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Help please! Check Engine light just came on in my 2003 Dodge Caravan. It is giving the codes of P0601 and P1684

I have two weeks before my registration expires and need to figure this out in order to pass the inspection. I was in a car accident two years ago and had to have my PCM replaced so I don’t think the computer is the problem. I could be wrong though. Does anyone have some advice they could give me on how to trouble shoot what the exact problem is? Could it be my battery? I would like to know for sure if it’s the PCM before I buy a replacement. Thanks in advance for any help with this!

DTC P0601 = Internal failure of PCM

DTC P1684 = The battery has been disconnected in the last 50 starts.


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The P0601 = can also be caused by low voltage to the ECU/PCM

The P1684 = Could just be a bad battery connection which could also trigger the P0601

First thing I would try is cleaning the battery connections, The P1684 should not have triggered the CEL

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Disconnect both battery terminals and use a tool to clean the posts and terminals.

First remove the cables from the battery and use a wire brush to remove any corrosion and dirt from the battery posts and the cable terminals. There is a tool with a round wire brush for this purpose, found at any auto parts store for less than $10
Before connecting the cables, apply a coating of di-electric grease to the battery posts this will keep oxygen away from the connection so that it will not corrode as fast.


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It is my understanding that P1684 could be caused due to multiple power disconnects. Once power is restored it may take up to 50 engine starts for the error to reset. It normally does not happen when one changes the battery or simply disconnects a battery terminal for short periods of time, i.e to perform some work.

I would make sure that all your connectors between the battery and PCM are correctly seated. You may have a loose connection that causes a temporary (even a millisecond would be recorded by the PCM) loss of power to the PCM.

Since you said that you replaced the PCM a year ago, I would also be worried that you may have a bad one. Was it new or used? Still under warranty?

By the way, P0601 and P1684 are normally triggered together. P0601 saying there is a memory error and P1684 indicates the multiple power loss, but could also indicate a communication malfunction within the PCM.

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Thank you for the response. Yes, the replacement ECM is refurbished.

Thank you for the response. I disconnected my battery last night and theee was a good amount of corrosion on the positive terminal. I left it disconnected for an hour then reconnected it and the check engine light came on with the first start. This was different from when I disconnected it 3 days ago. Then, the check engine light was off when I started it up. I drove around the block and oarkednkt for an hour before I left again, and the light was back on.

I say all that to ask, could I be doing something wrong with this battery disconnect? Will the disconnect reset my ECM and my check engine light every time?

One more question if you can…

I’m concerned that if I take it to a mechanic that they will see P0601 and stop looking for problems and simply tell me I need a new ECM.

When I take it in, what should I ask them to do? Is there a way for the mechanic to identify where the problem exactly is? In my research it seems that there are a whole lot of things that will trigger a P0601, and the majority of actual P0601 causes have nothing to do with the ECM.

What should I ask the mechanic?

Each time I got a Chrysler product with P0601 PCM memory check sum error the fault returned immediately after being erased, the batteries were not leaking or failing and the connections were not neglected. The only fix was to replace the PCM.

Your refurbished PCM is 15 years old and subject to the same failure as others.

Did you clean the corrosion off? how about inside the cable clamp? What about the negative connection, and the connections at the other ends of the cables?

Both connections at the battery must be removed and the mating surfaces cleaned.

It is not that hard of a job to do!!!

With a good connection (after the cleaning)…then you can look to other faults.