344 Automatic Transmissions and Transaxles Copyright by Goodheart-Willcox Co., Inc. Ground connection Figure 14-7. Fusible links may be installed at the starter’s posi- tive terminal. A melted fusible link is sometimes hard to spot, since fusible links often melt open without damaging the insu- lation. Always tug at the fusible link to make sure it has not opened internally. Figure 14-8. Bad grounds are a common source of trouble. Always check grounds by visual inspection and by pulling on the connec- tions. Also try to tighten the attaching bolt when applicable. Step 6. Correct the defect—Repair or replace the defective components as necessary. Step 7. Recheck system operation—Road test the vehicle to make sure that the problem has been corrected and that no trouble codes have reappeared. If necessary, review the detailed explanation of the seven-step process in Chapter 13. Remember that on mod- ern vehicles, almost all systems are interconnected and affect each other. Is the Trouble in the Electronic Control System? Electronically controlled transmissions and transaxles may have problems caused by the mechanical and hydraulic components. Slipping and erratic shifting are as likely to be caused by hardened or damaged seals or burned hold- ing members as by defects in the electronic control system components. To isolate the problem to the mechanical, hydraulic, or electronic components, you must conduct some of the same tests used when checking hydraulic systems and com- ponents. Always begin any test procedure by removing the dipstick and checking fluid level and condition. As with a hydraulically controlled transmission or transaxle, this may give you all the information you need to diagnose a problem. Also check the manual linkage for looseness and proper positioning. On a few electronic transmissions, some of the shifts are hydraulically controlled. On these transmissions, check the adjustment and condition of the throttle linkage, and check governor operation. When you perform a road test, note the condition of the engine and other vehicle systems, as well as the operation of the transmission or transaxle. A miss, surge, hesitation, or other problem may be mistaken for a defect in the transmis- sion or transaxle. Engine missing and lockup torque converter shudder are often confused. Occasionally noises or roughness in the suspension may be blamed on the drive train. If the preliminary checks lead you to believe that the problem is in the electronic control system, proceed with the diagnostic procedures that follow. Basic Electrical Checks Before performing complex electronic tests, make some basic electrical checks. Begin by ensuring that the system fuses are not blown. Note that there may be more than one fuse protecting the system. Note: Do not remove any fuses until you have retrieved trouble codes from the ECM. Next, make a careful inspection for burned, chafed, and disconnected wires. In some cases, the wiring harness wrapping may have to be pulled back to expose damaged wires. Be sure to look carefully for burned insulation at any fusible link, Figure 14-7. Pull on the link to determine whether the wire has broken internally. Fusible links are usually located at the battery positive terminal, a nearby power relay, or the starter solenoid. Check all vehicle ground wires. See Figure 14-8. On many vehicles, several ground wires are attached to one of the bolts on the engine thermostat housing. Slight coolant leaks can cause these wires to corrode. Often, the ground wires are removed during cooling system service and never reattached.