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I am trying to get my port to read the ECM? it sees the power, but does not/can not read the E38 ECM. OG donor is a 2013 chevy 2wd silverado. I have tried with HP Tuners and a 3rd party scan software as well. information: 2013 4.8LS with OG trans, ECM,TCM,fuse box and factory wires (X1-X5 connectors). the obd port is a 6 wire new canbus connector pinned as below: pin info: 2 20ga PPL CLASS 2 SERIAL DATA (is this the LS serial wake up pin 18 on my J1 connector?) 4 18ga BLK GROUND (bus bar on cab 5 18ga BLK GROUND (attached to chassis) 6 20ga TAN/BLK HSCAN (+) 14 20ga TAN HSCAN (-) 16 16ga ORN BATTERY (12V)
I am not able to get the obdii port to activate/read the ECM, any help would be greatly appreciated
nick, thank you for the reply. no the message is that the software can not "read/see" the ECM. it shows there is power, but that it is it. it doesn't show that there is a ECM connected. I was thinking that maybe someone who has done a similar swap could share what factory wires they used. I am not a electrical guy, but it seems very confusing....
The 60 ohm terminating circuit is on pins 6 & 14 and it passes through the OBD port. Starts at the fuel pump controller (with a 120 ohm resistor) and ends at the ECM (with a 120 ohm resistor). The resistors are wired in parallel and should read 60 ohms. It also passes through other devices like in my case, the electric steering, 6L80 trans controller and abs controller.
Here is the pinout for my port. You likely have an open between the fuel pump controller and the ECM. With the battery disconnected, check to see what the resistance is across pins 6 & 14. If you don't read 60 ohms, the circuit is open; either one or both of the 120 ohm resistor is absent.
nick, I will have a friend help me check out your suggestion as I am not a electrical person. I am also trying to confirm my pin locations related to the "new" GMcanbus protocol (I believed started in 2010 ECMs??)
Nick, according to lt1swap ECM pinout guide for my E38 ECM (2013 4.8 silverado) the "accessory wakeup serial data" is J1/X1 ECM connector: pin 18,curcuit 5985,dk blu wire (LSCAN in the 2013 engine diagram). I ran it from the X109 connector (same connector with the HSCAN+ & HSCAN- data wires and the 6 DBW pedal wires) into the firewall & soldered to the ITC BILLET 6 wire "new GM CANBUS " OBD2 port which is wired as stated above. I am not sure what "j1850" is?? the descriptions I have found indicate the dk blu wire is LSCAN data wire. I believe that HSCAN = HIGH SPEED CANBUS (+/-) and that LSCAN = low speed canbus... but I am unknowledgable about alot of this info. ....... I am getting this info from diagrams & internet
thank you for your time on my question
Last edited by rodstored-72; Nov 18, 2021 at 11:34 AM.
Looks like we're not talking about the same things. The pinout I posted above is for the under-dash OBD-II port. It's a standard and yours should only have 16 pins.
But you refer to pin 18 and it seems like you're referring to the OBD-II port??? Need to get on the same page...
Nick, aahhhh, I understand what you are saying. yea, what I basically am trying to find out what wires are needed from the ECM (e38 from 2013 silverado) to connect to the obd2 port. I believe that 6 wires need to run from the ECM to the 16 port OBD2 port. which I think are the 6 wires listed above in my first post. I THINK I have the right wires?, but not sure on the pin assignment to the OBD2 port for the 6 wires. I hope I am making sense... my wiring understanding is vary lacking. . again the port shows power, but it does not recognize the ECM..
thanks for your patience...
You have to check the resistance; there needs to be a complete circuit so that the two 120 ohm terminating resistors (one in the fuel pump controller and one in the ecm) register 60 ohms on pins 6 & 14 of the OBD port. If you don't see 60 ohms +-, the engine will never fire and the fuel pump will never run and the OBD port will never see anything...
Well…after more research & talking with my friend with the hp tuner software, I FINALLY figured out the correct pin assignments to read the ECM!... woo woo!! Below is the obdii port pin out. This is for a E38 ECM from a 2013 chevrolet Silverado.
Pin 1 thru pin 3= empty
Pin4= signal ground
Pin5= chassis ground
Pin6= ECM pin28 (2500) tan/blk canbus(+)
Pin7 thru pin13= empty
Pin14= ECM pin27 (2501) tan canbus(-)
Pin15= empty
Pin16= batt. (+) const. power
For me I used pin J5 from the “X4” connector (640) red/wht wire for pin 16.
I hope this will be a help to others and thank you all for the replies.
thank you Nick for your input..
PC GUY, I have not tested the ohm reading yet. I was focused on seeing if I could get the port to be read by the software, the software shows that I have a pedal code - I was told that I would get that first. I have not tried to fire it up yet... not quite ready yet. hoping in a couple of weeks. thank you again for your time.
pcguy, thank you for checking back in. I have the obdii port working & I finally broke down & bought a "cheap" code reader. I have read the codes (still not tried starting yet), but the port works fine. Now I have to figure out why I keep getting the P0223 code... the pedal is OG to the engine & all I have done is connect the ECM side of the pedal wires to the pedal pig tail inside the truck. anyways the port seems to be working for now. thank you again for your help & time spent.... if you are interested & fell like "wasting" a few minutes" Here is a link to my truck build: 67-72chevytrucks.com
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obd2 port not seeing ECM 
I am also trying to confirm my pin locations related to the "new" GMcanbus protocol (I believed started in 2010 ECMs??) 
. I am getting this info from diagrams & internet 
