Brakes and trans issues
 

The truck has a couple problems and I'm not sure which direction to go. I've done a lot of reading but need help. The problems are separate but might have something in common.

Here's the DTC...
P0503 VSS Intermittent/erratic/high
P0720 Output speed sensor circuit
C1234 Speed wheel RF input signal missing
C1148 Speed wheel sensor coherency fault

Whatever is throwing the p0720 is intermittent. When at a stop the OD light flashes. At takeoff it feels like it's going to stall then like the trans slips before it gets going. It has actually stalled once. When it gets to cruising speed the OD light quits blinking. During the drive cycle the Speedometer on torque pro wigs out, and when going into park the RPMs spike to about 1400. I measured resistance of both the OSS and the VSS, both are within specs.

Now for the brakes... This started two years ago after I replaced ball joints, hubs, and rotors. Everything seemed good, the truck braked good but the ABS light was always on. On the snow and ice the ABS doesn't work at all. Lately, but not often the ABS light will go out and the front left locks up. The sensors ohm okay, and I get .3 volts from the sensor with the wheels spinning.

Correct me if I'm wrong. Both the trans and the ABS share input from the VSS.
I don't know which direction to go here.
I don't have a breakout box or any other means to check the circuitry.

Any help is much appreciated.

All you need to check the circuits is an ohm meter and a jumper wire. Your problem is most likely a wiring issue.

So basically a continuity test between sensor connector and the source? The PCM connector? Is there a splice, or a 'common' problem area?

Yes, that's what you need to do. Remember to always probe the back side of the connector, never the side that makes the connection. Probing the connection can open the pins, causing an issue where one didn't exist previously.

Thank you Mark. How about the ABS? Where is the source? Looks like the drivers side goes into a big bundle under a fuse box. I can't see where the passenger side goes.

I don't know about where the ABS goes.

Any help with the ABS?

Anyone...?

I hate bumping my own thread but I could use some input.