My friend has a 2005 Dakota 3.7L 2wd AT truck. I am trying to help her get it back on the road, after sitting due to the electrical issues. It has two problems, but I am not sure if they are connected. The truck does not throw any OBD II codes.

No. 1 is ERROR where the miles should be.
No. 2 is low voltage coming off of a brand new alternator. This is the second new alternator installed, as it was initially thought that was the issue. It will not charge the battery correctly.

Battery is fairly new -- 3 years old and holds a charge/tests OK.

I have a Chilton guide, which states the voltage regulator is inside the PCM, but it also states that there is a battery temp sensor that regulates the alternator's current output.

Is is more common for the problem to be with the PCM or the temp sensor?
I found a few posts where a gauge cluster replacement corrected the ERROR code, but can't find anything about the voltage output.

Any help would be greatly appreciated!

 

Right there.

These trucks are incredibly electrically-sensitive to batteries even just barely sub-par and dated (which, as reported countless times here in the past, still "test ok", but a replacement battery still fixes the electrical problem(s)/gremlin(s)).

"Low voltage coming off" a second new alternator "which will not charge the new battery correctly" is usually a dead-giveaway...It sounds like the dated battery is no longer allowing a proper system circuit and therefore proper system voltage level.

If it were me, I wouldn't do any more messing with the electrical system until I've tried a new battery to see if that fixes it.

 

Battery replacement should be the first step, as stated for the reasons above. Then, run a test of your instrument cluster (Posted below), maybe that will wake it back up. If the ERROR remains, a new cluster (Plenty on used ones on Ebay for pretty cheap) should remedy that issue. Pretty simple install too, just some left side pieces need to come off to access it. [Similar thread here]

Try this test for the cluster

SELF TEST

The instrument cluster self test will put the instrument cluster into its self-diagnostic mode. In this mode the instrument cluster can perform a self-diagnostic test that will confirm that the instrument cluster circuitry, the gauges, and the indicators are capable of operating as designed. During the self test the instrument cluster circuitry will position each of the gauge needles at various calibration points, illuminate all of the segments or portions in the Liquid Crystal Display (LCD) unit, and turn all of the indicators ON and OFF again.
Successful completion of the self test will confirm that the instrument cluster is operational. However, there may still be a problem with the CAN data bus, the Powertrain Control Module (PCM), the Totally Integrated Power Module (TIPM), the Transmission Control Module (TCM), the Occupant Restraint Controller (ORC), the Controller Anti-lock Brake (CAB), the Wireless Ignition Node (WIN) or the hardwired inputs to one of these electronic control modules. Use a diagnostic scan tool to diagnose these components. Refer to the appropriate diagnostic information.

1. Begin the test with the ignition switch in the OFF position.

2. Depress the odometer/trip odometer switch button.

3. While still holding the odometer/trip odometer switch button depressed, turn the ignition switch to the ON position, but do not start the engine.

4. Release the odometer/trip odometer switch button.

5. The instrument cluster will simultaneously begin to illuminate all of the operational segments in the LCD unit and perform a bulb check of each operational Light Emitting Diode (LED) indicator. The LCD segments and LED indicators remain illuminated as each gauge needle is swept to several calibration points and back. If a VFD segment or an LED indicator fails to illuminate, or if a gauge needle fails to sweep through the calibration points and back during this test, the instrument cluster must be replaced.

6. The self test is now completed. The instrument cluster will automatically exit the self-diagnostic mode and return to normal operation at the completion of the test. The self test will be aborted if the ignition switch is turned to the OFF position, or if a vehicle speed message indicating that the vehicle is moving is received from the PCM over the CAN data bus during the test.

7. Go back to Step #1to repeat the test, if necessary.

 

Thanks for the responses!

I did the cluster test and it still says error, even though all the lights and gauges were working. It briefly showed a number something like 05600 ? where the miles should be, but went back to error. After asking her about it, she said it has had the error message longer than it was having issues charging the battery, so I am assuming that these are separate.

I will work on the new battery first. It has been sitting for a few months and it was charged with a plug-in charger overnight.

Does the cluster issue effect anything else, other than not being able to read the mileage? Seems like an odd thing.

 

Excellent info here. Thanks!