08 e-450 abs and trans shifting problem

[Steve Mutter]

it has c1237,the truck now gets its rear speed from oss sensor in trans,gone thru the pinpoint test d,found a ground loose on the stud on the left wheel well,still comes back,my oss and my vss will jump all over the place, has anyone run into this,I am just going to start to load test circuits if you have any tips or info that would be cool

[G. Bedford]

Gas engine with a Torq-Shift?

[Steve Mutter]

sorry its a diesel

[G. Bedford]

Okay, when I checked the diag tree in trans for OSS codes it gave D for gas and I for diesel, so I wondered. I didn't go further to see if there were any major differences in testing.

 

The VSS and OSS that go erratic for you are PID's, right? But both signals originate from the single sensor from what I read, so you still might have a single cause.

 

Let's see, the TSS+ISS share the same VRef and sig/rtn as the OSS on the wiring schematic, but don't seem to have concerns. Have you monitored those signals for comparison, in case they are funky too, but not as bad?

 

I would use my lab scope to see the actual signal being produced by the OSS and do a quick comparison to either TSS or ISS for shape and strength. I also would induce a signal with a signal simulator to see if the PCM still sees a erratic VSS/OSS with a known clean signal.

 

I don't remember if the diag tree considered the possibility the trigger wheel on the output shaft could be loose/wobbling causing an erratic signal. Can you put a finger or screwdriver on the trigger to see if it is tight?

 

Gotta go put the garbage out at the curb and head to work. Good luck!

[OHNO60]

had same issue with 08 e450! ended up being a bum pcm. mine was sending the iss and oss all wackey. replaced the pcm worked great from that point on!

[Steve Mutter]

ya I used the wrong pinpoint test,went thru it again and there about the same but only till you get to the pcm conectors,everything passes,load tested the oss circuits,because we are so busy(out of work by 10:00 am) I took off the rear tail off and inspected the trigger wheel,it looks good,I have a pcm on order but it is b/o usa with no stock so it will be at leat a week till I see it,thank for the info!

[Alex Bruene]

I had the exact same issue on a 2008, and also came to the conclusion it needed a PCM. I ordered one, which did not fix it. Turns out there was a wire broken inside the insulation right at the PCM connector that would make intermittent contact. I took a pin out of an old engine harness and spliced it in, since it was too close to the crimp to make a repair. Oh... the speedo would also hover around 40KPH when the vehcile was stationary when the concern was happening.

[Steve Mutter]

I don't know why but my pcm showed up today,that was to fast to be from the USA but anyhow,installed and road tested 20 km,pcm fixed it thanks for all the input

[G. Bedford]

Gotta love it when you can put another mark in the win column!