MM3 Tuner - ECM Communication Error - Code 18504

**AK Bob** · 4 Weeks Ago

Originally Posted by Morbious

Is that testing done with a key on/off, or doesn't matter?

Are those measurements with a multimeter correct?

Thanks so much, you have been a major help!!!

My ECM erased itself, and nobody could tell me why.

I'm now wondering if it had something to do with TIPM going bad!

I replaced ECM but am unable to load a tune.

It loaded the first time I tried them, but the trans-tune wouldn't load.

I read somewhere that reloading the ECM tune worked, but when I tried that, it failed to write, and I've been stuck trying to reload the stock file minus one success.

Then, it failed to write a new tune, and I am now stuck trying to reload the stock file again.

Now, I can't communicate with ECM.

Probably a bricked ECM?

All measurements so far have been taken with a multimeter on volts DC.

When measuring the power and grounds, the key position doesn’t matter.

However, when measuring the CAN bus voltage, the key must be in the run position.

Unfortunately, I am not familiar with the CAN Bus topology layout on the 3rd Gens.

Looking at the limited information in the manual, it appears that the TIPM is the gateway, and you should be able to communicate with it directly from the OBD port.

The voltage checks on pins#6 &#14 with the key in the run position will at least verify that the OBD is connected and communicating with the TIPM.

It appears that the TIPM is the hub for the CAN bus and transmits to the ECM and other modules.

You may be unable to communicate with the ECM because of a failure in the TIPM.

https://tipmrebuilders.com/chrysler-...-tipm-failure/

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**Morbious** · 4 Weeks Ago

I'm getting 0.001 or 0.002 volts between 6 and 14 and 2.507 volts on both 6 and 14 connected to the ground!

I'm leaning toward bad TIPM.

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**AK Bob** · 4 Weeks Ago

Originally Posted by Morbious

I'm getting 0.001 or 0.002 volts between 6 and 14 and 2.507 volts on both 6 and 14 connected to the ground!

I'm leaning toward bad TIPM.

It would appear that your OBD port is connected to the TIPM and that it could indeed be bad.

One other check I recommend is measuring the resistance between pins 6 and 14 at the OBD with the batteries disconnected.

Generally, if the CAN bus wires are all in tact, you will measure approximately 60 Ohms.

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**Morbious** · 4 Weeks Ago

I'm getting 61.5.

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**AK Bob** · 4 Weeks Ago

Originally Posted by Morbious

I'm getting 61.5.

That's good.

It shows us that your CAN Bus circuit is physically intact, at least all the way to both of the modules with the terminating resistors.

I am thinking possibly a bad TIPM.

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