No crank

Jeffrey Technician California Posted   Latest   Edited  
Resolved
Electrical
Heavy Duty
2012 Ford F-550 Super Duty 6.8L
P0706 — Transmission Range Sensor "A" Circuit Range/Performance
P0707 — Transmission Range Sensor "A" Circuit Low
P1702
P1921
No Crank / No Start

1FD0W5HY1CEB… F550 6.8L v10 4R110W transmission 

When it will not crank it does not indicate park on dash also does not indicate P/N in PCM

as we have many of these trucks and spare parts the fallowing parts have been swapped with known good parts

Transmission wiring harness (external)

Transmission wiring harness (internal)

PCM (TCM) reflashed and security relearned 

Transmission range sensor (first thing replaced ‘new’)

Both speed sensors have been unplugged because the share wiring with the range switch so made sure they were not pulling down voltages.

Dash had been removed, so removed radio and kick panel removed to inspect BCM grounds.

In the process of scoping out signals from range sensor to PCM to check the difference between two of these trucks. But even so everything has been replaced in line from the range sensor to the PCM and at a bit of a loss on what the issue could be.

codes: 

P0706 Transmission range sensor A Range/Performance 

P0707 Transmission range sensor A circuit low

P1702 Transmission range sensor circuit intermittent 

P1921 Transmission range signal

I have this idea that power is not being fed to the sensor at times one wire should have battery voltage provided by the pcm but maybe that battery voltage isnt being fed into the pcm so it cant feed it out to the sensor be nice to know where it gets the power in that is then pushed out to the sensor has to be on the pcm side of the module as no power is provided as input on the tcm connector of the pcm. 

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John Diagnostician
Colorado
John
 

Does the pcm indicate park/neutral and cranking with the key in the cranking position?

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Jeffrey Technician
California
Jeffrey
 

No the no crank is 100% because it doesn't see the transmission range. Cranks starts when the range is correctly indicated. Looking at a scan tool when the no crank conditions is being experienced invalid is indicated under current range. At first moving the shifter from park to drive and back would bring it back to life.

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Missing Info
Joseph Technician
Pennsylvania
Joseph
 

Do you have reverse lights?

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Helpful
Jeffrey Technician
California
Jeffrey
 

No the range switch doesn’t read no signal so no reverse lamps just pinned the hole thing out again and everything is good tho now it has range signal so ill have to drive it and let in mess up again before I can continue

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Patrick Diagnostician
Michigan
Patrick
 

Looking at the wiring diagram, both speed sensors share power and ground with the trans range sensor. I would presume fault codes would set for both speed sensors if either those two signals faltered. I recommend scoping the TR-P sensor wire (CET22 GY-BN) at the PCM connector C175T pin 12. It is a 5 volt reference that will pulse width modulate at different frequencies in each gear. There is…

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Jeffrey Technician
California
Jeffrey
 

The 5 volt reference is there when plugged in vehicle in park it is 2.5v the ground is there vpwr assuming this is battery voltage as indicated by the information i have is not there. the color on the wires is not the same as the diagrams but this is being mesured at the pcm and the pcm feeds that 12v system voltage to the sensor but it must be one of the powers into the pcm on the pcm side…

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Maynard Owner/Technician
New Hampshire
Maynard
 

I had a 2009 f550 with no crank and on gear lights on, turned out to be rust in the ball socket at the end of the shift cable at the transmission shift lever was keeping it between park and reverse and not letting it crank. try moving the lever at the transmission a little by hand.

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Jeffrey Technician
California
Jeffrey
 

There is at times no power to the switch, its not between gears I kinda figured out what it is but its in a rats nest of power wires for the add ons in the rear passenger crew carrier and I ended up just cleaning all the connections seems to have solved the issue. Unfortunately there are no wiring diagrams for the accessories or I would describe this better.

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Jeffrey Technician
California
Jeffrey Resolution
   

This was caused by a seemingly unrelated wire, rubbed through in the loom, under the right front corner of the radiator on the lower core support. This had no relation shown in the wiring diagrams but was shorting the TCM side of the PCM. There was really no way to find this issue other then just pulling on everything even unrelated circuits and watching the cluster for the gear selection…

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