math'd out to 954, so cycled it down to 954CAL and saved the change. To verify it took, cycled key off, held reset, key on and E 08 5 showed, meaning it took the change. (Speedo needle swept fully both times)

Put rear axle on jackstands to attempt a running/rolling test of the VSS function. With O'scope back probed at the sensor connector, truck running in first gear foot on brake, no graph movement on scope, minor fluctuations on readout that matched the scopes idle readout if the probes weren't connected to anything.

Let off brake, wheels spin, 0.71-0.77VAC at engine idle. Speedo needle ~4mph, graph is extremely erratic with no form.

Get it up to 10mph on speedo, 1.68-1.73VAC, graph still erratic. Shut truck off.

Back probe PSOM connector with scope while still plugged into PSOM, start truck again, 1st gear foot on brake. Random square waves of 2-4VAC and erratic intervals. Put truck in park, let off brake. Graph stabilizes to a few millivolts AC. Apply brake while still in park, the 2-4VAC random square waves come back.

Put truck in 1st again, see same with brake applied. Let off to idle in gear. Speedo ~4mph, very clean rounded sine waveform, 0.73-0.78VAC.

Truck back up to 10mph on speedo, still very clean rounded sine waveform, 1.67-1.74VAC.

Tried this process 4 times, from truck off to start and test cycle to try and get computer to record codes. No flashing OD light or codes stored according to FORScan after the 4th attempt.

My few questions are:
Go ahead and change VSS sensor?

Is the ABS feeding noise into the VSS circuit?

I've read about the importance of square waves for the VSS, do my sine waves point to a fault?

Is this a PSOM or PCM issue?

 

[Duper Suty]

Update #2:

Decided to go ahead and replace VSS sensor. New in box ohm'd to 1111

Truck is still on jackstands at this point. After install, went through the battery of tests again with the O'scope. No changes to sine waveform. Still rides approximately half a volt AC high as my understanding (10mph on speedo is reading 1.54-1.71VAC). While doing this the acceleration and shifting felt way different.

Decided to gauge the responsiveness and power of this new by doing a 5 second converter stall test. In drive it made it to about 1920rpm, reverse (after a cool down running in neutral for about 10 minutes) maybe 1860 or 1880rpm.

No flashing OD light or codes stored from this. I figured the sensor is what it needed after the wiring of the circuit was repaired and I finally got it all resolved.

Shut truck off to let trans cool for a handful of hours, get it on the ground off the jackstands.

After several hours pass I go to drive it around the block and no forward gears, only strong reverse again.

 

[trackspeeder]

No forward gears with working reverse is usually loose feed bolts. Electronic issues will not totally kill all forward gears.

 

[Duper Suty]

No forward gears with working reverse is usually loose feed bolts. Electronic issues will not totally kill all forward gears.

Another suggestion I received on a different forum site was forward clutch pack is bad and to drop pan to inspect for clutch material. I have yet to get to dropping the pan but if the damaged material is absent then I will turn my attention towards the feed bolts. Regardless of what I find I will post updates

 

[Rdnck84_03]

From my experience the fwd drum will kill reverse also. Not 100% on the fwd clutch causing that as i shattered thre fwd drum itself. But i had absolutely no movement.

James

 

[adrianspeeder]

Even with a total loss of PSOM function, it should bang through gears with a limp mode.

I’d keep the original VSS for it being a better quality of the new

These trucks are also hitting service life of the EEC with bleeding capacitors and burnt boards. Pull it out and remove the cover for an inspection.

Adrianspeeder

 

[Duper Suty]

Even with a total loss of PSOM function, it should bang through gears with a limp mode.

I’d keep the original VSS for it being a better quality of the new

These trucks are also hitting service life of the EEC with bleeding capacitors and burnt boards. Pull it out and remove the cover for an inspection.

Adrianspeeder

That was a thought I had, but I had to recently attempt to move the truck into a better position out of my yard into my driveway for a tow to a new house (now currently in the middle of moving house) and I attempted to put the shift selector into 1st and then jump the 1st gear solenoid with 12v to bypass the ECM input, and it initially lurched as it "grabbed" the gear but still requires massive amounts of rpm to just weakly creep forward. Across the forums I've posted this same issue in, the current direction is to pull the pan off and look in it for forward drum or forward clutch material. I will be sure to do that once it gets to the new house and we get settled in.