Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSBUICK1991CENTURY L4-151 2.5L VIN R TBIREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTDIAGRAMSELECTRICAL DIAGRAMSELECTRONIC/POWERTRAIN CONTROL MODULE (ECM/PCM)
1991 Buick Century L4-151 2.5L VIN R TBI
Electronic/Powertrain Control Module (ECM/PCM)
1991 Buick Century L4-151 2.5L VIN R TBISECTION Electronic/Powertrain Control Module (ECM/PCM)
ECM Wiring Diagram (1 Of 3):
B1 = SERIAL DATA
B15 = DIAGNOSTIC TEST
W12 = ECM GROUND
W13 = ECM GROUND
B23 = OXYGEN SENSOR GROUND
B2 = OXYGEN SENSOR SIGNAL
B13 = VSS INPUT (HIGH)
B6 = VSS INPUT (LOW)
W22 = VSS OUTPUT
B8 = COOLANT TEMPERATURE SIGNAL
B12 = SENSOR GROUND
B19 = TPS SIGNAL
W11 = 5 VOLT REFERENCE
B20 = MAP SIGNAL
W14 = SENSOR GROUND
B5 = IAT SIGNAL
W7 = IAC COIL "A" HIGH
W17 = IAC COIL "A" LOW
W9 = IAC COIL "B" HIGH
W8 = IAC COIL "B" LOW
ECM Wiring Diagram (2 Of 3):
W18 = PARK NEUTRAL SWITCH (A/T)
W5 = POWER STEERING PRESSURE SIGNAL
B22 = SERVICE ENGINE SOON LIGHT CONTROL
B7 = TCC CONTROL
B18 = COOLANT TEMPERATURE LIGHT CONTROL
W16 = IGNITION
W1 = INJECTOR DRIVER
B16 = GROUND
B9 = REFERENCE
W19 = BYPASS
W6 = EST
ECM Wiring Diagram (3 Of 3):
W10 = BATTERY +
W15 = BATTERY +
W24 = FUEL PUMP RELAY DRIVE (12V)
W12 = ECM GROUND
W13 = ECM GROUND
B24 = A/C FAN SIGNAL
W2 = A/C REQUEST
B3 = A/C RELAY CONTROL
B21 = COOLING FAN CONTROL
RENDER: 1.0x
NO RELATED
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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.