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 MANUALSCHEVROLET1993ASTRO VAN L AWD V6-262 4.3L VIN W CPIREPAIR AND DIAGNOSISA L L DIAGNOSTIC TROUBLE CODES ( DTC )TESTING AND INSPECTIONMANUFACTURER CODE CHARTSDTC 37POWERTRAIN CONTROLS - ECM/PCM
1993 Chevrolet Astro Van L AWD V6-262 4.3L VIN W CPI
Powertrain Controls - ECM/PCM
1993 Chevrolet Astro Van L AWD V6-262 4.3L VIN W CPISECTION Powertrain Controls - ECM/PCM
DTC 37 Brake Switch Stuck "ON":
Brake Signal Circuit:
Circuit Description:
The normally closed brake switch supplies a 12 volt signal on CKT 420 to the PCM. The signal voltage is opened when the brakes are applied. An incorrect brake signal can affect TCC and fourth gear operation, in hot mode.
DTC 37 will set when CKT 420 is open, vehicle speed below 5 mph for 6 seconds, then between 5 mph and 20 mph for 6 seconds, then greater than 20 mph for 6 seconds, for a complete total of seven times.
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.
4. This test opens CKT 420 and simulates brakes being applied.
Diagnostic Aids:
^ Refer to "Diagnosis By Symptom."Testing and Inspection
^ 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.