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2003 Dodge Grand Caravan PCM, Cruise Control, and Coolant Temperature Failures

I have a 2003 Dodge Grand Caravan. This week I encountered the following:

First Symptoms

  1. Red Battery Light
  2. Check Engine Light

Action Taken
Since car is 9 years old with original battery, I replaced battery. Boy, that battery was really good.

Symptoms observed after battery installed

  1. Red Battery Light
  2. Check Engine Light
  3. 0 reading on Engine Temperature

Action Taken
Tightened battery cable nut and red battery light went out. Took car to local mechanic who found and reported –
“Code 1478/Battery Temp Sensor, tested/was overvoltage allowed (4.9 for more than 3.2 seconds). Sensor located internally in PCM. PCM will have to be replaced.”

Symptoms observed on drive home
Drove car home. On the way, the battery and check engine lights went out. Engine coolant temperature came up ¼ scale. Cruise control would not work. Later, during drive, the battery and check engine lights came back on, cruise control continued to be nonfunctional, engine temperature gauge went to 0.

Action Taken
Took car to local dealer who replaced the PCM at a cost of $605 for the part and $135 for labor.

Subsequent Observations
After 45 miles on the drive home the check engine light came on.
The car was driven 2 days later. Battery light came on for about 5 miles then went off; check engine light remained on for the entire drive (~40 miles); cruise control remained nonfunctional and coolant temperature indicator read about ¼ scale.

What is/are the likely cause(s) of all these problems and what can I do? We’ve had very few problems with this car to this point, but these issues are really getting expensive fast.

If all these problems occured after replacing the battery, then I think you should read this.


The temp sensor is not located in the PCM. If it was, how would it actually measure anything? Usually the PCM is one of the most reliable parts of any vehicle. There are no moving parts, and they are well protected against weather, temperature, etc. The only thing that can kill them is bad power surges or idiocy such as someone hooking up jumper cables backwards.

There could have been a power surge when the new battery was installed, but I suspect that Tester is on to something with his analysis.

Actually, the battery and check computer lights came first. Cables were hooked up right. I had not noticed the coolant temp or cruise control issues so I don’t know if they happened before the battery was replaced or not.

Cruise control usually does not work when the ECM light comes on. That’s a safety feature, I suspect, but that’s perfectly normal, a by product that can be ignored.

I suspect you may have a faulty alternator or a problem with the wiring to it that is causing the battery warning light to come on.

@Cougar +1 , nutty electrical stuff means usually weak battery and/or faulty alternator. My case in Subaru was spiking voltage due to poor regulator. It did all sorts of crazy stuff including puff of smoke underhood, weird error’s thrown on dash odometer, instrument panel not working or every light illuminating.