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Discussion Starter · #1 ·
99.5

I am on vacation. It's about 25-30 degrees outside. I go to start truck. WTS light comes on. I wait for it to go out. Truck seems to crank nicely. I see nothing on the tach. I swap to a CPS that I had in glovebox that was good when removed (15 or so yrs ago). No fun swapping CPS in nasty blizzard conditions. Still no reading on tach when cranking.

I see P1391-c and P1393-c in the error codes.

I have Forescan light on my android. What should I be looking at next. Need to get this thing started.

2 yrs ago 17k miles ago - all new allied injectors and OEM glow plugs and OEM UVCH harness.

2.5 yrs ago 19k miles ago - New NAPA ST36 relay installed.

Starter replaced with 6.7 starter in April of this year about 7k miles ago.

New batteries installed in January of this year. I checked voltage on batteries after first 3 tries at starting 12.53 volts. Now that I tried a few more times it was down to 12.25 volts.

Truck is usually very reliable with good maintenance procedures.
 

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Those codes are related to that sensor, you had a working unit before them, you changed out the CPS, no change, your model should bounce the RPM gage when cranking over, but doesnt. To me it seems that the unit likely is not getting a signal for rotation position. Considering that, were it me I would look for frayed, broken or pest chewed wires. It's kinda hard to really see good from the bottom, might be easier to slip the belt off where you can look it over from the top good with a light and mirror. If you can plug your engine heater in the GPs will cycle shorter and save your try it out battery charge.
 

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Discussion Starter · #3 ·
Problem fixed. It was the GPR. I guess I have the only 99.5 where a good CPS shows nothing on the tach when cranking. Spent a bunch of time swapping a CPS in blizzard like conditions.
 
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Discussion Starter · #5 ·
This is a resource I carry with me all the time in the truck. I thought it was a wonderful resource . . . until yesterday. It needs to be edited on the right side where it indicates bad CPS or wiring if the tach doesn't move while cranking. My tach wasn't moving, luckily I had a spare CPS. Proceeded to spend the next few hours in blizzard conditions changing the CPS, only to figure out that was not the problem.

What I discovered was that not seeing an indication on the tach doesn't automatically mean you have a bad CPS. I always knew that the later model 99-03 (I think mid 01 to 03) do not necessarily give a tach signal when cranking, but I don't recall reading that 99.5s could also be in that same category.

Bottom line is that the tach NOT moving is NOT a guarantee of a bad CPS. I am not sure why some move and others don't, but it was a frustrating experience to say the least.
 

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White '99.5 F250 SD XLT 4x2, 7.3PSD, 6spd, SuperCab, Short Bed - purchased Oct'05
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Prior to knowing of these flowcharts I had a similar experience. Having already had the bad CPS experience once and quickly fixing it thanks to knowledge gained from from this forum, I found myself in my work parking lot with what I thought was the same issue, years later. This time changing the CPS made no difference, so me and the truck "ubered" home on a rollback. A few minutes of internet time at home pointed me to the fuel bowl heating element and the blown fuse that also provides power to the engine computer. Unplugging the heater and replacing the fuse had me ready to go for the next work day.

Note: These are links back to a thread that I keep on non-routine maintenance events for my truck. They are to the events listed above, not sure why the visible text is off topic.


 

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99.5

I am on vacation. It's about 25-30 degrees outside. I go to start truck. WTS light comes on. I wait for it to go out. Truck seems to crank nicely. I see nothing on the tach. I swap to a CPS that I had in glovebox that was good when removed (15 or so yrs ago). No fun swapping CPS in nasty blizzard conditions. Still no reading on tach when cranking.

I see P1391-c and P1393-c in the error codes.

I have Forescan light on my android. What should I be looking at next. Need to get this thing started.

2 yrs ago 17k miles ago - all new allied injectors and OEM glow plugs and OEM UVCH harness.

2.5 yrs ago 19k miles ago - New NAPA ST36 relay installed.

Starter replaced with 6.7 starter in April of this year about 7k miles ago.

New batteries installed in January of this year. I checked voltage on batteries after first 3 tries at starting 12.53 volts. Now that I tried a few more times it was down to 12.25 volts.

Truck is usually very reliable with good maintenance procedures.
I‘ve had all these same repairs. I betcha it’s a glow plug relay giving you issues in the cold weather.
 

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Discussion Starter · #8 ·
I‘ve had all these same repairs. I betcha it’s a glow plug relay giving you issues in the cold weather.

This would be a bad bet for me to take if you read post #3 that i wrote above. It is always best to read the posts after the initial post.
 

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This is a resource I carry with me all the time in the truck. I thought it was a wonderful resource . . . until yesterday. It needs to be edited on the right side where it indicates bad CPS or wiring if the tach doesn't move while cranking. My tach wasn't moving, luckily I had a spare CPS. Proceeded to spend the next few hours in blizzard conditions changing the CPS, only to figure out that was not the problem.

What I discovered was that not seeing an indication on the tach doesn't automatically mean you have a bad CPS. I always knew that the later model 99-03 (I think mid 01 to 03) do not necessarily give a tach signal when cranking, but I don't recall reading that 99.5s could also be in that same category.

Bottom line is that the tach NOT moving is NOT a guarantee of a bad CPS. I am not sure why some move and others don't, but it was a frustrating experience to say the least.
It has evolved from an era where CPS was a chronic issue, relativly cheap and easy to take off the table. Your initial symptoms come with cam sensor related codes, you changed the CPS and were directed to the next cheap and easy step, simply inspect the wires. I have still a other cheap, easy and accurate step. Get a small digital volt meter that fits in the lighter socket and leave it there. If a cold engine no voltage drop condition was noted KOEO in 25 deg weather, that's a positive indication of no power to the GP's.
It's not a collection of clairvoyants, its remote diagnostics based on a users written descriptions, some descriptions are more accurate and non circular than others resulting in help faster, even when te help is by elimination process.
 
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Discussion Starter · #11 ·
It has evolved from an era where CPS was a chronic issue, relativly cheap and easy to take off the table. Your initial symptoms come with cam sensor related codes, you changed the CPS and were directed to the next cheap and easy step, simply inspect the wires. I have still a other cheap, easy and accurate step. Get a small digital volt meter that fits in the lighter socket and leave it there. If a cold engine no voltage drop condition was noted KOEO in 25 deg weather, that's a positive indication of no power to the GP's.
It's not a collection of clairvoyants, its remote diagnostics based on a users written descriptions, some descriptions are more accurate and non circular than others resulting in help faster, even when te help is by elimination process.

My initial symptoms did NOT come with a cam sensor related code. Not sure where you got that information.

Your recommendation of checking voltage at the lighter socket on a cold engine is an excellent piece of advice. If no voltage drop then you definitely a problem with GP circuit (wiring, GPs or GPR, or PCM). Had I done this first I would have saved the trouble of replacing the CPS. I knew this and should have done it, but when I didn't see the tach moving I immediately thought CPS. I have looked at the "flow chart" so many times and have read so many posts over the years that I knew that tach not moving = bad CPS. Well, I learned the hard way that the flow chart is wrong in that regards.
 

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"My initial symptoms did NOT come with a cam sensor related code. Not sure where you got that information."

Now you can be sure, it would be from your April 1st posting.

It's a process, I believe that all of us have second guessed ourselves about short cuts we didn't recognize at the time, I know I do. Look at it this way, you have gained experience that will help on other issues and to assist other drivers. That experience has value that is gained only one way, frustration, tenacity and grease under the fingernails.
 
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