I just purchased an 04 civic hybrid. The IMA light is on and shows 73-1 code (battery cell overheating). I have ohmed out the 3 thermistors and they are each around 13k ohms. I've also read that you can put 10k ohm resistors in place of the thermistors so I tried that as well and got the same code. I have checked the wiring and its good. What else would cause this code?

 

My condolences. I hope you got it cheap. I have an '03, 02 and 05 Insights, and I've owned 2X '06 HCH2. I wouldn't wish these things on my ex-wife.

You "read" wrong.

"73-1" is not a valid code.

By "73-1" I assume you blinked out the "73" code. 73 on a 2004 is a P1432 code.

It's highly likely your battery has failed. It's possible that the there is a battery and BCM/MCM mismatch, but that usually triggers P1569 or P0A80.

What were the 10 tap voltages?

 

Yea I definitely love my insight. I have a 2000. I got it pretty cheap. Bought to flip it. Guy put a reconditioned battery pack in and all the cells were within .1 volt from each other and seems well. All read 15v or 15.1v and total voltage was right around 150v. I took it out and apart thinking he or the company that reconditioned it may have missed something. Seemed good. I did find a connector that was broken. I took the connector off the old battery pack (depinned the wires) and put it on the new one. That seems to be the only code besides an O2 sensor. Sorry for the bad code, that's just what my scanner said.

 

What connector was broken?

 

The white 6 pin connector that the thermistors are in.

 

Confirm the code existed before the connector was replaced.

Given this new information, I'm more suspicious of a mismatch.

BCM/MCM and pack mismatch means the PTC circuit is not as expected.

OLD BCM/MCM needs the PTC circuit intact or a 20-30Ω resistor completing that circuit.

NEW BCM/MCM needs open circuit.

 

Will they have matching numbers to see if they are matched/mismatched? Can I just jumper it out with a 20-30 ohm resistor to test that?

 

Can't go by numbers. Old BCM/MCM can be flashed to new config.

For old BCM/MCM:
If the PTC strips are present and active, should already have 20-30ishΩ
If the PTC strips are absent, you need a 20-30Ω resistor. Note that it's much more permissive than that, but that range definitely works.

For new BCM/MCM:
If PTC strips are present and active, break the circuit somewhere.
If PTC strips are absent and resistor is in place, break the circuit somewhere.

 

I just picked up another 04 hybrid with a good working IMA. I'm thinking swapping out the BCM and MCM and seeing what that does. Is that something that can be done without programming?. The MCM is what's behind the BCM correct?

 

I ended up swapping just the BCM with the new civic I just got and it works now. I drove it around and no IMA light, full charge, regen and assist work as should. However I do not have auto stop. Engine temp is normal, no HVAC on, but never did auto stop, not once.