A Case of a Leaking Capacitor - Transmission Digest

A Case of a Leaking Capacitor

It is not uncommon to hear of a technician investigating the inside of a computer as part of a diagnostic routine, especially when dealing with odd continual electrical problems. Sometimes when the box is opened, a distinct burnt odor confirms the technician’s hunch that it was fried “Fred” causing the problem all along. Sometimes a cracked circuit board is the cause of those pesky intermittent trouble codes. On other occasions the box is filled with water from a leaking sunroof (Honda/Acura) or a leaking heater core (Mitsubishi/Hyundai), or it just had the misfortune of being in a flood.

A Case of a Leaking Capacitor

Technically Speaking

Author: Wayne Colonna, Technical Editor

Technically Speaking

  • Author: Wayne Colonna, Technical Editor

It is not uncommon to hear of a technician investigating the inside of a computer as part of a diagnostic routine, especially when dealing with odd continual electrical problems.

Sometimes when the box is opened, a distinct burnt odor confirms the technician’s hunch that it was fried “Fred” causing the problem all along. Sometimes a cracked circuit board is the cause of those pesky intermittent trouble codes. On other occasions the box is filled with water from a leaking sunroof (Honda/Acura) or a leaking heater core (Mitsubishi/Hyundai), or it just had the misfortune of being in a flood.

In 1992-95 Toyota Camrys with the 540E transaxle, a leaking capacitor corroding the TCM circuit board has proved to be a notable and consistent failure. It frequently reveals itself by producing solenoid codes with no upshifts when the transaxle is hot.

Figure 1 shows the TCM split open. A red circle identifies the area of the problem capacitor. Figures 2 and 3 are closer views. You can see the dark-brown electrolyte that leaked out below the capacitor and onto the circuit board.

Scotty West, of Auto Computer Exchange in Davie, Fla., said this leak sometimes is hard to detect, as it may begin with a clear-color leak before the dark brown is visible. Other times the leak will show up as white and green, especially if it has had some time to deteriorate the circuit board.

In instances in which this failure has been discovered before the circuit board has deteriorated, it’s possible to replace only the capacitor. This process requires the proper soldering equipment and the ability to accomplish this task successfully.

1990-1991 Lexus ES250 and ’92-93 ES300 also are subject to this failure.

In the LS400 and the SC300 equipped with the 340E rear-wheel-drive transmission, a different type of problem occurs when a similar capacitor in the computer leaks. One of the injectors fades in and out, and a cooling fan turns off.

Many thanks to Ritchie and John of Al’s Transmissions for the tip and the photos, and to Scotty West, who provided additional details. I also thank ATSG technician Mike Souza for putting this on my desk to write about it.

You May Also Like

Sherlock Holmes Approach to an AB60 No-Move Situation

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult.  Using scopes provides

ab60

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult. 

GM 6T40 Pump Identification Guide

The 6T40 was introduced in 2008 for General Motors front-wheel-drive cars in the Chevrolet Malibu and has gone through several changes throughout its three generations, specifically in the pump area. The 6T40 is closely related to the more lightweight 6T30 and the heavier duty 6T45 and 6T50. Generation one started phasing out during the 2012

Seeing the Forest AND the Trees

They say that the proverbial phrase “I couldn’t see the forest for the trees” means that a person or organization cannot see the big picture because it focuses too much on the details. Related Articles – 4L60E Harsh 1-2 Shift – TASC Force Tips: Diagnosing 8L45 & 8L90 Shift Complaints – TASC Force Tips: Hydraulics

The Manifold Pipeway

The Honda six-speed transmission has been on the bench of many specialty shops for one reason or another (figure 1). But, for those of you who have yet to lay your hands on one, mounted on the upper side of the unit is one of the largest, if not the largest solenoid and pressure switch

8L90 Vacuum Testing

Below are the diagrams for vacuum testing GM 8L90 transmissions. Note: OE valves are shown in rest position and should be tested in rest position unless otherwise indicated. Test locations are pointed to with an arrow. Springs are not shown for visual clarity. A low vacuum reading indicates wear. For specific vacuum test information, refer

Other Posts

Sometimes, a diagnostic code is all you need

With ATSG having the opportunity to help shops solve problems, sometimes we get faced with some real doozies. A shop will call and give us a laundry list of DTCs, leaving us to think someone must have a bulkhead connector unplugged. We then go through the arduous task of deciding which codes prompted other codes

10L80 and 10R80 pump gear differences

You may have seen an article in the August 2023 issue of Transmission Digest called “GM 10L80: A new kind of pump noise,” which goes over how the front cover housing in the 10L80 is fitted with a converter drive gear and idler gear. The idler gear drives the pump’s driven gear, and is press

Spotting different 68RFE designs through the years to avoid issues

The Chrysler 68RFE has had several changes through the years. Its four-speed predecessor began with a noisy solenoid pack identified by a black colored pass-through case connector (seen in Figure 1).  Related Articles – Going the extra mile: Proving your transmission repair suspicions – Diagnosing Ford 10R60, 10R80 and 10R140 series speed sensor issues – Jatco JF613E

Sometimes, you should sweat the small stuff

It’s a common phrase: There may have been a time when you worried about something, and someone who knew what you are going through said, “Hey, don’t sweat the small stuff.” Sometimes, this may be good advice. But other times, it may be wise to handle the small stuff before it becomes bigger “stuff.”  Related