DTC 39

Fig. 22 Transmission wiring circuit. 1984:

Fig. 23 Transmission wiring circuit. 1985:

The ECM completes circuit for TCC solenoid by grounding circuit 422. Grounding this circuit allows solenoid to energize and supply oil pressure to torque converter clutch. Code 39 indicates that ECM is seeing engine speed at a greater RPM than would be expected at 55 mph with TCC engaged. Possible causes of this condition are:
a. Defective TCC solenoid.
b. Defective TCC brake switch.
c. Defective wiring or electrical connectors.
d. ECM not able to properly process signals.

To diagnose a Code 39, proceed as follows:
1. Turn ignition on and connect test lamp between ALDL diagnostic connector pin F and ground.
2. If test lamp lights, proceed to step 3. If test lamp does not light, proceed as follows:
a. With ignition on and brakes released, check for voltage at both sides of TCC brake switch using a test lamp.
b. If test lamp does not light on either side of switch, check GA-TRANS fuse. If fuse is blown, replace fuse and repair ground in circuits fed by fuse. If fuse is not blown, repair open in circuit 3 or 39.
c. If test lamp lights on one side of switch only, check adjustment of TCC brake switch and adjust or replace as necessary.
d. If test lamp lights on both sides of switch, disconnect transmission connector and connect test lamp between pin A and ground. If test lamp lights, proceed to step 2e. If test lamp does not light, repair open in circuit 420.
e. Connect test lamp between pins A and D of harness connector. If lamp does not light, repair open in circuit 422. If lamp remains lit, check for loose transmission connector or open circuit in transmission.
3. If test lamp lights, proceed as follows:
a. Enter diagnostics and display Code .9.6. If test lamp remains lit, proceed to step 3b. If test lamp flashes in three second intervals, proceed to step 3d.
b. Disconnect transmission connector and measure resistance between pins A and D on transmission side of connector.
c. If measured resistance is less than 15 ohms, repair short in transmission circuit and verify that ECM has not been damaged. If resistance is greater than 15 ohms, check circuit 422 for an open. If circuit is satisfactory, check for faulty ECM or ECM connector and repair or replace as necessary.
d. Start engine, enter diagnostics and display parameter .1.2.
e. Drive vehicle at 55 mph. When TCC engages, the ``TCC'' status light will go on and test lamp will go out.
f. With test lamp off, display parameter .1.1 and ensure engine RPM does not exceed the following speeds at 55 mph: Eldorado and Seville except high altitude models, 1600; high altitude Eldorado and Seville, 1700; DeVille and Brougham except high altitude models, 1700; high altitude DeVille and Brougham, 1850.
g. If engine speed exceeds specifications, system is functioning normally and transmission is at fault.