2008 Hummer H3 Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Engine Control Module (ECM) X1

Fig 1: Engine Control Module (ECM) X1 Connector End View
GM1590948Courtesy of GENERAL MOTORS CORP.
Engine Control Module (ECM) X1

Pin Wire Circuit Function
1 - - Not Available
2 0.35 PU 420 Cruise Control Release Signal
3 - - Not Available
4 0.35 GY/BK 1694 4WD Low Signal
5-6 - - Not Available
7 0.5 L-BU 20 Stop Lamp Control
8 - - Not Available
9 0.35 BK 2759 Low Reference
10-11 - - Not Available
12 0.35 BN/WH 419 MIL Control
13 0.35 D-GN/WH 465 Fuel Pump Relay Control
14 - - Not Available
15 0.35 PU 1807 Class 2 Serial Data
16 0.35 PU 1807 Class 2 Serial Data
17 - - Not Available
18 0.5 BN 4 Ignition Voltage
19 0.35 PK 639 Ignition Voltage
20 0.35 OG 440 Battery Positive Voltage
21-25 - - Not Available
26 0.35 YE/BK 625 Starter Enable Relay Control
27-28 - - Not Available
29 0.35 GY 1884 Cruise Control Switch Signal
30-32 - - Not Available
33 0.35 WH/BK 1164 5-Volt Reference 2
34 0.35 GY 2709 5-Volt Reference 1
35 0.35 TN 1274 5-Volt Reference 1
36 0.35 BN 1271 Low Reference
37 0.35 PU 1272 Low Reference
38 - - Not Available
39 0.35 D-GN/WH 817 Vehicle Speed Signal
40 0.35 WH/BK 5991 Powertrain Relay Control
41-43 - - Not Available
44 0.35 PU 1589 Fuel Level Sensor Signal
45-46 - - Not Available
47 0.35 D-BU 1161 APP Sensor 1 Signal
48 0.35 D-GN 890 Fuel Tank Pressure Sensor Signal
49 0.35 L-BU 1162 APP Sensor 2 Signal
50 - - Not Available
51 0.35 PU 421 AIR Solenoid Relay Control
52 - - Not Available
53 0.35 D-GN/WH 459 A/C Compressor Clutch Relay Control
54 - - Not Available
55 0.5 WH 1310 EVAP Canister Vent Solenoid Control
56-73 - - Not Available
Connector Part Information 
  • OEM: 12582680
  • Service: 88988373
  • Description: 56-Way F MX123 Series, Sealed (BU)
Terminal Part Information 
  • Terminal/Tray: See Terminal Repair Kit
  • Core/Insulation Crimp: Terminal Repair Kit
  • Release Tool/Test Probe: Terminal Repair Kit
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.