Electrical issues..now no speedo/odometer. wth?

[domeshot14]

Hey guys, before I explain my problem with the speedo here is a little rundown of recent happenings with the trucks electrical system. First off it is a 99 4x4 SOHC. The power locks don't lock unless locked from the switch by the rear lifgate, but they will unlock from any switch. Drivers door will unlock fine but has to be locked manually (?). ABS light came on 2 weeks after new hubs and sensors. Double checked them again and still nothing so I bought a rear ABS sensor from Autozone but haven't had an opportunity to crawl under the truck and replace it this winter. Just last week I installed a 12" Kicker subwoofer and 1250w Power Acoustic amp along with a new stereo. Everything was fine for a couple days then that's when the speedo/odometer started to function intermittently. Now it hardly works at all and when it does it's not very long. The CEL came on the other day but the next day I started it up and the CEL was gone without me doing a thing.

So my question is, does the rear speed sensor affect the speedo or is there another speed sensor on the truck that I should look for? Also, what would have thrown the CEL and then caused it to turn off by itself? I'm not sure if this has to do with the subwoofer/amp being installed or if it's just coincidental. For what it's worth I used 4 gauge wire for the amp power and ground, and a 100A inline fuse. If anyone has any suggestions please run them by me even if you're not 100% sure I would appreciate any help I can get.

 

[bobflood]

Lock switches is probably wiring thru bundles between door and body - very common to have breaks there. Since rear lock button works, relays, locks, etc are OK. My drivers lock button has not worked for years, but pass and rear buttons do. I just reach across to pass side, or use the remote if truck is not running.
Re drivers door lock - the various rods and connectors get messed up and the little yellow clip breaks. Search the threads - lots of info on these.
Sorry - No help on other issues - good luck.

 

[gmanpaint]

'99 Rear ABS sensor and VSS is one in the same. Since both systems are acting up, I think once you install the new one, everything will be working again.

 

[domeshot14]

'99 Rear ABS sensor and VSS is one in the same. Since both systems are acting up, I think once you install the new one, everything will be working again.

If I get a chance this weekend I might get under there and try to do that real quick since I already have the new sensor. I looked at it once before and it looked like there wasn't much room up there to move around but I'll see how it goes..hopefully not bad. Oh and the CEL came back on earlier tonight so I will be running to autozone to find out what's up.

 

[jeffdro]

Ya I am having the same problem and also have the new sensor. I have not gotten under the truck to try and locate the sensor but can you tell me where to look. Is it on the tranny or the transfer case?

 

[albi1cnobi1]

Speedo gets its signal from rear ABS(VSS) sensor. When you replace it check the connector. The pins may be corroded, mine were and kept blowing ABS fuse. When I replaced the sensor I didn't clean the pins and fuse was still blowing. Had to crawl back under and clean them. You are correct not much room under there, Thought I would save you some aggravation. Jeff it is on the top of the rear diff, just to the driver side of center.

 

[domeshot14]

Speedo gets its signal from rear ABS(VSS) sensor.

That's what I've heard from most people, but I've also heard the speedo gets its signal from a speed sensor on either the tranny or transfer case. Is that a year-specific thing? I took a quick glance at both the other day when I was changing the oil and didn't see anything of the like, unless I plain missed it. I have a new-in-the-box ABS sensor sitting in the truck that I will most likely replace tomorrow.

When your sensor went bad did the trans start to act up like it would shift at the wrong time? It was really noticeable yesterday and also the engine temp was almost pegged out, but then it would drop off to near normal temp, then rise again and drop a little. I'm hoping this is just a glitch and it's all related to the faulty sensor. I'm afraid to drive it far in case it really is overheating and not just a false reading.

 

[albi1cnobi1]

From late 98 on Ford switched from the transfer case output to the rear diff, so yeah it kind of is year specific. I didn't have any temp issues but I seem to remember having shift problems. The temp thing might be a glitch but once you replace that sensor you'll know for sure. Stranger things have happened. Also the stock gauges are somewhat unreliable.

 

[domeshot14]

Had the sensor replaced yesterday and it fixed the speedo and removed the CEL..but I'm still having shift problems mainly under heavy acceleration, as well as temp issues and a high idle. I'm completely lost as to what could cause this. I don't smell coolant at any point while driving either

 

[gmanpaint]

Reset the ECM buy disconnecting your battery for 10-20 mins. See if that does anything to help.

 

[domeshot14]

I tried that and it didn't do anything. Replacing the speed sensor only fixed my speedo so as for the shift problems and running hot I'm now at a total loss. One day the truck was running just fine and then the next day it was acting like this. I took it for another drive around town (~10 miles) a little bit ago and noticed that when I start the truck and drive for about 2-3 miles it will shift normally and run at its normal temp..then almost at random it will start to get hot and idle around 1300-1500rpm's. I know these things are notorious for doing some weird ****, and an oil change was the only thing I did to the truck between the time it last ran normally and when it started to act funny..and I don't see any way that could have caused these symptoms. Whatever it is if it requires tearing into the motor I think I will for sure have to part ways with this f---ing truck lol.