Technically Speaking
- Author: Wayne Colonna, Technical Editor
This is what Yosemite Sam might say if he were a transmission guy working on one of these vehicles. Well, maybe a few other carefully selected words would infiltrate that phrase if he experienced what happened to Anthony Bellino at Gibraltar Transmissions in Staten Island, N.Y.
A 1999 Daewoo Leganza with a 50-40LE transmission came into the shop with the driver complaining that the vehicle had no power. It was immediately discovered that the transmission was in a fourth-gear limp mode. The next step was to retrieve codes. The aftermarket scan tool the shop owns does not offer a specific Daewoo cartridge, so only generic OBD-II was available to them. And as you probably guessed, the scan tool reported that no codes were present.
So now the shop had a vehicle in limp mode with no codes. This sent them to the TCM (to the left of the steering column, attached to the firewall) to check for power and grounds, only to find that all was well. With the wiring diagram in hand, they checked as many of the TCM’s inputs and outputs as possible. Again, all was well. So now what? The shop found a used TCM for $150 and installed it, and if you are reading this with alacrity of mind, I know you know what the result was: no change.
At this time there was only one option left. Since GM had bought Daewoo, it was time to take the vehicle to a GM dealer and see what a factory scan tool had to say. It reported “no active codes.” The technician navigated the scan-tool controls to view history codes and discovered a P1702 “TCC Circuit Malfunction” code. The code was cleared and the vehicle was restarted. The scan tool reported “no active code,” but in history it found that P1702 was set again.
At this time the shop decided to clear the code and turn the ignition to the On position without starting the vehicle. With the scan tool in the active code display, the vehicle was started. Then, code P1702 popped up as an active code for just a second before it disappeared and filed itself into history.
With this discovery, the shop acquired a diagnostic tree for the code. The tree began with checking the entire circuit from the TCM to the solenoid inside the transmission. These checks had been performed earlier. The step following, however, is where Anthony hit pay dirt. There is a torque reduction wire that connects the TCM to the ECM (Figure 1). It was this wire that needed to be checked next.
The ECM on this vehicle is in the passenger-side kick panel and is positioned vertically, placing the three connectors plugging into it one above another (Figure 2). When they were unplugged, the cause was obvious. Water intrusion coming from deteriorated weather stripping found its way into each of the connectors (Figures 3, 4, 5 and 6). Cleaning the connectors was all that was needed to restore proper communication, eliminating code P1702. The weather stripping is another subject.
So what do you think Yosemite Sam might say after going through all this work, only to remedy the problem by simply cleaning connectors?
