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 MANUALSCHEVROLET1993SUBURBAN 3/4 TON 2WD V8-454 7.4LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSBRAKE SIGNALTESTING AND INSPECTION
1993 Chevrolet Suburban 3/4 Ton 2WD V8-454 7.4L
Brake Signal: Testing and Inspection
1993 Chevrolet Suburban 3/4 Ton 2WD V8-454 7.4LSECTION Testing and Inspection
Brake Signal Circuit Check:
Brake Signal Circuit:
CIRCUIT DESCRIPTION:
The normally closed brake switch supplies a 12 volts signal on CKT 420 to the PCM/TCM. The signal voltage is opened when the brakes are applied. An inc9rrect brake signal can affect TCC operation.
TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test checks for voltage at brake switch.
2. This test simulates brake switch closed or brakes OFF."
3. This test checks CKT 420 from brake switch to PCM/TCM.
4. This test opens CKT 420 and simulates brakes being applied.
DIAGNOSTIC AIDS:
^ Refer to "PCM/TCM Intermittent DTC(s) or Performance."
^ Check customer driving habits and/or unusual traffic conditions (i.e. stop and go expressway traffic).
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.