I have 2003 Dodge Caravan 3.3. Recently I began having the intermittent jumping needle problem and experienced rough shifting sometimes when slowing down to a stop, and from a parked position rough shifting or hesitation when driving from parked / stop or going in reverse.

I have changed both sensors on the transmission (in and Speed/Out) and the problem persisted. I Did the speedometer instrument diagnostic and only got the code 400.1 (improper shutdown). I just went and got a code scanner for the the transmission and pulled the following codes

p0700 Electronic Automatic Transaxle Controller Diagnostic Trouble Present,
p0720Output Shaft Speed Circuit Malfunction,
p1790 Malfunction Immediately After Shift, p0720 Output Shaft Speed Sensor Malfunction,
p0731 First Gear Incorrect Ratio.

I then cleared all the codes. Drove home from Autozone, and ran the instrument diagnostic again and got 100.2,100.3,100.4 and 400.1

Thoughts? I think some of those codes were old and resolved by sensor change so I am waiting to see if they come back in the next day or so. Is my TCM most likely the culprit if the problem is persisting? Transmission seems fine when driving otherwise. These intermittent problems mostly occur when parked.

 

These are instrument cluster/PCI data bus fault codes and their meanings. To get powertrain codes as you get with a typical scanner cycle the key from off to on/run three times within 5 seconds then read the codes off the odometer display.

100.0 LOOP-BACK FAILURE
100.1 ABS COMMUNICATION FAULT
100.2 BCM COMMUNICATION FAULT - BCM is bolted to the firewall left of the brake pedal
100.3 EATX COMMUNICATION FAULT - EATX = Electronic Automatic Transaxle - likely the TCM
100.4 FCM COMMUNICATION FAULT - FCM is the silver box bolted to the fuse box/PDC/IPM
100.5 ORC COMMUNICATION FAULT
100.6 SBEC/DEC/MCM COMMUNICATION FAULT
200.0 AIRBAG LED SHORT
200.1 AIRBAG LED OPEN
200.2 ABS LED SHORT
200.3 ABS LED OPEN
200.6 EL INVERTER TIME-OUT
200.7 EATX MISMATCH
400.0 EEPROM READ/WRITE FAILURE
400.1 IMPROPER POWER DOWN DETECTED

Based on your code cluster code results you appear to have PCI data bus faults. Good bet they are associated with your problem. Unfortunately I've never found a troubleshooting tree associated with these codes. Without it the best you can do is inspect all the associated wiring and connections.

An erratic speedo with shift problems is a clear sign of a bad output sensor circuit. The P0720 code backs that up. Changing the sensors was the first logical step after inspecting connections. Unfortunately, that can lead to a TCM change if the sensors don't fix it or you don't find something obvious in the wire harness.

Make sure your battery is healthy and connections are clean and tight.

 

After driving a day, and still experiencing the needle jumping and some eratic shifting from a stop (like backing out of the driveway) I went and ran the codes again since I had cleared them.

I got the p0700 and p0720. So I will look very carefully at the wireing. Since it is only a problem when sitting still, and normalizes when I drive, i tend to think its also the tcm and not the solenoid. if it were the solenoid I would have trouble shifting etc right?

Incidently, this started happening on a road trip when after about 4 hours of driving I stoped at a gas station. When i started up again i heard a terrible whir that I believe is the alternator, or the cluctch pully on the alternator. I am checking that tomorrow and possibly replacing it depending on its condition. Could an alternator problem cause this situation with the tcm? its an old car at 130k, im inclined to think i just have 2 problems that arent related.

I checked ground strap at input sensor next to engine block, it seemed fine. Is there another?

Ill keep posting back what I find.

 

Ok, problem has been solved completely.

The alternator, though still functional (it still seemed to provided charging) it was providing irregular power to the battery. The meter would not show this, but the fluctating power situation must have been affecting the TCM causing the unit to throw up bad codes etc.

At first I suspected only the decoupler pully was bad, but just replaced the whole unit and now there are no more TCM issues. So many posts talked about cheching the harness, checking the grounds, it makes sense that if the power flow is irregular from the alternator, it would also cause problems for the TCM.

 

If you are getting a output sensor code when sitting and Idling, sure it could be an alternator problem. But if you are getting a output sensor code while driving. Then I would look at the sensor or the wires.

 

Nice work. Thanks for posting the fix.