LB7: P0727 help

[Harbin_22]

Swapped a trans that was slipping in 5th gear. New trans is built with Suncoast converter. Getting the P0727 immediately at start up. Tried new sensors, tried swapping TCM, checked all the wiring, no shorts no open. What's weird is everything on a scanner looks great. Turbine speed is steady, ISS steady, output speeds steady. Anyone ever dealt with this and fixed it. Did a lot of searching with most being dead ends.

 

[Mike L.]

That's engine speed sensor on the bell housing. You might have a bad dimple on the converter as that is the sensors signal point. Sensor might not be clocked ( bracket position ). Swap the turbine and bell housing sensors and see if anything changes.

 

[Harbin_22]

Thanks Mike, sensors were both changed, clocked correctly, and swapped with each other. Not looking like there is anyway to check the dimples on the converter other than pull the trans. Weird that the data feeds in the scanner are smooth and correct.

 

[Mike L.]

4L80 ss can be substituted and it doesn't care how you clock it. try machining the flange on the sensor to insert it deeper.

 

[Harbin_22]

Thanks Mike. Really running out of ideas

 

[Harbin_22]

Well figured it out. For anyone wondering, when the TCM loses that front sensor input signal, the TCM will use info from the ECM gathered rpm for turbine speed so it will still show turbine speed on a scanner. The real issue at hand was that alldata had the wire color and pin location at TCM backwards between the Turbine speed sensor and input shaft speed sensor. So we were ohming the input sensor from the TCM connector, which all checked out good. Once we figured out that info was wrong, found the correct pins at TCM, we had no continuity to the front sensor. Ended up being the pig tail at the turbine speed sensor was bad. Alot of headache for a $10 pigtail lol. Hope this helps someone in the future. Main thing is to me, it is dumb for live data in the TCM to be showing turbine speed when you have a fault code stating no signal, but it was using the ecm rpm to determine the turbine speed. Thanks for the help Mike

 

[Mike L.]

Glad you found it.:thumb:

 

[NC-smokinlmm]

Sounds like some shit I get to deal with. Way to stick with it...:thumb:

 

[Ne-max]

6.0 and 7.3 Powerstrokes do this same type of crap. Especially with the exhaust back pressure sensor and icp. Makes it a bich to diag.