Powertrain Controls - ECM/PCM

DTC 37:

Brake Switch Circuit.:

CIRCUIT DESCRIPTION
The Torque Converter Clutch (TCC) brake switch is used to indicate brake pedal status. The normally closed brake switch supplies a B+ signal on CKT 420 to the Powertrain Control Module (PCM). The signal voltage is opened when the brakes are applied. The PCM uses this signal to de-energize the TCC solenoid when the brakes are applied.


DTC 37 WILL SET WHEN:
CKT 420 is open AND,
- Vehicle speed is less than 5 mph.
- Then vehicle speed is between 5 mph.
- Then vehicle speed is greater than 30 mph for greater than 6 seconds.
- For a complete total of seven times.

ACTION TAKEN (PCM will default to):
An incorrect brake signal can affect TCC scheduling. Also, an incorrect brake signal can inhibit fourth gear operation, if in hot mode. DTC 37 will be stored in PCM memory, but, will not turn "ON" the Malfunction Indicator Lamp (MIL).

DTC 37 WILL CLEAR WHEN:
Fault condition no longer exists.

DTC CHART 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 checks the brake switch.
3. This test checks CKT 420 at the PCM.

DIAGNOSTIC AIDS
Check customer driving habits and/or unusual traffic conditions (i.e. stop and go expressway traffic).