DTC memory

[e*clipse]

I have been experiencing intermittent IMA warnings. Generally these are accompanied by battery pack recalibrations, low battery capacity, etc.

It's been difficult to bring it to the dealer w/ the IMA light on, because the IMA light would shut off before I could get the car to the dealer.

The dealer told me these codes are erased when the IMA light turn off.

In other words: CAR - HEAL theyself - and forget everything about thine illness!

My main question is: when the IMA light turns on, one would expect some error code to be stored in the ECU. Is this correct?

It seems strange to me that the Honda would erase error codes. My old 1996 VW diesel ECU will store codes indefinitely, until they are erased by the technician. Does the Honda have so little memory that it must erase error codes? This would make tracking intermittent errors very difficult.

The dealer claims he cannot print the codes from his scanner and the codes are not saved.

What is really happening?

[Eli]

That doesn't seem correct to me. AFAIK, the DTCs are stored until either the battery is pulled, or the car has determined the problem has gone away, which usually takes 1-3 drive cycles?

[02insight]

do they turn off by themselves while driving, or does it turn off after you turn the car off, then back on ?

[e*clipse]

Thank you for the replys!

The IMA light turns off/on while driving, probably depending on whether the pack is balanced or not.

Every time we leave it at the dealer, we turn it off and leave it with them.

The reason I'm asking this question is the ECU's on my cars from the mid 1990's will store (often unimportant) codes indefinetely. This can be very important for solving intermittent problems. Trouble codes require less than a couple bytes of memory.

One thing I've observed is that computer memory has gotten significantly cheaper, both on PC's and embedded microcontrollers. It seems to that ECU's developed for cars 10 years later than my 1990's cars should have more capability to store information, not less.

[Eli]

No, not because it's out of balance. A balance issue isn't going to correct itself without a grid charger.

It's probably throwing P1449's. Though I've only seen the IMA light turn off after a key-off in that case, not while driving...

[e*clipse]

Perhaps it's not out of balance - perhaps it cannot balance because of more serious problems, like the P1449.

The problem is the dealer says they cannot find a problem, even though it's showing classic signs of battery pack issues. I would like to get this fixed before the warranty runs out, but the dealer insists there is no problem. I think there should be a record of this in the trouble codes.

Yes, the IMA light has turned off while driving.

[retepsnikrep]

Interestingly since fiddling with the scs mode I have discovered the BCM and other modules do/may store codes that are not relayed via the ecm to the scangauge.

So I have no IMA light and no stored codes, but even after a BCM reset the SCS mode will still blink out old IMA battery failure codes for the car which are obviously stored from when it had an OEM battery.

[e*clipse]

For me, a Li-Ion pack is the holy grail. I am very impressed w/ your work on that.

For now, the Ni-Mh pack will buy some time.

Would you mind sharing details on the communication w/ the BCM?

[retepsnikrep]

I suggest you do some searches and read the many threads & posts on here about comms.

search for BCM gauge, analysing the BCM data, etc etc

[e*clipse]

Ok, that's way off topic anyway.

I do need to know whether trouble codes are deleted by the ECM or must be deleted by the technician with a scanner.