Powertrain Controls - ECM/PCM

Chart DTC 37 TCC Brake:

Circuit DTC 37 TCC Brake:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) monitors brake pedal activity through PCM terminal "A18". The Stoplamp / Torque Converter Clutch (TCC) / Cruise Control switch is a normally closed switch that opens to interrupt system voltage to the PCM input when the brake pedal is applied.

Diagnostic Trouble Code (DTC) 37 Will Set When: Vehicle speed is maintained above 35 mph for 10 seconds and back to 0 mph for 4 consecutive times without the PCM sensing a voltage change on CKT 420 (displayed "RELEASED" to "APPLIED" on Scan tool).

Action Taken (PCM will default to): The PCM will not illuminate the Malfunction Indicator Lamp (MIL). If the switch has failed in an open state, the TCC will not engage.

DTC 37 Will Clear When: A current DTC 37 will clear when the PCM begins detecting "APPLIED" to "RELEASED" transitions. A History DTC 37 will clear after 50 consecutive ignition key cycles without a current DTC 37 being stored.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This test checks for voltage at Stoplamp / TCC / Cruise Control switch.
2. This test simulates Stoplamp / TCC / Cruise Control switch closed or brakes "OFF."
3. This test checks CKT 420 from Stoplamp / TCC / Cruise Control switch to PCM.
4. This test opens CKT 420 and simulates brakes being applied.

DIAGNOSTIC AIDS
A DTC 37 can be caused by a misadjusted brake switch or a poor connection.

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