GM Service Manual Online
For 1990-2009 cars only
Table 1: Fuse Block - Underhood (Primary) Label Usage
Table 2: Fuse Block - Underhood (Primary) Wire Entry
Table 3: Fuse Block - Underhood (Secondary) Label Usage
Table 4: Fuse Block - Underhood (Secondary) Wire Entry
Table 5: Fuse Block - I/P - 1 Label Usage
Table 6: Fuse Block - I/P - 1 Wire Entry
Table 7: Fuse Block - I/P - 2 Label Usage
Table 8: Fuse Block - I/P - 2 Wire Entry

Fuse Block - Underhood (Primary) Label


Object Number: 1556841  Size: LF

Fuse Block - Underhood (Primary) Label Usage

Device

Rating

Description

Important:: Numbers shown are to reference position only - component not marked.

NOTE 1 RELAY

--

LG4 Power Control Valve, L18/LB7 Fuel Pump, LG5 Heated Fuel

IGN B RELAY

--

Ignition

STARTER RELAY

--

Starter

HORN RELAY

--

Horn

IGN A RELAY

--

Ignition

PTO RELAY

--

Power Take-Off (PTO)

REVERSE RELAY

--

Reverse

NEUTRAL START RELAY

--

Neutral Start

RR DEFOG FUSE

30A

HVAC Control Assembly

ENG 1 FUSE

10A

PCV Relay (LG4) PTO Switch, Overdrive Defeat, Switch Rear Axle Actuator (LG5/L18/LB7)

ENG 3 FUSE

15A

Fuel Injectors (LG4) PTO Relay, Reverse Relay (L18/LG5) Intake Air Heater Relay (LG5) FICM (LB7)

PCM-B FUSE

10A

Serial Data Gateway, PCM (L18) ECM (All Others) TCM, ECM Relay (LG4)

BLANK FUSE

--

--

ENG 4 FUSE

15A

Cruise Control Switch

ENG 2 FUSE

10A

ECM, Heated Fuel Relay, Exhaust Relay, Fuel Injectors

HTD FUEL FUSE

20A

Heated Fuel Relay, Fuel Pump Relay

SPARE FUSE

--

--

SPARE FUSE

--

--

Fuse Block - Underhood (Primary) Top View


Object Number: 1556851  Size: LF

Fuse Block - Underhood (Primary) Bottom View


Object Number: 1556855  Size: LF

Fuse Block - Underhood (Primary) Wire Entry

Connector Part Information

    • 12146281
    • 86-Way Electrical Center (BK)

Pin

Wire Color

Circuit No.

Function

A1

PU

2675

Fuel Pump Relay Control - Primary (C8/LG5)

D-GN/ WH

465

Fuel Pump Relay Control - Primary (C8/LG5)

A3

OG

1640

Battery Positive Voltage (C8)

L-GN

260

Fuel Injection Control (LG4)

A4

RD

1042

Battery Positive Voltage (LB7)

PK

439

Ignition 1 Voltage (L18/ LG4/LG5)

A6

RD

1042

Battery Positive Voltage

A7

D-GN

1433

Clutch Start Switch Signal (LG5)

PU

806

Crank Voltage (L18/LG4/LB7)

A9

RD

242

Battery Positive Voltage

B1

OG

1540

Battery Positive Voltage (LG4)

GY

2677

Battery Positive Voltage (L18/LB7)

B2

--

--

Not Used

B3

BK

250

Ground

B4

PU

2000

Ignition 1 Voltage

B5

--

--

Not Used

B6

GY/BK

2219

FICM Relay Control

B7

PU

6

Starter Solenoid Crank Voltage (L18/LG4/LB7)

PU/WH

2667

Starter Solenoid Crank Voltage (LG5)

B8

--

--

Not Used

B9

YE

447

Starter Relay Coil Control

C1

OG

740

Battery Positive Voltage

C3

OG

740

Battery Positive Voltage

C4

PK

439

Ignition 1 Voltage

C6

RD

1042

Battery Positive Voltage

D1

D-GN

29

Horn Control

D2

--

--

Not Used

D3

BK

28

Horn Relay Control

D4

PU

2000

Ignition 1 Voltage

D5

--

--

Not Used

D6

BK

250

Ground

D7

PK

539

Ignition 1 Voltage (LG5)

L-GN

488

Ignition 1 Voltage (L18/LB7/LG4)

D9

PK

539

Ignition 1 Voltage (LG5)

WH

2561

Ignition 1 Voltage (L18/LB7/LG4)

E7

WH

2561

Ignition 1 Voltage (L18/LB7/LG4)

D-GN/WH

2665

Ignition 1 Voltage (LG5)

E8

--

--

Not Used

E9

L-GN

488

Ignition 1 Voltage (LG5)

PU

2562

Ignition 1 Voltage (L18/LB7/LG4)

F1

RD

2

Battery Positive Voltage

F3

PU

2000

Ignition Voltage Bus

F5

PU

2000

Ignition Voltage Bus

F7

RD

2

Battery Positive Voltage

F9

L-GN

24

Backup Lamp Supply Voltage

L-GN

24

Backup Lamp Supply Voltage

F11

GY

1524

Backup Lamp Supply Voltage/Backup Lamp Relay Control/Backup Lamp Signal

G2

PU

1093

Rear Defog Element Supply Voltage

G4

PK

239

Ignition 1 Voltage

G6

PK

539

Ignition 1 Voltage

G8

OG

440

Battery Positive Voltage

G10

--

--

Not Used

G12

--

--

Not Used

H1

--

--

Not Used

H3

PU

2000

Ignition Voltage

H5

PU

2000

Ignition Voltage

H7

RD

2

Battery Positive Voltage

H9

PK

539

Ignition 1 Voltage

H11

PK

139

Ignition 1 Voltage

J2

--

--

Not Used

J4

PK

639

Ignition 1 Voltage

J6

PK

339

Ignition 1 Voltage

J8

OG

1440

Battery Positive Voltage

J10

D-GN

1433

Clutch Start Switch Signal

J12

YE

1479

A/T Neutral Signal

K1

--

--

Not Used

K3

--

--

Not Used

K5

--

--

Not Used

K7

RD

2

Battery Positive Voltage Bus

K9-L2

--

--

Not Used

L4

OG

1240

Battery Positive Voltage

L6

OG

1240

Battery Positive Voltage

L8

OG

1240

Battery Positive Voltage

L10

BK

250

Ground

L12

PU

806

Crank Voltage

M1

RD

442

Battery Positive Voltage

M2

RD

1642

Battery Positive Voltage

M3

RD

42

Battery Positive Voltage

M4

RD

1042

Battery Positive Voltage

RD

1042

Battery Positive Voltage

M5

OG

1840

Battery Positive Voltage

M6

OG

740

Battery Positive Voltage

M7

OG

1640

Battery Positive Voltage

M8

--

--

Not Used

N1

--

--

Not Used

N2

--

--

Not Used

N3

--

--

Not Used

N4

--

--

Not Used

N5

--

--

Not Used

N6

--

--

Not Used

N7

--

--

Not Used

N8

--

--

Not Used

Fuse Block - Underhood (Secondary) Label


Object Number: 1556888  Size: SF

Fuse Block - Underhood (Secondary) Label Usage

No.

Device

Rating

Description

1

IGN 1 Fuse

50A

Ignition Switch, Transfer Case Shift Control Module (NP1)

2

IGN 4 Fuse

40A

Ignition 4 Relay

3

IGN 3 Fuse

50A

Ignition Switch

4

BAT/HAZ Fuse

60A

Fuse Block - I/P

5

HDLP Fuse

60A

Headlamp Switch, Fuse Block - I/P

6

LIGHTING Fuse

50A

Courtesy Fuse, Park Fuse

7

HVAC Fuse

40A

Blower Motor Resistor Assembly (C40/C60)

8

BRKLP Circuit Breaker

30A

Brake Lamps (C6/C7/C8)

ELEC BRK Circuit Breaker

Electronic Brake Control Module (EBCM) (C4/C5)

Fuse Block - Underhood (Secondary) Top View


Object Number: 1556879  Size: LF

Fuse Block - Underhood (Secondary) Bottom View


Object Number: 1556880  Size: LF

Fuse Block - Underhood (Secondary) Wire Entry

Connector Part Information

    • 12092231
    • 16-Way Fuse Block Component (BK)

Pin

Wire Color

Circuit No.

Function

A1

RD

242

Battery Positive Voltage

A2

RD

1242

Battery Positive Voltage

A3

RD

342

Battery Positive Voltage

A4

RD

142

Battery Positive Voltage

A5

RD

1142

Battery Positive Voltage

A6

RD

1342

Battery Positive Voltage

A7

RD

542

Battery Positive Voltage

A8

RD

642

Battery Positive Voltage

B1

--

1

Battery Positive Voltage Bus

B2

--

1

Battery Positive Voltage Bus

B3

--

1

Battery Positive Voltage Bus

B4

--

1

Battery Positive Voltage Bus

B5

--

1

Battery Positive Voltage Bus

B6

--

1

Battery Positive Voltage Bus

B7

--

1

Battery Positive Voltage Bus

B8

--

1

Battery Positive Voltage Bus

Fuse Block - I/P - 1 Label


Object Number: 1556860  Size: LF

Fuse Block - I/P - 1 Label Usage

Fuse No.

Device

Rating

Description

1

STOP

20A

Stop Lamp Switch, Trailer Stop Lamp Switch

2

CHMSL

20A

CHMSL Relay

3

PARK

20A

Headlamp Switch

4

PCM - 1

15A

EBCM, PCM, ECM, TAC

5

AUX RLY

15

Battery ISO, DRL Module, Outside Heated Mirror Switch, Heated Mirror Relay

6

HTR/AC

20A

Air Temp Actuator, Vacuum Pump, HVAC Control Assembly, Blower Motor Relay-Aux

7

HAZARD

25A

Turn Signal/Multifunction Switch

8

PWR ST

20A

Cigar Lighter, Diagnostic Tool Connector, Aux Power 1, 2 DLC

9

COURTESY

10A

Dome Lamps

10

GAUGES

10A

(RCDLR) Headlamp Switch, DRL Relay, Instrument Panel Gage Cluster, DIC, IPC

11

START

10A

Starter Relay, Clutch Start Switch, PNP Switch, Neutral Start Relay, EBCM

12

AXLE/4WD

20A

Rear Axle Shift Relay-Two Speed

13

TRLR TRN/HAZ

20A

Left Turn Trailer Relay, Right Turn Trailer Relay

14

RADIO/CHIME

20A

Radio, Chime Module, IPC

15

DRL

15A

Daytime Running Lamps Diode

16

SIR

10A

Inflatable Restraint I/P Module Switch (Pickup Only), and Inflatable Restraint Sensing and Diagnostic Module (SDM)

17

ILLUM

10A

IPC, HVAC Control Assembly, Inflatable Restraint Disable Switch, Radio, Transfer Case Shift Control Switch

18

BRAKE

10A

A/C Compressor Clutch Relay, High Idle Switch, Clutch Pedal Position, Air Brake Relay, Stop Lamp Switch

19

PWR/ACCY

20A

Blower Motor Relay-Aux, Outside Rearview Mirror, Door Lock Switch, Remote Control Door Lock Receiver

20

IGN 4

25A

IGN 4 Relay, IPC, Windshield Wiper Motor, Turn Signal Multifunction Switch

21

MARKER LAMP

20A

Marker Lamp Relay

22

TURN/BACKUP

20

Reverse Relay, PNP Switch, Backup Lamp Switch, Turn Signal/Multifunction Switch

23

TRANS

15A

SDG, IPC, TCM, ECM

24

CHASSIS

15

Low Air Pressure Switch, Air Brake Dryer, Traction Control Switch, Air Suspension Dump Switch

A

SPARE

--

--

B

SPARE

--

--

Fuse Block - I/P - 1 Front View


Object Number: 1556863  Size: LF

Fuse Block - I/P - 1 Back View


Object Number: 1556866  Size: LF

Fuse Block - I/P - 1 Wire Entry

Connector Part Information

    • 12110746
    • 48-Way Metri-Pack 280 Series (BK)

Pin

Wire Color

Circuit No.

Function

A2

--

--

Not Used

A3

--

--

Not Used

A6

--

--

Not Used

A7

--

--

Not Used

B2

--

--

Not Used

B4

RD

142

Battery Positive Voltage

B6

--

--

Not Used

B8

--

--

Not Used

C1

OG

540

Battery Positive Voltage

C3

OG

640

Battery Positive Voltage Inadvertent Power Relay Enable

C5

OG

1040

Battery Positive Voltage

C7

OG

140

Battery Positive Voltage

D2

BN

4

Accessory Voltage

D4

--

--

Not Used

D6

RD

142

Battery Positive Voltage

D8

--

--

Not Used

E1

YE

43

Accessory Voltage

E3

OG

1140

Battery Positive Voltage

E5

OG

840

Battery Positive Voltage

E7

OG

1740

Battery Positive Voltage

F2

--

--

Not Used

F4

RD

1142

Battery Positive Voltage

F6

--

--

Not Used

F8

RD

1342

Battery Positive Voltage

G1

OG

1340

Battery Positive Voltage

G3

OG

340

Battery Positive Voltage

G5

OG

40

Battery Positive Voltage

G7

OG

240

Battery Positive Voltage

H2

--

--

Not Used

H4

PK

3

Ignition 1 Voltage

H6

--

--

Not Used

H8

--

--

Not Used

J1

PK

139

Ignition 1 Voltage

J3

YE

1139

Ignition 1 Voltage

J5

PK

39

Ignition 1 Voltage

J7

PK

439

Ignition 1 Voltage

K2

WH

1390

Off Run Crank Voltage

K4

D-GN

44

Instrument Panel Lamps Dimmer Switch Signal

K6

YE

5

Crank Voltage

K8

OG

300

Ignition 3 Voltage

L1

PK

1020

Off Run Crank Voltage

L3

GY

8

Instrument Panel Lamp Supply Voltage 1

L5

PU

806

Crank Voltage

L7

BN

641

Ignition 3 Voltage

M2

--

--

Not Used

M4

OG

300

Ignition 3 Voltage

M6

--

--

Not Used

M8

--

--

Not Used

N1

BN

541

Ignition 3 Voltage

N3

BN

441

Ignition 3 Voltage

N5

--

--

Not Used

N7

BN

141

Ignition 3 Voltage

Fuse Block - I/P - 2 Label


Object Number: 1556869  Size: SF

Fuse Block - I/P - 2 Label Usage

Device

Rating

Description

Important: Numbers shown are to reference position only - component not marked.

RT PARK FUSE

10A

Right-Hand Parking Lamps

LT PARK FUSE

10A

Left-Hand Parking Lamps

RADIO FUSE

10A

Radio

PWR WDO FUSE

25A

Power Windows

BRAKE ISO FUSE

10A

Brake Warning Lamp

SPARE FUSE

--

SPARE FUSE

L-RR TRUCK FUSE

15A

Front Axle Actuator, Transfer Case Shift Control Switch, Auxiliary Battery Relay

SPARE FUSE

--

Spare Fuse

SPARE FUSE

--

Spare Fuse

SPARE FUSE

--

Spare Fuse

R-RR TRUCK FUSE

15A

Right Rear Trailer Wiring

SPARE FUSE

--

Spare Fuse

BRAKE LAMP RELAY

--

C4/C5 Brake Lamps, C6/C7/C8 Tractor/Trailer Wiring

IGN 4 RELAY

--

Ignition

MARKER LP RELAY

--

Side Marker and Clearance Lamps

HTD FUEL RELAY

--

LB7/LG4 Heater

AIR HTR RELAY

--

LG4 Air Heater

ECU MAINTAIN RELAY

--

LG4 Electronic Control Unit

DRL RELAY

--

Daytime Running Lamps

CHMSL ISO RELAY

--

Center High Mounted Stop Lamp

HTD MIR RELAY

--

Heated Mirror

R-TRN TLR RELAY

--

Right Trailer Turn Signal

L-TRN TLR RELAY

--

Left Trailer Turn Signal

SPARE RELAY

--

Spare Relay

SPARE RELAY

--

Spare Relay

SPARE RELAY

--

Spare Relay

Fuse Block - I/P - 2 Front View


Object Number: 1556872  Size: MF

Fuse Block - I/P - 2 Back View


Object Number: 1556877  Size: MF

Fuse Block - I/P - 2 Wire Entry

Connector Part Information

    • 12129833
    • 94-Way F Fuse Block (BK)

Pin

Wire Color

Circuit No.

Function

A30

--

--

Not Used

A85

--

--

Not Used

A87A

--

--

Not Used

A87

--

--

Not Used

A86

--

--

Not Used

B30

--

--

Not Used

B85

--

--

Not Used

B87A

--

--

Not Used

B87

--

--

Not Used

B86

--

--

Not Used

C30

--

--

Not Used

C85

--

--

Not Used

C87A

--

--

Not Used

C87

--

--

Not Used

C86

--

--

Not Used

D30

YE

318

Left Rear Trailer Stop Turn Lamp Supply Voltage

D85

YE

618

Left Rear Turn Signal Lamp Supply Voltage

L-BU

14

Left Turn Signal Status Signal

D87A

--

--

Not Used

D86

BK

450

Ground

D87

OG

640

Battery Positive Voltage Inadvertent Power Relay Enable

E30

D-GN

319

Right Rear Trailer Stop Turn Lamp Supply Voltage

E85

D-GN

619

Right Rear Turn Signal Lamp Supply Voltage (FAM 2)

E87A

D-GN

15

Right Turn Signal Status Signal (FAM 3)

E86

BK

450

Ground

E87

OG

640

Battery Positive Voltage Inadvertent Power Relay Enable

F30

OG

267

Heated Mirror Rear Defog Relay Coil Supply Voltage

F85

BK

450

Ground

F86

OG

267

Heated Mirror Rear Defog Relay Coil Supply Voltage

F87A

--

--

Not Used

F87

BN

641

Ignition 3 Voltage

G30

OG

1740

Battery Positive Voltage

G85

BK

450

Ground

G87A

--

--

Not Used

G86

L-BU

1320

CHMSL Supply Voltage Stop Lamp Supply Voltage

G87

YE

895

Left Rear Stop Lamp Supply Voltage

H30

TN

12

Headlamp Low Beam Supply Voltage

H85

L-GN/BK

592

DRL Relay Control

H86

PK

39

Ignition 1 Voltage

H87

YE

634

DRL Diode Supply Voltage

H87A

PU

544

Headlamp Low Beam Supply Voltage

J30

BK/WH

1120

ECM Power

J85

OG

440

Battery Positive Voltage

J87A

--

--

Not Used

J86

L-BU

1121

ECM Power Enable

J87

OG

440

Battery Positive Voltage

K30

RD

1411

Trailer Stop Relay - Contact - N.O.

K85

L-BU

1320

CHMSL Supply Voltage Stop Lamp Supply Voltage

K86

BK

450

Ground

K87A

--

--

Not Used

K87

RD

1542

Battery Positive Voltage

L30

BK

755

RAP Relay Coil Control

L85

YE

43

Accessory Voltage

L87A

--

--

Not Used

L86

BK

450

Ground

L87

RD

1242

Battery Positive Voltage

M30

OG

1340

Battery Positive Voltage

M85

OG/BK

2666

Ignition 1 Voltage

M87A

--

--

Not Used

M86

BN/WH

2609

Right Rear Park Lamps Supply Voltage

M87

D-GN

21

Roof Clearance Lamp Switch Signal

N30

PK

2677

Battery Positive Voltage

N85

PK

339

Ignition 1 Voltage

N87A

--

--

Not Used

N86

BK

450

Ground

N87

OG

1440

Battery Positive Voltage

P30

GY

5481

Ground

P85

BK/WH

1120

Ground

P87A

--

--

Not Used

P86

BN

5347

Ground

P87

BK/WH

1120

Ground

R1

RD

9

Park Lamp Supply Voltage Bus

R2

YE

343

Accessory Voltage

R3

BN

9

Park Lamp Supply Voltage

R4

OG

2040

Battery Positive Voltage

R5

RD

9

Park Lamp Supply Voltage Bus

R6

BN

2509

Left Rear Park Lamps Supply Voltage Left Rear Park Lamps and License Lamps Supply Voltage

R7

--

--

Not Used

R8

BN/WH

2609

Right Rear Park Lamps Supply Voltage

S1-S2

--

--

Not Used

S3

YE

18

Left Rear Stop Turn Lamp Supply Voltage

S4

YE

618

Left Rear Turn Signal Lamp Supply Voltage

S5-S6

--

--

Not Used

S7

WH

17

Stop Lamp Switch Signal

S8

L-BU

1320

CHMSL Supply Voltage Stop Lamp Supply Voltage

T1-T2

--

--

Not Used

T3

D-GN

19

Right Rear Stop Turn Lamp Supply Voltage

T4

D-GN

619

Right Rear Turn Signal Lamp Supply Voltage

T5-T7

--

--

Not Used

T9-T7

--

--

Not Used