I have a 1998 Durango with the 5.9L motor and 4wd, have had it for about a year now. While driving yesterday out of nowhere it stopped shifting when in drive, and the brake light on the dash has been on since before I bought the truck. I was able to manually shift from 1st to 2nd with delays and hard shift. After getting to where I needed to go yesterday check engine light came on with the P1756 code. I was reading of someone else having the similar problem with a 99 ram 1500 same motor, and they changed the speed sensor and the problem went away. I watched some videos and what I can gather the speed sensor is on the center of the rear axle, put my volt meter on it and it had very little voltage (less than 2 volts), could this be the problem? I have to be careful of what I spend so I am trying to not change what is not needed to keep her running correctly.

 

No easy fix. P-code points to trans internals.

 

I hooked up to a good scan tool and this is what it showed, I am thinking to start with a transmission service, and possibly the governor pressure sensor.P1756A/T Governor Pressure Not Equal To Target At 15-20 PSI

 

Both output shaft sensor and rear wheel speed sensor generate a signal internally. They do not rely on external 12V or 5V. If your rear wheel sensor was not working, your speedo would probably only work above 20mph and eventually the ABS light and brake light would come on and stay on.

If your brake light has been on since you got the truck, maybe the ABS light wants to be on, too; however, it may be broken or was removed by a previous owner. The yellow ABS light in the cluster is an actual light bulb and easy to remove. The brake light, however, is an LED. Removing it requires further disassembly of the gauge cluster. A previous owner attempting to hide the non-functional ABS might have removed the yellow ABS light, but was not bold enough to snip off the red brake light LED.

Ensure the ABS light comes on momentarily during self-test when you turn the key from off to ignition. If it does not come on at all, replace the ABS light bulb. Assuming once the light bulb is replaced, comes on during self-test, and both ABS and brake light stay on, chances are good the rear wheel speed sensor or its wiring to the CAB is indeed broken. You can have the CAB codes read by a shop. Results will include why ABS does not work (rear wheel sensors, front hub sensors, other).

If the rear wheel speed sensor is excluded as culprit, let's move on to transmission basics:

1. In a 98 Durango the governor pressure sensor value is determined by the PCM by supplying 5V and reading back the sensor voltage in relation to a common ground. Whenever the governor pressure sensor is involved, ensure the transmission has a good ground to the chassis. I have an additional ground strap from transmission to the cross member. Also ensure the wiring from the PCM to the transmission is in good order, i.e. not chafed, stripped or pinched. Ensure the connectors are clean and properly seated.
2. Your Durango has a transmission throttle valve cable. Ensure it is properly adjusted. Ensure it is not binding.
3. Ensure proper fluid level.
4. Ensure front band and rear band are properly adjusted.

Whenever the governor line pressure is low, this can be related to a sticky regulator valve, a clogged filter, a worn pump. If you have time but no money I recommend:

1. Ensure fluid is clean, free from residue and not burnt
2. Ensure filter is clean.
3. Ensure transmission fluid cooler and lines are free from obstruction.
4. Ensure transmission fluid cooler and lines do not have pin holes through which air could be sucked into the fluid. Aerated fluid will cause erratic governor pressure readings.
5. Inspect valve body for stuck valves.
6. Ensure governor valve isn't sticking (remove governor, clean, inspect, repair).
7. Pressure test at pressure ports for further diagnosis.

If all this checks out, try a new governor pressure sensor.

Please let me know how this plays out, I am curious.

 

Both output shaft sensor and rear wheel speed sensor generate a signal internally. They do not rely on external 12V or 5V. If your rear wheel sensor was not working, your speedo would probably only work above 20mph and eventually the ABS light and brake light would come on and stay on.

If your brake light has been on since you got the truck, maybe the ABS light wants to be on, too; however, it may be broken or was removed by a previous owner. The yellow ABS light in the cluster is an actual light bulb and easy to remove. The brake light, however, is an LED. Removing it requires further disassembly of the gauge cluster. A previous owner attempting to hide the non-functional ABS might have removed the yellow ABS light, but was not bold enough to snip off the red brake light LED.

Ensure the ABS light comes on momentarily during self-test when you turn the key from off to ignition. If it does not come on at all, replace the ABS light bulb. Assuming once the light bulb is replaced, comes on during self-test, and both ABS and brake light stay on, chances are good the rear wheel speed sensor or its wiring to the CAB is indeed broken. You can have the CAB codes read by a shop. Results will include why ABS does not work (rear wheel sensors, front hub sensors, other).

If the rear wheel speed sensor is excluded as culprit, let's move on to transmission basics:

1. In a 98 Durango the governor pressure sensor value is determined by the PCM by supplying 5V and reading back the sensor voltage in relation to a common ground. Whenever the governor pressure sensor is involved, ensure the transmission has a good ground to the chassis. I have an additional ground strap from transmission to the cross member. Also ensure the wiring from the PCM to the transmission is in good order, i.e. not chafed, stripped or pinched. Ensure the connectors are clean and properly seated.
2. Your Durango has a transmission throttle valve cable. Ensure it is properly adjusted. Ensure it is not binding.
3. Ensure proper fluid level.
4. Ensure front band and rear band are properly adjusted.

Whenever the governor line pressure is low, this can be related to a sticky regulator valve, a clogged filter, a worn pump. If you have time but no money, I recommend:

1. Ensure fluid is clean, free from residue and not burnt
2. Ensure filter is clean.
3. Ensure transmission fluid cooler and lines are free from obstruction.
4. Ensure transmission fluid cooler and lines do not have pin holes through which air could be sucked into the fluid. Aerated fluid will cause erratic governor pressure readings.
5. Inspect valve body for stuck valves.
6. Ensure governor valve isn't sticking (remove governor, clean, inspect, repair).
7. Pressure test at pressure ports for further diagnosis.

If all this checks out, try a new governor pressure sensor.

Let us know how this plays out, please. I am curious.