Hi,
I recently bought this ALDL cable from TPI Parts and I believe it's based on the 2-transistor ALDL interface. I've just tried hooking up my laptop to the car using a PL-2303 USB<->RS-232 converter but I'm unable to get it to work with any applications and would like some help on how to proceed to locate the problem. I have an '88 Camaro 350 TPI with the 1227165 ECM (according to the label on it at least).

All the tests in ALDLTest v200 fail. (Both fast and extended)

When running TTS Datamaster (DM35x32) it says that it has connected a working cable but is unable to communicate with the PCM.

EFILive V4 reports:
37:44.754: Scanning for heartbeat and chatter frames...
37:44.754: Waiting for Aldl bus silence of at least 50ms...
37:44.805: Start reading frame
37:45.005: Com timeout: Expecting frame header byte
37:45.011: No chatter found

39:03.511: Opening COM3 8228,8,N,1
39:12.648: Check vehicle interface...
39:12.653: Waiting for Aldl bus silence of at least 50ms...
39:12.703: Requesting Max232 interface to acknowlege: $FF,$55,$AC...
39:12.703: Start writing frame
39:12.703: Send: $FF,$55,$AC
39:12.704: Finished writing frame
39:12.704: Wait 10 ms after writing, before reading...
39:12.714: Start reading frame
39:12.814: Com timeout: Expecting frame header byte
39:12.825: No response from Max232
39:12.825: Retrying Max232 detection...

39:12.825: Waiting for Aldl bus silence of at least 50ms...
39:12.876: Requesting Max232 interface to acknowlege: $FF,$55,$AC...
39:12.876: Start writing frame
39:12.876: Send: $FF,$55,$AC
39:12.876: Finished writing frame
39:12.876: Wait 10 ms after writing, before reading...
39:12.886: Start reading frame
39:12.986: Com timeout: Expecting frame header byte
39:13.001: No response from Max232
39:13.001: Retrying Max232 detection...

39:13.001: Waiting for Aldl bus silence of at least 50ms...
39:13.051: Requesting Max232 interface to acknowlege: $FF,$55,$AC...
39:13.051: Start writing frame
39:13.051: Send: $FF,$55,$AC
39:13.051: Finished writing frame
39:13.051: Wait 10 ms after writing, before reading...
39:13.061: Start reading frame
39:13.162: Com timeout: Expecting frame header byte
39:13.176: No response from Max232
39:13.176: Retrying Max232 detection...

39:13.176: Interface cannot be detected

39:13.184: Scanning for heartbeat and chatter frames...
39:13.184: Waiting for Aldl bus silence of at least 50ms...
39:13.234: Start reading frame
39:13.335: Com timeout: Expecting frame header byte
39:13.340: No chatter found

TunerPro RT simply says there is no cable connected.

I wanted to blame the ALDL cable first but since Datamaster said that it found a working cable I'm not sure anymore. I have checked the connection between the ALDL connector under the dash and the ECM and the wiring appears to be ok. Is there a simple way that I can rule out the ALDL part of the ECM isn't broken? I do not have easy access to an oscilloscope. :/
The car is running fine otherwise, except maybe once in every 10 times I start it when it idles very roughly which is what I wanted to debug using the ALDL cable. It is currently running on an ADS Superchip but I have the original one as well.

 

Could always do the paperclip in ALDL connector thingy to bring up the codes / Service engine light to confirm wiring / ECM correct.

"PL-2303 USB<->RS-232 converter "

Lots of people have reported problems using a ext serial / USB adapter.
I have a ALDL /USB cable with serial / USB software that works fine with both TP and Datamaster.
However Datamaster will often decide not to connect first few times.
Can you borrow a old laptop with a serial port to confirm cable / connection is working correctly

 

After some recommendations on my local Camaro forum I bought a slightly more expensive cable which has a built in USB interface and it works perfectly.