CD4E Converter Clutch Codes ^©2001 Sonnax Industries Inc. By Bob Warnke, Sonnax Industries Inc. T he Ford CD4E and Mazda LA4A-EL often “come in or come back” with TCC slip codes of 628, 1740-44 or 741. An ounce of prevention is worth a pound of cure and, with this problem, those pounds are in parts and labor. Prevention in this case involves “seat of the pants” di- agnostics, with your pants on the car’s seat. Let’s assume this is a new job and start with the car, while finishing up at the bench. First, verify that the turbine-speed sen- sor and its signal are functional. These sen- sors are common to set repeat TCC codes at highway speeds. Illustration 1, an Hz graph, illustrates a defective new sensor signal. An experienced sensor is often the effective fix. The stall test explained below is not a WOT brake stall where the engine stabilizes at 2,500 rpm. The fol- lowing “engine kill or stumble” test isolates the TCC lining and hydraulic control. Shift Controller Stall test on TCC circuit (cool unit): • Remove the air-cleaner housing, wire retainer and transmission-case connection. • Clearing codes can be avoided by attaching a solenoid block (OEM circuit) onto the chassis harness. • Install the shift controller to the transmission. • Jumper wires are an option. They are time con- suming and alter the result because of no EPC con- trol. • Control EPC amperage to simulate OEM idle pressure. • Shift controller to 3rd gear (SS1 and SS2 off). • Position selector lever in D, idle at 750 rpm. • Command a two-second TCC apply (excessive test can cause TCC overload or solenoid failure). • Good converter: Engine will stall or near stall im- mediately on TCC apply (A 4-cylinder should stall, V- 6 near stall). • Weak converter: No noticeable change in rpm. Converter damper assembly often starts to rattle. • Verify thatTCC solenoid and CT (converter tur- bine) pressure are good. Road test with shift controller at operating tempera- ture: • Command TCC in 3rd with light acceleration and during deceleration. • Good Converter: Engine rpm should drop sharply and have engine braking during coastdown. At a stop, with brakes applied, command 3rd gear. Engine should pull down at least 150 rpm or cause stumble. • Weak Converter: No drop in engine rpm or felt engine braking. CT Pressure Test A worn pump or boosted pressure will reduce the converter feed. Both conditions can prevent engine stall. When the PCM is in failsafe the EPC pressure rises, limiting converter feed. Low converter feed will allow engine torque to pull through the slipping TCC piston and rpm will not drop. Low idle and low pump rpm reduce output. With a 4-cylinder, the stall and CT tests can be per- formed on the lot in about 30 minutes. On the V-6, lift time must be added to access the CT pressure tap. The CT plug is easily removed and is located to the left of the valve body cover, 2nd up from the cool- er-outlet line (See illustration 2). Reproduced with permission, Transmission Digest, September, 2001. For subscription information visit www.mdpublications.com