Part 1 of 2

DTC P039:

Brake Switch Circuit:

CIRCUIT DESCRIPTION:
The torque converter clutch solenoid controls the hydraulic fluid for TCC apply or release. The diagnostic test checks for a torque converter clutch not engaged or slipping condition by monitoring the slip speed. Slip speed is the difference between engine speed and transaxle turbine speed. When the TCC is applied, the engine is coupled directly to the transaxle through the TCC. Almost no slippage should occur, so the slip speed is nearly 0. If RPM is too high at a given speed, the PCM diagnosis the condition as the TCC slipping or not engaged and Code P039 is set.

TEST CONDITION(S):
1. Codes P024, P026, P027, P028, P031, P032, P034, P056 and P075 not set.
2. Transaxle in 3rd or 4th gear.
3. Engine running.
4. TCC commanded "ON" (100%).
5. Transaxle not in park or neutral.
6. Throttle position switch open.
7. Delivered torque from engine not 20 lb. ft. or less (coast down condition).
8. Delivered torque from engine not 508 lb. ft. or more (engine under extreme load (Example: towing a trailer or wide open throttle).

FAILURE CONDITION(S):
Slip speed 48 rpm or greater for 4.5 seconds.

ACTION TAKEN:
1. PCM turns "ON" the "SERVICE ENGINE SOON" MIL.
2. TCC is disabled for the entire ignition cycle.

NOTES ON FAULT TREE:
1. Testing Torque Management Brake Switch input to the PCM P171. If test passes, the display will change from HI 0 to HI X. If test fails, the display will not change.
2. Checking for an open in CKT 420 between C112 and C201.