2006 Cadillac STS VFACTORY OEM SERVICE PROCEDURE

Engine Control Module (ECM) C3

Fig 1: ECM C3 Connector
GM1650395Courtesy of GENERAL MOTORS CORP.
Engine Control Module Connector End Views

Connector Part Information 
  • OEM: 34566-3303
  • Service: 88988372
  • Description: 73-Way F (GY)
Terminal Part Information 
  • Pins: 73
  • Terminal/Tray: 7116-4152-02/9
  • Core/Insulation Crimp: 2/5
  • Release Tool/Test Probe: 12094430/J-35616-35 (VT)
  • Pins: 3, 4, 5, 6, 7, 14, 15, 16, 18, 21, 22, 23, 29, 33, 34, 35, 37, 38, 39, 46, 50, 53, 55, 56, 57, 58, 59
  • Terminal/Tray: 33467-0005/23
  • Core/Insulation Crimp: J/J
  • Release Tool/Test Probe: J-38125-213/J-35616-64B (L-BU)
  • Pins: 48, 49
  • Terminal/Tray: 33467-0003/23
  • Core/Insulation Crimp: H/H
  • Release Tool/Test Probe: J-38125-213/J-35616-64B (L-BU)
Engine Control Module (ECM) C3

Pin Wire Color Circuit No. Function
1-2 - - Not Used
3 TN/WH 3211 HO2S Low Reference (Bank 2 Sensor 1)
4 PU/WH 3210 HO2S Reference Voltage (Bank 2 Sensor 1)
5 PU 3220 HO2S High Signal (Bank 2 Sensor 2)
6 TN 3221 HO2S Low Signal (Bank 2 Sensor 2)
7 OG 225 Generator Turn On Signal
8-13 - - Not Used
14 L-BU 7126 Super Charger Vacuum Bypass Valve Control
15 L-GN 3212 HO2S Heater Low Control (Bank 2 Sensor 1)
16 PK 2014 Coolant Pump Relay Control
17 - - Not Used
18 BN 1174 Oil Level Switch Signal
19-20 - - Not Used
21 BK/WH 2751 Low Reference
22 OG/BK 6014 BARO Sensor Low Reference
23 OG/BK 469 Low Reference
24-28 - - Not Used
29 GY 23 Generator Field Duty Cycle Signal
30-32 - - Not Used
33 TN 2501 High Speed GMLAN Serial Data Bus -
34 YE/BK 6120 IAT2 Low Reference
35 TN 2761 Low Reference
36 - - Not Used
37 GY 2700 5-Volt Reference
38 WH/BK 2932 5-Volt Reference
39 GY 2704 5-Volt Reference
40-45 - - Not Used
46 OG/BK 1786 Park/Neutral Signal
47 - - Not Used
48 PU 428 EVAP Canister Purge Solenoid Control
49 D-GN 335 Low Speed Cooling Fan Relay Control
50 OG/BK 3223 HO2S Heater Low Control (Bank 2 Sensor 2)
51-52 - - Not Used
53 TN-BK 2500 High Speed GMLAN Serial Data Bus +
54 - - Not Used
55 YE 410 ECT Sensor Signal
56 L-BU 6118 IAT2 Signal
57 OG/BK 380 A/C Refrigerant Pressure Sensor Signal
58 GY-BK 433 BARO Sensor Signal
59 L-GN 432 MAP Sensor Signal
60-72 - - Not Used
73 BK/WH 1551 Ground
Factory Service Tools

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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.