A/T - 4L60E Diagnosis Trouble Code 72 Chart - C: Overview
TECHNICAL BULLETIN # 302A PART 2DATE 1995
TRANSMISSION: 4L60-E
SUBJECT: Code 72 diagnosis, Chart C
APPLICATION: GM
4L60-E Code 72 Diagnosis Chart C
This Bulletin is designed to supplement the previously released 4L60-E Code 72 diagnostic strategy bulletin, numbered 302.
Concerns common to all applications:
^ Excess grease packed into a connector. An excessive amount of grease in a terminal connector can cause poor electrical contact.
^ The toothed-wheel for the VSS is loose on the output shaft.
^ Extension housing or output shaft bushing is loose.
^ Someone has added a ground for an add-on accessory, such as an alarm or two-way radio, to the PCM or DRAC (VSS buffer) ground circuits.
^ An add-on accessory, such as an alarm or radio, is located too close to the DRAC which can cause electro-magnetic interference problems. This condition may be indicated by noting a speedometer reading with the vehicle sitting still while the add-on device is powered up.
^ Vehicle speed sensor, DRAC or PCM is faulty.
^ Loss of terminal pin tension for the female terminals in any connector. All terminals are designed to withstand only a few connects and disconnects. Connecting and disconnecting the system's connectors will reduce the life expectancy of those terminals. This can allow an intermittent connection to occur. Loss of pin tension will cause damage to most terminals. To check for proper pin tension use the appropriate terminal tension gauge or use a spare male terminal of the correct size. To check the PCM and DRAC terminals use a .039" drill or carburetor gauge. Both the PCM and DRAC use micro-pack terminals (round). Simply feel for a moderate drag when the male pin is inserted and removed. Be sure to use the correct size and style of male terminal when testing for pro per tension.
COMMON CONCERNS SPECIFIC TO MODEL
^ Safari and Astro Vans
^ S-10/T-10 Truck, Blazer and Jimmy.
^ C/K - Full Size Pickup, Yukon, Tahoe, Suburban and Blazer
^ Series, Full-Size Van