Hello all,

I have researched this issue and I have much info so please read the details below and let me know what you think. Also, I have the full set of five factory manuals and they actually have not helped me to this point.

I have 1999 dakota with 5.2 liter and a manual transmission.

Speedometer did not work when I bought it. Check engine, abs, and brake light are on.

We scanned codes, and got P0500 - speed sensor a malfunction.

I know this is normally is the sensor on the rear differential. However, we were told it was replaced once. We have checked its resistance, and it is 1994 ohms. Specs say the resistance should be between 1600 and 2300 ohms.

We decided to clear the codes and pull the connector off for this sensor. I want to see if the same code returns.

Does anyone have any idea if the front wheel abs sensors have anything to do with the speedometer?

Thanks!

dgilfillen

 

Hi,

The front speed sensors do not have any effect on the speedometer. P0500 is as you found, the rear axle speed sensor. Just because it has the correct resistance, it does not mean it will function.

Sometimes it gets coated with magnetic material from the differential. You could always pull it and inspect it.

How are the fuses for the ABS? The speed sensor signal comes from the anti-lock brake controller.

 

00DakDan,

Thanks for the reply!

I should have told you that I did pull the existing sensor in the differential. It had no magnetic particles from the differential on it. I do realize that does not mean it is working either, but I should have given you that info.

I will check all ABS fuses and report back.

Is there any good way to actually verify the sensor is working.... And... How can I verify the wiring to the sensor has no open circuits?

Does anyone know the pins at the PCM I should check? Or do these wires go another location than the PCM?

Thanks!

dgilfillen

 

The wiring from the speed sensors do not go to the PCM. They go to the ABS controller.

Do you have the wiring diagram?

You don't say it but I'm assuming you have 4 wheel ABS.

In '00, electrically they are very close to a '99, the rear wheel speed sensor goes to the ABS controller, Connector 1, pin 1 (red with violet tracer) and pin 8 (white with violet tracer) You can measure resistance from there. It should be the same as you read earlier.

Make sure the connectors are clean and tight.

Usually the sensor is just replaced if it doesn't work. Maybe the new one is damaged?

 

Mine isn't the same year as yours, but I have a speed sensor on the transfer case output shaft. Does yours have that? On mine, that's the one that works the speedometer.

 

Thanks again for more replies.

Mine is a 2wd, so no xfer case.

There are no other speed sensors except the rear one on the diff. There are two front abs sensors too (it does have 4 wheel abs).

I have read some other posts indicating that the abs module could be bad. Do you know the way to retrieve cluster codes on a 1999?

Thanks again!

dgilfillen

 

To pull codes from the instrument cluster try this:

1. Key off
2. Depress and hold the trip reset button down
3. While holding the button, turn the ignition ON - don't start
4. Continue holding the button for about 10 seconds until CHEC shows in the odometer window.

It'll run a self test of the cluster, do a gauge sweep and test the lights. Any faults will display in the odometer window.

A DRB (dealer) should be able to diagnose the problem easily. It can not only test bus communications but also read any faults you may have on the ABS module.

 

To add to my last post, most code readers do not scan ABS codes. If it is a problem with the ABS module. There should be a code stored if the ABS light is on though.