Powertrain Controls - ECM/PCM

DTC 37 Chart:

Torque Converter Clutch Brake Switch Circuit:

Circuit Description:
The TCC brake switch is used to indicate brake pedal status. The normally closed brake switch supplies a B+ signal on CKT 420 to the PCM. The signal voltage is opened when the brakes are applied. The PCM uses this signal to de-energize the TCC solenoid when the brake pedal is applied.

DTC 37 Will Set When:
- No DTC(s) 24 or 72.
- No change in the TCC brake signal to the PCM when:

- Vehicle speed is greater than 35 mph for greater than 10 seconds.
- Then vehicle speed is 0 mph.
- For a total of 4 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.

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).