Fig 1: Connector End View

Courtesy of GENERAL MOTORS CORP.

Connector Part Information

OEM: 34566-9403
Service: 88988372
Description: 73-Way F MX123 Series (BK)

Terminal Part Information

Pins: 73
Terminal/Tray: See Terminal Repair Kit
Core/Insulation Crimp: See Terminal Repair Kit
Release Tool/Test Probe: See Terminal Repair Kit

Pins: 4-8, 10, 16, 20, 30, 32, 33, 35, 37, 38, 41, 45, 46, 48, 50, 51, 54, 58, 65, 66, 67, 68
Terminal/Tray: 33467-0005/23
Core/Insulation Crimp: J/J
Release Tool/Test Probe: J-38125-213/J-35616-64B (L-BU)

Pins: 9, 13, 22-24, 26, 31, 39, 40, 42, 43, 49, 53, 57, 59
Terminal/Tray: 33467-0003/23
Core/Insulation Crimp: H/H
Release Tool/Test Probe: J-38125-213/J-35616-64B (L-BU)

Connector Terminal Identification

Pin	Wire Color	Circuit No.	Function
1-3	-	-	Not Used
4	TN	2761	Low Reference
5	PU	574	Low Reference
6	TN	1744	Fuel Injector (1) Control
7	PK/BK	1746	Fuel Injector (3) Control
8	L-BU/BK	844	Fuel Injector (4) Control
9	BN	2129	Low Reference
10	L-GN/BK	1745	Fuel Injector (2) Control
11-12	-	-	Not Used
13	GY/BK	2704	5-Volt Reference
14-15	-	-	Not Used
16	YE	581	TAC Motor Control (1)
17-19	-	-	Not Used
20	TN	5301	Low Reference
21	-	-	Not Used
22	PU	2121	Ignition Control (1)
23	L-BU	2123	Ignition Control (3)
24	D-GN/WH	2124	Ignition Control (4)
25	-	-	Not Used
26	OG/WH	2122	Ignition Control (2)
27-29	-	-	Not Used
30	D-GN/WH	428	EVAP Canister Purge Solenoid Control
31	OG	225	Generator Turn On Signal
32	BN	582	TAC Motor Control (2)
33	D-BU	5300	5-Volt Reference
34	-	-	Not Used
35	GY	6255	5-Volt Reference
36	-	-	Not Used
37	PU/WH	3110	Heated Oxygen Sensor High Signal Sensor 1
38	PU/WH	1668	Heated Oxygen Sensor High Signal Sensor 2
39	L-GN	432	Manifold Absolute Pressure Sensor Signal
40	TN	2752	Low Reference
41	PU/WH	6256	Low Reference
42	TN	2760	Low Reference
43	GY/WH	23	Generator Field Duty Cycle Signal
44	-	-	Not Used
45	YE	573	Crankshaft Position Sensor Signal
46	OG	5275	CMP Sensor Signal
47	-	-	Not Used
48	TN/WH	3111	Heated Oxygen Sensor Low Signal Sensor 1
49	OG/BK	469	Low Reference
50	GY	1716	Knock Sensor Signal
51	D-BU	496	Knock Sensor Signal
52	-	-	Not Used
53	GY	2701	5-Volt Reference
54	L-GN	2867	5-Volt Reference
55-56	-	-	Not Used
57	D-GN	485	Throttle Position Sensor (1) Signal
58	YE	410	Engine Coolant Temperature Sensor Signal
59	PU	486	Throttle Position Sensor (2) Signal
60-64	-	-	Not Used
65	GY/WH	3113	Heated Oxygen Sensor Heater Low Control Sensor 1
66	GY/WH	1423	Heated Oxygen Sensor Heater Low Control Sensor 2
67	TN/BK	231	Oil Pressure Switch Signal
68	TN/WH	1669	Heated Oxygen Sensor Low Signal Sensor 2
69-72	-	-	Not Used
73	BK/WH	451	Signal Ground

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.

Safety Warning

Engine Control Module (ECM) Connector End View C2

Use the Manual With the Right Hardware

When to See a Mechanic