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Discussion Starter · #1 · (Edited)
Hey everyone. First Post here. I have an 05 STS with the dreaded E55 ECM. Long story short I built a bench harness for it following the ECM pins for GM LAN Bus +/-, IGN Volt (all 3 of them) switched, Battery+ (12V) and Ground (Screw on the ecm enclsoure).

I’m using a 12V 1A power supply and pins 4,5 (GND) 6 (CAN HI +) 14 (CAN LO -) 16 (12V) on the OBDII connector.

The ECM pinouts are
GMLAN BUS- (55)
SER DATA BUS+ (23)
Battery+ (36)
IGN 1 VOLT (1,3,17) (Switched)

I’ve googled this extensively with only mixed answers as a result. A company out there makes a “standalone” cable. Much like what I have assembled. However, on the schematic the DLC connects to the IPM/PIC which is what sends the wakeup command (on the GMLAN BUS Wakeup pin) to the appropriate module.

I have yet to trace the wakeup wire with a multimeter and see if I can wake the ECM with PWM on the bench harness.

Tried using a 120ohm resistor which resulted in 60ohms on the CAN BUS lines, still could not communicate with the ECM.

If anyone has any ideas? Something I am most likely overlooking? Any input would be much appreciated. Let me know if you need the ECM diagram for the 05 STS V6 and I can post them.

Kind regards,
GG
 

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Discussion Starter · #2 · (Edited)
UPDATE:
Left the 120ohm resistor connected between CAN HI and CAN LO which gives 60ohms across the CAN BUS lines; which is expected.
Tried sending 12V to the “Data Wake Up“ (ECM PIN 58) which still results in “No communications”.

Quite the battle for simple CAN communications...
588850


UPDATE #2:
I have surrendered the task of bench flashing this ECM for the time being...unless someone knows how to wake these ECMs up.
 
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