Problem Datalogging 90 ECU

[esfry]

Hello,

New to DSM's and I am unsure if this is a common thing or no.

I have heard that 90 ECU's are sometimes not capable of datalogging.

Actually I want to use MMcd and I have loaded the software and followed all the instructions.

I used a scope and found the "heartbeat" from the ECU in its normal running state, and I found that it goes away in diagnostic mode, which I believe is correct?

I also looked at the Palm and when I run MMcd and look at the RS232 output I measured the correct 520us pulse counts (1920 baud) for both RPM and Knock, I believe?

Using 1 stop bit, little endian, reverse logic, I found for example,
RPM = .520H,.520L,2.12H,.520L,1.08H in mSec = 010000100 in little endian

Read normally, this is 0010 0001 and a 0 for the stop bit = 21 Hex

According to MMcd this is the address for RPM request to the ECU.

I can also verify that both my passive and active cable are passing this exact data to the ECU. But the ECU does not appear to respond.

I have tried both putting the ECU into diagnostic mode before and after starting the car and connecting the cables before and after, but nothing gives.

Is there some other reason that can cause the ECU not to respond but still have a heartbeat?

Please help.

Eric

 

[steve]

It's not that 90 ECUs are sometimes not capable of datalogging but that many JDM ECUs your likely to run across don't.

I still highly suggest people consider JDM or any junk yard motors a parts kit for a rebuild. You usually want to modify the motor to match the car not the other way. The exception is with 90 cars, I'd make the changes to the car to support the 91+ style CAS, TB, and ISC. Getting the tach in the car to work right makes the ignition a wash that needs to be though about before changing, and you want to keep the 90 oil cooler if you have it.