My Tach is lying to me
 

06 F350 single wheel just out of warranty. Tach is off by oh.....say 25%. This just started today on my way back from a 450 mi. round trip. It still works but it's reading low like it's got 4 input signals and one of them is missing. Am I even close? Then another hundred miles down the road I had to brake kind of hard and the dang ABS light came on. I'll plug in a scanner (snap-on Solus) tomorrow if I can make the time. I don't know if the two problems are related or not. I'm sure someone has seen it before, because these things are so dang predictable. :argh:

Yes they are tied together through a relay/circuit. It's probably a bad connection at a relay or it could be the ABS module is gone. I've not experienced this problem yet, but doing a little research I found multiple issues regarding faulty tach readings with ABS light coming on. Have you done anything to the truck lately that might have caused a plug to come loose or damage wires?

Sometimes it's as simple as taking the sensor out of the rear-end (it's bolted in right on top) and cleaning it up or replacing that.

Sorry guys
 

I couldn't log on for what ever reason and the reset gave me double barrel hell. I didn't hae time to hook up scanner yesterday, but the tach started working and the ABS light went off about a half mile from the house. Sounds like a connection problem huh. E han't done anything to the truck lately. The dealer put a new FICM and pressure regulator on it a few months back so I don't think it took that long to manifest, but then I'm at the very beginning of the learning curve and have a long way to go. I drove my '89 7.3 for so long that i got stuck in the past. Technology shot right by me.
I recently bought a '92 dodge cummins. My plans are to rob the motor and drop it in the 89 F250 4X4. (just to let you guys know i'm not totally inept with a wrench in my hand) I've completely rebuilt the undercarriage and it's on it's 2nd motor and 2nd front end (small crash). Every seal, bearing, bushing, u-joint, caliper, rotor....well you get the picture. I just got fed up with not being able to pop the hood on the side of the highway walk up and down the fence row looking for some baling wire and jury rigging whatever and going on about my business. I thank you guys for getting back to me in such a timely manner and apologize again for my tardy response. I'll get to work on the 6.0L and pass on the info.

My buddies truck used to do the exact same thing... check that sensor on the pumpkin. I believe it's actually magnetic in order to pick up the debris coming off of the ring gears, but obviously over time collecting metal shavings on a sensor will do funny things.... like make ABS light come on and speedo/tach not working right... though I think the tach is not related to that, just the speedo is...

Sounds like a quick and easy task...might even give me a look at the condition of gears. Thanks everyone so much. It's hard to imagine strangers from all over coming together to help each other. I really appreciate it!

Well we haven't fixed your problem yet, but we're trying. Oh and didn't you read the disclaimer when you singed up where you have to buy us all beer, even if it doesn't work? :c:

Welcome to the site! :tu:

not a problem! I like beer! My favorite kind is O P..........(other peoples)
oh... and as long as we're on the subject..........at about 99500 miles my engine started taking a bit longer to fire. It went from a 3 second crank to 5-6 seconds. It just started all at once, and now it consistently takes 5-6 and sometimes 7 seconds to fire. What is this a precursor to? High pressure oil pump? Mileage is at 100800 right now. I've changed the oil religiously every 100 hrs. and taken good care of air filter and fuel filters. I don't work it very hard at all, but do hook on to trailers every now and then. I don't even have a 5th wheel ball in the bed.

Really hard to say why it takes a few seconds longer, but believe it or not simple little things can affect these temperamental beasts. Have you switched oils lately 15w-40/5w-40 etc...? I'm using RevX which I added with my oil and it seems to help engine start up. You might want to review the advertisement on it. :c:

Might have a small high pressure oil leak devloping... hard to say.

Just got back from a test run and I was thinking about your post and how long it took to start. Cold engine start took two secs. on my truck.

have used Rotella 15-40 from the get go and kept it changed just because of the high pressure oil pump. I heard they were expensive and liked clean oil. When it started it was like flipping a switch. One day it just took longer to fire. I had a "oh chit moment" in my head and was about to let off the key when it fired. ( i thought it wasn't going to fire) it's been that way every since. I finally got caught up around here.. I'm going to go see if I have the right key for my scanner and see if it threw any codes........it hasn't acted up again since sunday.................we'll see

Well we live in the same neck of the woods and I switched to Rotella T6 5w-40, but I just got finished overhauling the top end on mine. Mine used to take a lot longer in starting, but honestly I can't say the oil or the Revx specifically were the reason for such improvement.

Does it actually crank slower, or still crank the same speed and just not fire right away? Really would be nice to get a scanner on it and measure your ICP values

starter spins motor over at same speed. just takes longer to fire . ICP Values I'll have to check . I saw more acronyms than I could shake a stick at, but it did throw a couple of codes just a while ago.........C1175 and C1236 both point at LR speed sensor input circuit.....LR (left rear) surely not .... only wire I saw was the sensor on top of the 3rd member...(brain gears grinding) ABS sensors are on each wheel? or does sensor read ......no that couldn't be
I do have a scanner ........... I'll go hook it back up

---AutoMerged DoublePost---

ICP V = .26
ICP press = 0
ICP DSD = o

what does ICP stand for?

---AutoMerged DoublePost---

wow big difference when you start it...ICP V = .89 roughly
ICP Dsd rock solid at idle 4000
ICP Press slightly less
both increased proportionally with RPM

Will this help?
Also ICP is injector control pressure switch.

Hope this helps.
Also ICP is injector control pressure switch.


Attachment 18685

I was guessing injector control pressure.......would've never guessed the switch part. My scanner reads in kPa.......I'll have to research that. I've still got scanner hooked up and will continue to monitor while brain approaches saturation level.
thanks everybody