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 MANUALSCHEVROLET1990BLAZER FULL SIZE V8-350 5.7LREPAIR AND DIAGNOSISDIAGRAMSELECTRICAL DIAGRAMSPOWERTRAIN MANAGEMENTSYSTEM DIAGRAMELECTRONIC/POWERTRAIN CONTROL MODULE (ECM/PCM)
1990 Chevrolet Blazer Full Size V8-350 5.7L
Electronic/Powertrain Control Module (ECM/PCM)
1990 Chevrolet Blazer Full Size V8-350 5.7LSECTION Electronic/Powertrain Control Module (ECM/PCM)
ECM Wiring Diagram (Part 1 Of 6):
A8 = SERIAL DATA.
A9 = DIAGNOSTIC TEST.
A12 = SYSTEM GROUND.
D1 = SYSTEM GROUND.
C9 = CRANK SIGNAL.
D7 = OXYGEN SENSOR SIGNAL.
D6 = OXYGEN SENSOR GROUND.
D2 = MAP GROUND (4.3L & V8 EXCEPT C/K).
A11 = MAP GROUND (4.3L & V8 C/K).
C14 = +5V REFERENCE.
C13 = TPS SIGNAL.
A11 = SENSOR GROUND (4.3L & V8 C/K).
D2 = SENSOR GROUND (4.3L & V8 EXCEPT C/K).
C10 = COOLANT TEMPERATURE SENSOR.
C5 = IAC COIL "A" HI.
C6 = IAC COIL "A" LO.
C4 = IAC COIL "B" HI.
C3 = IAC COIL "B" LO.
ECM Wiring Diagram (Part 2 Of 6):
B8 = A/C SIGNAL.
B8 = A/C CLUTCH SIGNAL.
A2 = CLUTCH CONTROL.
B1 = 12 VOLTS.
C16 = 12 VOLTS.
A1 = FUEL PUMP RELAY DRIVE (12V).
B2 = FUEL PUMP SIGNAL.
ECM Wiring Diagram (Part 3 Of 6):
B1 = 12 VOLTS.
C16 = 12 VOLTS.
B2 = FUEL PUMP SIGNAL.
B1 = 12 VOLTS.
C16 = 12 VOLTS.
A1 = FUEL PUMP RELAY DRIVE (12V).
B2 = FUEL PUMP SIGNAL.
ECM Wiring Diagram (Part 4 Of 6):
B1 = 12 VOLTS.
C16 = 12 VOLTS.
A1 = FUEL PUMP RELAY DRIVE (12V).
B2 = FUEL PUMP SIGNAL.
A5 = SERVICE ENGINE SOON LIGHT CONTROL.
C7 = HIGH GEAR SWITCH SIGNAL.
A7 = A/T TCC CONTROL GROUND.
A7 = A/T DOWNSHIFT CONTROL (GROUND).
ECM Wiring Diagram (Part 5 Of 6):
A7 = A/T DOWNSHIFT CONTROL (GROUND).
A7 = M/T SHIFT LAMP (GROUND EXCEPT R/V,P).
A10 = VEHICLE SPEED SENSOR SIGNAL.
B10 = PARK NEUTRAL SWITCH (A/T)(12V)(EXCEPT P).
A4 = EGR SOLENOID.
A4 = EVRV SOLENOID.
C2 = EAC SOLENOID.
A6 = 12 VOLT IGNITION.
B7 = KNOCK RETARD SIGNAL (ESC).
ECM Wiring Diagram (Part 6 Of 6):
D16 = INJECTOR DRIVER.
D15 = INJECTOR DRIVER.
D14 = INJECTOR DRIVER.
C15 = INJECTOR DRIVER.
D16 = INJECTOR DRIVER.
D14 = INJECTOR DRIVER.
D4 = EST.
B5 = REFERENCE.
D5 = BYPASS.
B3 = REFLOW.
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.