Powertrain Controls - ECM/PCM

DTC 38 Brake Switch Stuck "OFF":

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.
DTC 38 will set when CKT 420 has voltage, vehicle speed is greater than 20 mph for 6 seconds, then between 5 mph and 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).