I have a 2002 Dodge Grand Caravan v6, 3.3. Everything is working fine when I drive...up until I stop. The speedometer goes down towards 0 when I am slowing, but when I come to a complete stop the problems begin. The speedometer jumps up to about 20 and sometimes moves all the way around and back when I am stopped. When it is doing this, I can hear what sounds like the gears shifting.

Now sometimes when I start driving again, everything is fine. But sometimes the car goes into the Fail Safe mode and stops shifting. If it's in Fail Safe mode, when I park, it's been out of Fail Safe mode when I restart the car...for a while at least...until the problems begin again.

A few mechanics have looked at it and tell me the transmission is fine. Some friends have told me to replace the cluster, or to replace the speed sensor.

Kind of aggrevating that I can't seem to get rid of this issue. Does anyone here have any ideas of what I should try?

Thank you!

Ron

 

Typical symptoms for a failing output speed sensor. Erratic speedo AND shifting. This sensor is the reference source for the speedo and the tranny uses it for shift scheduling. Just be aware most of the time the sensor is at fault but these can turn into pricey wiring or TCM issues. The sensor should cost around $25. Are you seeing a check engine light and have you checked for codes?

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I replaced the Output Speed Sensor...initially it started working better, but then fell into it's old habits. I took it to Pep Boys and got it checked for codes and it came up with P0732, P0720, P0731 and P0700.

Here is some of the history...when this started happening we had it checked out and got a P0732, P0731, P0720 and a P0790.Transmission shop checked it out and replaced with a new module bought from the dealer. The problems still persisted and they said it must be something electrical. Another mechanic has looked at it and said the cluster is probably bad and should be replaced. Another mechanic says it's the Can Bus? Everyone has said the transmission is fine and is an electrical issue somewhere. but no one can seem to nail where exactly.

Really kind of frustrating! Don't know what the next step should be?

 

P0720 = Output speed sensor circuit fault
P0731/32 = Gear ratio error codes (can indicate output sensor problem)
P0700 = Just the PCM telling you the TCM has detected and stored a fault code.

Tell the mechanic that told you it's a "CAN" bus fault he's a generation off. Your van uses the PCI data bus. CAN bus is found on 5th generation vans 2008 and up. A cluster won't generate your codes or cause erratic shifting. I'll assume the "new module" was a TCM.

Only thing left is to test the wiring from the sensor to the TCM using a multimeter and visually inspect it for any signs of damage. Almost don't even won't to mention this but on very rare occasion (twice in 8 years) I've read of an input speed sensor fixing similar problems. No explanation. It just did.