catfSSh

Lately my 2000 4wd silverado has been acting very weirdly. I can't get a final answer from anyone on what its problem is.

Truck has quite a bit of miles, and within the last 1,000 miles had a transmission swap.
It started by throwing an ABS light in the dash. It started running rough whenever the ABS light came on (erratic transmission, shaky speedo needle).

I got it tested and it threw a few codes all for two wheel speed sensors going bad, I replaced them both and took it back to the shop to get it rescanned and erase the old codes.
On the diagnostic, it throws no codes but the ABS light was on the whole 15 minute drive there and still driving like crap.

How can I figure out what is wrong with it since it won't throw codes?

I am thinking that the problem is probably big, either a complete ABS module gone bad, or something inside the trans not working right.

Fabrik8

Usually problems that don't show up immediately after startup are a sensor malfunction or a cracked tone ring. The E-brake switch is usually on your ebrake and shouldn't be affected by anything like what you're talking about, unless the problem is related to power or ground that is shared between more than one thing. I'd be willing to bet that the three problems are mechanically unrelated by electrically related.

This is going to destroy my brain trying to figure out what the common link is..

nismo

sh!ts weak.

catfSSh

I think I follow what you're saying. Since all three "flags" are going off at the same time, it is probably some electric failure somewhere in the system?

Fabrik8

Well, what I'm saying is that the speedometer, ABS system, and E-Brake switch aren't mechanically connected or anything like that, and they don't usually share signals. Therefore I think there is something electrically shared between them (like power, ground, etc.) that is affecting all three of them.

But....

Actually, I'll retract my previous statement. I guess it could stand to reason that the ABS system in your truck would use the E-brake input and vehicle speed input for something, so that could be related. I'm not sure how though. Usually ABS systems use the wheelspeed sensors for everything, and they don't care about the E-brake or the (transmission) vehicle speed sensor. Vehicle speed is already calculated by the ABS system using its own wheelspeed sensors, so that would be slightly redundant. Anyway, what I'm trying to say is that just because I don't know about it doesn't mean it doesn't exist. So I could be thinking about this all wrong.

catfSSh

So far, I'm leaning towards the shared electrical problem (bad ground).

I've seen a few posts on truck boards about that problem.




Hopefully soon I'll get an ABS diagnostic ran and can pinpoint it farther.



EDIT: that strange thing is, it ALL started happening after some light 4wd driving.

Fabrik8

Post up whatever you find, I'm really curious about what's going on here.

Could be a harness fatigue problem, or a loose ground. The 4WD is what made me think it could be a sensor or tone ring problem, basically something might have got shaken loose. I've had cracked tone rings on two different cars but I have no idea what your truck has for tone rings on it. I'm not really a truck guy.

nismo

i mean, the truck is 365,xxx deep....


shes a tank. lol

catfSSh

Soon I'll get an ABS diagnostic ran and post up what the problem is. The 4wd driving was pretty light though, just wet uphills so no real extreme stuff.


Haha yea, forgot to mention the truck has a shitton of miles.

catfSSh

I got it scanned yesterday. Came back with 5 codes all pertaining to the left front wheel speed sensor and rear wheel speed sensor.

The mechanic said it is weird that it brought back 5 codes for two sensors all at once, hinting at an electrical problem. He wasn't too much help, but I think I'll check all the wires first, then replacing the rear sensor.