Hey guys,

I have the following problem on my 99 Lightning (Rear wheel drive):
The ABS light comes on sometimes, but not always. It always goes off after first check up when the ignition is turned on, so apparently it passes the self test at the beginning.
Then it will come on when I do not let the truck roll from stop, but use the accelerator. It used to be only when I hit the accelerator somewhat harder, but now it is always when I use it to get off an intersection or so. If I just let the truck roll and use the accelerator only slightly it will stay off.
Once the ABS light comes on it will stay on until the the ignition is turned off, which is normal I guess.

As the problem seems to have something to do with the drivetrain I assume that it is something on the ABS on the rear axle, since it is a rear wheel drive truck.

So I took out the rear ABS sensor from the diff housing and measured the electrical resistance of the sensor (sensor taken off the vehicle). The ohmmeter does not give any value, so the resistance is infinitely high (Of course I did check that the ohmmeter is working).
Does that mean the sensor is dust?

Hope you can tell me if the sensor is my problem. Thanks in advance for your help.

 

The ABS module is in the front of the truck inside the engine compartment.

 

Thanks for the reply, but I do not think there is anything wrong with the ABS module, but rather with the sensor parts on the rear axle for the reasons I laid out.

Question is: What electrical resistance should a rear axle ABS sensor have when you measure the ohms at the two pins on the sensor. Mine has very high resistance, and on the web I found the information that good ones have between 1.2k and 2k ohms. People that had a defective sensor report resistance of zero, but mine has the opposite (infinity). What is correct?

 

If it is open circuit, then I'd look for broken wiring.

 

Reread the first post.

 

glc, I forgot the rear is a diff mounted sensor, unlike the sensors for the front with the whips.

To the OP: If it is open circuit, likely it needs to be replaced. I looked it up, prices range from $19 to $25. Probably not a bad idea to just change it.

 

Thanks again for your suggestions.

I am still wondering if an open circuit inside the rear diff sensor is the typical symptom if the sensor is broken. Because as I said other people report zero resistance (short circuit) on broken sensors. I was asking myself if these people just did not have any value on their ohmmeter interpreting this as zero, but of course if you get nothing on there, it means an open circuit (infinitely high restistance). I am hoping that somebody can tell me about that.

I know the sensor is not expensive, but I am located in Germany, so to get the thing over here I will end up with a price around 40-50 bucks. And if somebody could tell me that what I found is the typical symptom (this sensors seems to be failing rather often if you look through the internet) before spending that money, that would be much appreciated. If it is I will give it a shot.

 

Have you looked at rockauto.com to see how much shipping is?

 

Just a short update: I was at my mechanic to read out the trouble codes yesterday. The scanner says that there is an open circuit at the rear abs sensor. So I ordered one and will change that once I have it over here, guess that will fix that issue.