1990 Legacy Hitachi ECU romid:703943

[b3lha]

Another one of Andrey's rom dumps. This one is from the Hitachi ECU of a 1990 Legacy. This TCU has a HD63B03YCP CPU and there is a separate 27C256 EPROM surrounded by a blue upgrade socket.

I have tried in vain to attach a disassembler listing from IDA-PRO, but this forum won't allow an attachment larger than 128K.

[b3lha]

Here is the hex dump.

[b3lha]

Here is a bzip2 archive containing the disassembled code:

[b3lha]

I finally found time to look at this. I think the fuel map is at C000 and the timing maps at C100 and C200. The parameters used to read these maps are RPM at address 140B and Engine Load at 1414.

I have also found the error codes at B2DA. Once I figure out the code that processes these error codes, it will lead me to some of the other parameters.

Phil.

[b3lha]

Hey Andrey,

I'm finding this ECU tricky, it's quite a lot different to the one's I've seen before.

I have some addresses for you to try.

Speed: 1507
Throttle: 1463
MAF voltage: 1400
Mass Airflow: 141E
Temperature: 1405 ?

RPM & Load as per my previous post.

The MAF values are actually 16bit and I've given the Most Significant Byte. This is probably what the Select Monitor uses.

Let me know how you get on.

Phil.

[b3lha]

Hey Andrey, if you are still here, I have a couple more to try:

I found the code that reads the Analogue to Digital Converters (voltage inputs)

Channel 1 is address 1402 or 1463 (TPS).
Channel 2 is address 1403. I think this is O2 sensor it stores Min and Max at 146E and 146F.
Channel 3 is address 1404. Unknown.
Channel 4 is address 1405 or 141A. The value is used in a graph and the result goes to 141B. This could be Coolant Temperature Sensor Voltage and Coolant Temperature.
Channel 5 is address 1406. Unknown.
Channels 6 and 7 are not used.
Channel 8 is address 1409. Might be knock sensor.

1404 or 1406 could be Battery Voltage.
.
There seems to be a pattern here: Address = 1401 + Channel Number.