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I have a 6.0L I pulled from a 2003 Escalade to swap into my Jeep. I sent the harness and computer to 150 tunes to trim the harness and tune the computer. The motor runs fine, but I have a CEL and want to check codes in addition to getting live data. However, I cannot get my scanner to connect to the ECU.

Here is what I have tried and checked.
  • 4 different scanners, all verified to work on other vehicles, but none will connect to my ECU.
  • All scanners power up.
  • I have no coins in my cigarette lighter port.
  • I have power to pin 16, pins 4&5 are both ground, and OBD2 pin2 is wired to the ECU pin58 on the blue connector.
  • I have tried unplugging individual sensors one at a time and all of them at once.
  • The guy who tuned it has been more defensive than helpful.
  • ECU Pin 59 (class two serial data) on the blue connector was cut and incorrectly labeled as the fan relay ground by the tuner/harness guy. I have since re-pinned it to Blue 42 and believe I have the fan relay ground working.

  1. What OBD2 protocol does a 2003 Escalade use?
  2. What wires go to a unmolested OBD2 port for these vehicles?
  3. Where does the wire on Pin 59 of the blue ECU connector go? (Class two serial data as per
  4. If anyone had a FSM, specifically wring diagrams, that would be very helpful.

'05 Escallade ESV Plat., '16 Z51 Corvette, '03 Avalanche, 12 Lexus IS350C
158 Posts
I'm curious how much response you will get here.
Not many people really get into the inner workings of their Escalade.
I would be checking out LS1TECH. They have a pretty extensive forum.
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