Speedo not working - loss of power

mromberg1

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So my last three trips towing my fifth wheel I've gotten the wrench light. I suspect it's an over boost. I monitor the boost with a scan-gauge and the last two times I got the light at around 29 psi. Pull over, shut down engine and all is good. I brought it to a local diesel mechanic who couldn't replicate the problem and found no codes. He asked me to hook up the trailer so he could test. He's an old school guy and to get the engine to temp he hammers down on the brake while in gear and revs the engine for about 30 seconds. During this process the engine goes into limp mode, no wrench light, and speedo doesn't work. He thinks that may be part of my problem. I'm not so sure as this has never happened under normal driving conditions. I suspect the engine revving at whatever Rpm's with out the vehicle moving trips something in the computer and triggers the limp mode and is completely unrelated to my turbo issue. And he can replicate the speedo issue without any problems. Thoughts?


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Zmann

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no speedo
loss of power

there should be a VSS code
it has happened to me occasionally
 

Zmann

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that WOT and in gear test sounds a tad brutal on the 5r110 ?

they have you check line pressure that way but warn you not to do it to long

my emissions testing is WOT in neutral for 3-5 seconds 3 times in a row it never set a wrench
 

mromberg1

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that WOT and in gear test sounds a tad brutal on the 5r110 ?

they have you check line pressure that way but warn you not to do it to long



No WOT but he was in the 3-4K rpm range I would guess.


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Zmann

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4k is WOT so he was close

see if this sounds like what your experiencing

my speedo will not show speed first thing in the morning while camping and having the trailer plug plugged into my slide in camper

the first time I did not notice and went to get on the freeway
truck was gutless and the folk behind me were passing me on the left of a two lane

so i hugged the right side . as soon as they got next to me my truck went warp speed
and the speedo came back

later code retrieval showed a VSS fault
I have since changed it with a new OEM unit but noticed the code again the other day
it has to be a trailer plug related issue?
 

mromberg1

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4k is WOT so he was close

see if this sounds like what your experiencing

my speedo will not show speed first thing in the morning while camping and having the trailer plug plugged into my slide in camper

the first time I did not notice and went to get on the freeway
truck was gutless and the folk behind me were passing me on the left of a two lane

so i hugged the right side . as soon as they got next to me my truck went warp speed
and the speedo came back

later code retrieval showed a VSS fault
I have since changed it with a new OEM unit but noticed the code again the other day
it has to be a trailer plug related issue?



The only time the speedo issue has happened is when the mechanic did the brake in gear throttle 'test'. Shut it off turn it back on it's good to go. I think this is unrelated to what I believe is a turbo overboost issue. We couldn't get the turbo to 29psi on our limited grade test yesterday.


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Zmann

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interesting

I can get 32 psi on my CTS and have yet to over boost code
maybe the tunes prevent that ?
 

Zmann

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i don't have my verion # handy
I just know it will limp for low fuel LOL

hope you get this dialed in
 

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