ABS and LSPV

Hi there, me again. Lots of questions coming up as I go through the truck after recently buying it.

95 with ABS, The PO disconnected/cut the sensor on the FL wheel. All the components are still there but the system doesn’t work and has the dash light. I don’t really mind that much. I’ve been reading on here that the early ABS characteristics on these trucks are bad, and downright dangerous even. I think that I will likely leave it disconnected now that I know this. I am wondering - can someone explain what the LSPV does exactly and the effect that ABS has on it? Mine needs replacing but I’m just trying to get a better understanding of how these two components work together. TIA

 

The proportioning valve adjusts the amount of brake fluid pressure gets to the rear drums. When the truck is loaded down, the valve opens and allows more pressure through to compensate for the additional weight in the bed. When there is not load in the bed, that much pressure would likely cause the rear tires to lock more easily. I could see how a VERY improperly adjusted valve could cause the ABS to step in, but in practical terms thats not a problem.

ABS on the other hand has sensors in the wheels that determine if a wheel as locked up, and then modulates the brake pressure to allow that wheel to regain traction (but keeping it from locking up).

A lot of people disable or remove the ABS if they prefer no ABS, or their ABS is too costly to repair.

I think that's an over exaggeration. When the ABS starts modulating the pressure, it can feel like you can't stop-specifically when the ABS is out of sorts with a bad sensor, etc... this can happen when you're coming up behind another vehicle and cause an accident if you're not ready for it (slip into neutral and use the e brake). These are things that you should be prepared for anyway.

If it's not cost prohibitive to repair your abs system, you should. A properly functioning ABS system is not bad or dangerous.

 

Thanks for the explanation. So just confirming, the LSPV doesn’t actually get any information from the ABS module, they’re separate? So replacing my pv without fixing the abs in my truck won’t affect how the pv works?

I appreciate the advice about repairing the ABS, I’m going to read some more about it - I’d honestly love to test out a first gen *with* it functioning and know for myself before I dish out $200 on a new sensor but that’s probably pretty unlikely to happen. There’s got to be a way to fix my cut one but I don’t have the knowledge at this point to know how

 

Correct- the valve is a standalone mechanical device mounted above the rear axle on the drivers side frame rail. It doesn't receive any input from ANY ECU, ABS or otherwise. It's only controlled by the lever connecting it to the axle.

Do you have a reason to believe that the LSPV needs to be replaced?

If you have both sides of the cut sensor, and have soldering experience it's possible to resolder the connector back on. I would try that before spending more on it. Use marine grade heat shrink... solder and heat shrink each wire individually, as well as the over all cable.

You only know the ABS is "there" if a wheel locks up. I see you're in Canada, so it would more likely lock up in snowy conditions... but it's not something that kicks in while mall crawling.