The ABS light and brake light came on at the same time. I retrieved the diagnostic code and it is code four. I think the code is Open/Grounded RABS valve reset circuit.

Any suggestions on how to proceed to find the problem ?

Thanks

 

Hi la9 and welcome to FTE

What year is your truck?
Chances are the RABS valve is shot but it could the RABS module or wiring though too.

 

Truck is 1999

 

On RABS valve itself, with the connector disconnected, measure the resistance between RABS valve pin 2, circuit 535 (LB/RD) and ground.

Is the resistance greater than 10,000 ohms?
If not then replace the RABS valve.

If that's ok then check the RABS VALVE CIRCUIT INTEGRITY RESISTOR ......... Set multimeter to 200 k ohm scale.
On the valve, measure the resistance between RABS valve pin 2, circuit 535 (LB/RD) and pin 3, circuit 274 (BK/WH).

Is the resistance between 18 and 26 k ohms?
If not then install a new RABS valve.

If all that is ok then you have to check the wiring between the RABS valve and the module. If that checks out ok then you need a new module.

 

Still not sure but here is what I got. Pin 2 to ground was 224K ohms. The resistance between pin 2 and 3 showed 5.6K ohms. After plugging the cable back in the lights went out. Pulled the cable out both lights come on. Plugged it back in they went out. I'm going to get some contact cleaner and try that and see what happens.

It drove about 3 hours this morning and the lights stayed off till I got about 100 feet from my driveway of course.

I'm going to try the contact cleaner and if that doesn't work I'll change the RABS valve since pin 2 and 3 read the wrong ohmage. Unless you think I should do something different.

Thanks for the information it was what I was looking for.

 

It sounds like you're on the right track.
Let us know how it goes.

 

Here's an update.

Since it was cheap I went ahead and replaced the VSS sensor in the rear differential. Still have the problem which I thought would be the case but it was worth a shot for as much as it cost.

This is wierd. Didn't have any contact cleaner so I wiggled the RABS connector around to clean contacts, no luck. Put alchohol in the connector to clean it. Worked for about 50 miles. Got contact cleaner sprayed contacts and hasn't worked since.

Got a RABS valve today to try. I'll put it in tomorrow and see what happens. According to the manual it needs replaced by what I'm reading on the meter. I'm not sure exactly what the problem is yet. Maybe wiring maybe RABS valve but I'll keep trying and let you know. Seems to be in that general area though.

I'll be an expert on Rear Anti Lock Brakes by the time this is all over with.

If the rear brakes needed replaced would that make the abs and brake lights come on also ? I have no grinding or noises and the pedal feels fine so I have overlooked this area. I started looking at other issues since I was getting a code 4.

Just trying to keep coming up with ideas until I figure it out.

 

Rear brakes in need of replacing shouldn't cause your problems.
I'm betting on the RABS valve.
Of course I have been wrong once or twice before though
lol

 

I think you are right this time. ABS and Brake lights been off since I changed the RABS valve. Haven't gave it the full test yet though. So no bragging.

The BIG question I have now is when I bleed the brakes the driver side shot fluid almost to the other side of the truck. The passenger side just trickled. Unscrewed the brake line off the cylinder and more fluid came out than was coming out the bleeder but still doesn't have the pressure the driver's side does. The weird part is that I jacked it up spun the tire and had my boy hit the brake and both sides worked the same. Tire locked up and I couldn't budge it.

Is the pressure diference due to the RABS valve ?

Should I replace the wheel cylinder ?

It all seems to be working fine just way different brake pressures.


Thanks

 

Just finished the full test ride and here is the conclusion.

CODE 4 = Bad RABS valve